Anton/Bauer Hytron 50 Specifications

Anton/Bauer Hytron 50 Specifications
THE VIDEO BATTERY
HANDBOOK
The worldwide standard ®
Table of Contents
Introduction
1
Voltage
5
Voltage Technical Section
Capacity
Capacity Technical Section
Battery Construction
Construction Technical Section
Battery Design Features
Cell Formulation
Charging
Charging Technical Section
7
10
12
16
17
19
22
27
28
Battery Life
37
Safety Hazards
40
Portable Lighting
44
Problem Appendix
47
Technical Update: Fuel Cells
54
THE VIDEO BATTERY HANDBOOK
Anton/Bauer has distributed more than 150,000 copies of the Video Battery Handbook since its
initial publication in 1993. As the definitive guide to the care and feeding of video batteries it
has been used as a reference and as a teaching aid in film and video courses in many schools
and universities.
This is the fourth revision of the VBH and we have made every attempt to relate the up to date
information on the battery chemistries used by professionals on the latest equipment in the video
industry today. This Handbook is not meant to be a technical primer on battery chemistry, but a
guide for videographers to better understand one of the least understood, yet most essential
elements of a portable video operation.
In the three decades since television cameras began to leave the studio, both video and
battery technologies have dramatically improved. Yet the batteries remain invariably at the
top of the list of issues with today’s video operations.
Today the boom in personal electronic devices – PDAs, MP3 players, cell phones with color
LCDs and cameras, notebook computers – are all looking for improved power solutions.
This search leads to headlines of new power sources – plastic batteries, exotic chemistries,
super capacitors, even fuel cells.
Introduction
Smaller, lighter, more powerful, less expensive - who hasn’t heard these wishes from a battery
user, or as claims from a battery manufacturer? In fact, in all portable equipment markets,
batteries are the number one area in which customers would like to see improvements. In the
computer and cellular telephone markets, requests for improvements in battery life (runtime)
and weight/size come before processing speed and cellular coverage. Of course, the broadcast
and professional video industry is no exception.
If only these devices were the same as a professional video camera. Most new cell types
address the size and weight issues for mobile communications and computing products.
Rightfully so since the market size for these products are several orders of magnitude greater
than all camcorders, consumer to broadcast, put together. The manufacturer who could
design a cell to be used in a battery for notebooks and cell phones was designing a product
for the largest growth markets the battery industry had ever seen. Size and weight are
paramount in mobile communications and computing to the exclusion of all other
considerations – like performance and life. Very seldom does anyone keep a cell phone long
enough to require a new battery. The publicity these new technologies receive in mobile
communications and computing make them seem like the answer to all battery problems.
Over the years, the quest for the “perfect” battery has led to many unsuitable battery types
being marketed over the years - batteries of incorrect voltage, unsuitable size and insufficient
packaging fail to meet the requirements of a video professional. But because these batteries
were touted as “smaller, lighter, cheaper” and because the uninformed view is often that “a
battery is a battery”, these products were purchased thinking that they would be suitable for a
professional. Many of these were brought up by equipment manufacturers from consumer
1
products to allow the manufacturer to offer a turn-key camera package. Professionals soon
found out that problems with these batteries were insurmountable. Terms like “memory” were
coined to explain the inadequate operation of poorly designed and/or misapplied batteries.
Once invested in a poor power solution, users looked for ways to salvage their bad battery
investments. For example, we are all familiar with the variety of rejuvenators, reconditioners,
de-memorizers, revitalizers and other such gadgets marketed in an attempt to salvage the
large inventories of NP batteries in the marketplace. Well after investing thousands of
dollars and hundreds of hours of maintenance time on their NP batteries, users found out too
late that poor design and misapplication problems never really go away. Thus, to this day an
NP user typically carries up to 4 times the amount of batteries that should actually be needed
and replaces them twice as often.
Ever since the NP battery was introduced on the first BetaCams, users were looking for a
way to “fix” them. Over the years this futile effort unfortunately was like trying to fix a
mis-registered camera by buying a new lens. (Ironically the NP battery, originally an audio
battery 30 years ago, to this day survives in the industry mainly as an audio mixer battery
due to its size and the low power requirements of audio receivers and mixers.)
Introduction
The quest for the “Holy Grail” of portable power has taken its most recent turn in a great
deal of hype surrounding the current state of fuel cell technology and the coming hydrogen
economy. The viability of fuel cells in portable video is discussed later in a technical update.
Today the impression is that all batteries are, or at least should be, some exotic formulation...
It is simply not so....
Let’s get a perspective with some irrefutable facts:
(1) Outside of cell phones and notebook computers, whose power requirements are a
fraction of the power demands of portable professional video, NiCd and NiMH cells
account for about 70% of the world market in rechargeable batteries. It is simply so
because no other chemistry is capable of providing the current carrying capability of
nickel based cell chemistry.
(2) About 70% of the NiMH and lithium ion cells produced are manufactured in small sizes
(AAA and small rectangular chewing gum stick sizes) for mobile communications and
computing. These size cells are not adaptable for professional video applications. Their
small size and high internal impedance make them useless for the power demands and
environmental conditions of video field production.
(3) A typical notebook computer draws less than 1 amp (with hard drive and back lit color
LCD screen) usually at 12 volts or about 10 watts.
(4) A typical cell phone draws less than 1/2 amp at typically 5 volts or around three 3 watts.
2
(5) Aside from power tool and video there are few other applications where the batteries are
not integral to the equipment. In other words a typical cell phone battery or computer
battery will see only one device in its entire life under relatively fixed operating ranges for
load, temperature and charging.
Now let’s understand some of the criteria for professional video batteries:
(1) Today’s average camcorder draws about 24 watts in record; a professional mini-DV
camcorder may draw as low as 18 watts. Many new non-linear camcorders as well as high
definition cameras, draw almost double (45 watts or more) that of the average
camcorder. (Oddly enough 20-45 watts has been the power range of cameras for the last
15 years.)
(2) Non-linear acquisition (disk, DVD, solid state memory) in theory require infinite runtime.
First they typically have a long “boot up time” so that they run almost continually in
practice. Second, since the recording can be selectively “saved” the camera can be
recording constantly thus theoretically requiring a battery which lasts for as long as the
camera can be in operation.
(3) The typical on-camera light used today draws 25-50 watts. The typical focusable or
dimming type light will always draw 50 watts.
(5) Nearly 2/3 of the weight of a camcorder (with lens) is forward of the center of gravity
point- typically the physical center line of the camera – therefore, most of the weight is in
front of the camera. Balance NOT weight is an overriding ergonomic consideration on a
camcorder. Not compensating for this forward weight has been determined as the cause
of fatigue and back strain for cameramen. Although cameras are getting smaller and
lighter, camera lenses always remain out front, thereby unbalancing the camera. A 3-5
pound (1.5-2.5kg) battery actually balances today’s camcorders perfectly while a lighter
battery will actually add to the fatigue factor.
Introduction
(4) New formats have recording times on a single medium of 60 to 120 minutes or more an
increase of 3 to 6 times over 10 years ago. Therefore, the power necessary to record a
single tape has increased by 3 to 6 times.
(6) A typical professional video battery is often used on several pieces of equipment –
cameras, monitors, editors, lighting – and often used by a number of different operators
under an extremely wide range of operating conditions.
The answer to the question, “Why aren’t all these new battery types used for my camcorder?”, should now be clear: A professional camcorder used by a video professional has very
different power and ergonomic requirements than a cell phone, a digital pocket camera, an MP3
player or a PDA used by an accountant. If a portable enterprise wants to remain portable, then
batteries – cost efficient, powerful, long lasting and reliable ones – will continue to be part of the
logistics of a video operation.
3
The following discussion concentrates on full size professional video cameras where the user
has a choice of battery types and performance options.
Introduction
This guide will discuss the elements essential in determining the proper battery and charger system
for a modern professional video operation. We have included additional technical sections for those
who wish a more in-depth explanation. Another section deals with the aspects of on-camera
lighting, an important factor both in battery selection and quality video production.
4
VOLTAGE
There is ironically still confusion concerning the proper voltage battery for an application. The
confusion is due to the popular but incorrect practice of referring to a battery or camcorder
by a single voltage. References to a “12 volt battery” or a “12 volt camera” do not refer to
average voltage, nor do they signify minimum or maximum voltage. These numbers are called
‘nominal’ ratings, which are merely convenient ‘names’ for these devices and have absolutely
no relevance whatsoever to a specific application.
In actuality, every battery and every camera has a voltage range over which it operates. The
process of matching the correct voltage battery to a piece of equipment simply requires that:
The full operating range of the battery must fall totally within the
operating range of the equipment being powered.
The first step is to establish the accurate voltage range of your equipment. If you have the
instruction or technical manual, turn to the specification section and find the ‘Power’ entry.
Hopefully you will find one of the following type entries:
VOLTAGE = 11-17 volts
or VOLTAGE = 12(-1,+5) volts
OR
POWER = 24 WATTS @ 12 VOLTS (-1V, +5V)
Voltage
In each of these cases the range of the device is 11 to 17 volts. Specifically, below 11 volts the
device will cease to function properly (in some cases a camcorder or VTR will unthread or
drop out of record below this voltage). Likewise, voltages above 17 volts may damage the
equipment or, more likely, blow a fuse or breaker.
If you no longer have the technical manual, or Power entry has a single number such as:
VOLTAGE =
12 volts DC
or
POWER = 24 watts
You will have to determine the voltage range by other means. One method is a simple phone
call to the equipment manufacturer. Talk to an engineer and give him your precise model
number. Our experience has shown that in order to avoid confusion, the voltage range will be
best determined by asking the following two questions:
1. “What is the lowest voltage I can supply to this device before quality or
performance is adversely affected?”
2. “What is the highest voltage I can apply to this device without causing
damage or blowing a fuse?”
Once the voltage range of your equipment is accurately determined, the next step is to establish which voltage battery has a range that falls totally within the range of your equipment.
The voltage range of batteries typically used in the video industry is as follows:
5
“12 volt Nominal”
10 cells NiCd or NiMH
Range = 10 - 14 volts
“13 or 13.2 volt Nominal”
11 cells NiCd or NiMH
Range = 11 - 15 1/2 volts
“14 or 14.4 volt Nominal” Range = 12 - 17 volts
12 cells NiCd or NiMH or 4 cells Lithium ion
Voltage
Matching the correct battery to your equipment is now straightforward. As an example,
consider the typical technical manual entries above that listed the power range as 11 to 17
volts. In this case both the “13.2 volt” [11-15 1/2] and the “14.4 volt” [12-17] batteries have
ranges totally within the equipment specification and are therefore fully compatible. In cases
such as in this example where more than one battery is applicable, the best run time and
reliability will always be achieved with the higher voltage battery. Note carefully that the
range of the “12 volt” [10-14] battery extends below that of the equipment and is not
compatible. In addition to the above, the following general facts may also prove helpful for
proper voltage selection:
1 - A “12 volt nominal” battery should never be used with modern video equipment. This is
due to the fact that virtually every piece of professional video equipment designed in the last
10 years has a minimum voltage requirement of between 10.5 and 11.0 volts. Thus the 10
volt full discharge rating of a “12 volt nominal” battery is significantly below the minimum
voltage requirement of all professional video equipment. (VTR batteries with cables such as
BP-90 types and NP-1 types should be particularly avoided. See Technical Section)
2 - A “13.2 volt nominal” battery can operate virtually all professional video equipment.
This is based on the fact that all video equipment specify a maximum voltage of 15.5 volts or
higher, and a minimum voltage of 11 volts or lower (down to 10.5 volts). Thus the 11 to 15.5
volt range of a “13.2 volt nominal” battery falls totally within the operating range of virtually
any video equipment which may be in use today. However, it should be noted that the performance and runtime of equipment can be unnecessarily limited by using a 13.2 volt battery
which will not take advantage of the additional power and performance of a 14.4 volt battery.
3 - A “14.4 volt nominal” battery can be used with any equipment which specifies such a
battery or has a maximum voltage rating of 17 volts or higher. A “14.4 volt nominal” battery
will provide better performance and life relative to a comparable “13.2 volt” battery. This is
true especially when selecting a NiMH battery or a small size battery whose smaller size cells
have a higher internal resistance, thereby limiting its cold weather or high drain rate
performance. Make sure your equipment can accommodate voltages as high as 17 volts
before using a “14.4 volt” battery. As a rule, virtually all professional equipment now being
manufactured are specified to deliver optimum performance with “14.4 volt” batteries.
Please feel free to contact Anton/Bauer Customer Support. An Anton/Bauer support technician can
tell you which voltage and type battery will deliver optimum performance with your equipment.
6
VOLTAGE TECHNICAL SECTION
BATTERY VOLTAGE RANGE
While the ‘nominal’ voltage rating is technically meaningless, battery “range” limits are very
significant. When a fully charged battery is first placed on a piece of equipment and power is
turned on, the initial voltage may be as high as the upper range limit. Typically the voltage
will drop quickly during the first few minutes of discharge, then continue to drop more slowly
throughout the rest of the discharge cycle until the voltage reaches the lower range limit at
which point the battery has released all its stored energy. The shape of this discharge curve
and the rate at which the voltage drops is dependent on many factors including the power
drain rate, battery size, age, temperature, and cell formulation. (See fig. #2) However,
regardless of the shape in between, the lower limit remains the same and is called the
‘End Of Discharge Voltage’ or EODV by the cell manufacturers.
This EODV is the most critical voltage rating of a battery, and the only voltage specification
stated by the cell manufacturer relative to capacity. This is the voltage down to which a
battery must be taken in order to retrieve 100% of the available capacity. To put it another
way, the cell manufacturer will guarantee full capacity only if the battery is discharged down
to the EODV. Conversely, you can not get all the energy out of the battery until it is
discharged to this voltage. Therefore, if the lower range limit of the battery (EODV) is below
the lower operating voltage limit of the equipment, you will never get the full capacity or run
time out of the battery.
Voltage
Figure #1 clearly illustrates the problems of
powering a modern piece of video equipment with
a battery of improper voltage. In this example, the
10.0 volt End Of Discharge Voltage (EODV) rating
of the “12 volt nominal” battery is significantly
below the 11 volt minimum or “cut-off” voltage of
the professional camcorder. Only a 13.2 or 14.4
camera battery fully conforms to the operating
range of professional video equipment.
Figure 1
The discharge curve ‘A’, in figure 2, is typical of a “12 volt” NiCd battery in mid-life. Note that
this battery is perfectly within specification and still delivers close to 100% of its rated capacity
at its specified EODV of 10 volts. However, the camcorder can NEVER make use of all this
power because as soon as the battery voltage falls below 11 volts, the camcorder ceases to
operate. The battery appears to have ‘lost’ 25% of its capacity. In reality the rest of the energy
is still in the battery, but the camcorder just can’t get to it. This is called “unavailable
capacity” and is totally due to a battery voltage mismatch with the equipment.
The resultant phenomena has become commonly and inaccurately known in NiCd chemistry
as “memory” (see also “memory” in the Problem Appendix) is illustrated by curve ‘B’ where it
is apparent that “memory” is actually a “voltage depression” phenomena. At the so-called
“memory” point the voltage suddenly drops about 1.2 volts, where it is once again below the
camcorder cut-off voltage. The camcorder stops and it appears that “memory” has caused a
50% loss of capacity. But if you look again, it is not really a loss of capacity. The battery will
still deliver close to 100% capacity within the EODV voltage specification.
7
Curve ‘C’ represents a mid-life NiCd in cold weather. In this case the battery will run the
camcorder for only 25% of its normal time. Again, there is nothing wrong with the battery.
Curve ‘C’ is fully within the normal NiCd operating specifications yielding rated capacity at
the EODV of 10 volts.
In all of these instances cameramen usually blame the apparent loss of capacity and run time
on the battery ‘getting old’, that strange “memory thing”, or the cold weather. Considering
these curves, it is easy to understand why “12 volt” batteries seem so unreliable. Depending
on prevailing conditions you never know exactly how much run time you will get from a
battery. In reality all three of these losses of capacity are due solely to the operator using
the wrong voltage battery.
Voltage
Curves ‘D’, ‘E’, and ‘F’ represent the discharge curves of a “14.4 volt” battery under the
identical three conditions and with the identical camcorder. As if by magic the “getting old”,
“memory”, and cold weather problems suddenly disappear. Why? Because the 12.0 volt
EODV or full discharge voltage rating of the “14.4 volt” battery is properly above the 11
cut-off voltage of the camcorder. The curves of a “13.2 volt nominal” battery with an EODV
of 11.0 volts would also deliver 100% capacity in all these cases.
Small size batteries are constructed typically of
smaller cells and have greater internal resistance
which also results in a significant lowering of the
voltage curve, especially under higher loads or cold
operating temperatures. This also results in a
significant loss of run time regardless of voltage
level and a very severe loss of capacity in the
above examples.
Because of the unique nature of lithium ion
chemistry, batteries constructed with these cells can
Figure 2
only be made into batteries in multiples of the
generally nominal 3.6 volts of each cell (i.e. 3.6,
7.2, 10.8, 14.4, 18 volts, etc.). A 10.8 volt (3 cell) battery would be insufficient to operate
a nominal 12 volt camera and an 18 volt (5 cell) battery would over-voltage the camera.
Therefore, to power a professional 12 volt nominal cameras, lithium based chemistries can
only be constructed in batteries employing four cells or 14.4 volts nominal. Considering the
attention that lithium ion has received in the past few years, it only contributes to the voltage
irony – lithium ion can only be used for a 12 volt nominal professional video camera in a 14.4
volt configuration.
However, it should also be apparent, then, that the loss of a single cell from a lithium ion
battery will render the battery incapable of operating a camera.
In the old days NiCd batteries were often rated at the “plateau voltage” of the battery defined as the voltage at which the battery stays at for the longest time during discharge.
Technically, the “operating voltage” of a battery is correctly defined at the midpoint of its
discharge – that is if the battery runs for an hour then the voltage of the battery at the 30
minute mark is its “midpoint voltage”. For a NiCd (or NiMH battery for that matter) this is
8
nominally 1.2V/cell, therefore giving rise to the 10-cell 12 volt battery, 11-cell 13 volt (13.2 V)
and 12-cell 14 volt (14.4V) nomenclature. All this, of course, is at nominal temperatures, loads
and service life. But generally speaking the battery will have an operating voltage of (1.2V X #
of cells in series) for most of its service life.
Lithium ion is different from NiCd (and NiMH) in many characteristics. Operating voltage is
just one of the differences. The voltage profile of li-ion changes over its life. All these changes
are attributed to the increase in the internal resistance of the cell which increases over
calendar time and over the number of charge/discharge cycles the battery experiences.
The voltage at which a lithium ion cell
operates is approximately 3.6-3.7 volts
midpoint voltage. Therefore, you could rate a
4 cell series battery from 14.4 to 14.8
– a difference of about 3%. BUT as the graph
shows, the operating voltage, as well as the
capacity of the battery, deteriorates
significantly over the number of cycles - unlike
nickel based chemistries where operating
voltage remains relatively constant over the
battery life.
Cycle Characteristics (Discharge Characteristics)
The “ratings game” used to be played by calling a battery 12 volt battery 4 Ah and equating
it to a 4 Ah 14.4 volt battery suggesting that the “capacity” or runtime would be the same
because the ampere hour “rating” was the same (see Capacity section below)
Voltage
Now one needs to remember the calculations for capacity in watt hours:
WH = Operating voltage X capacity in ampere hours (Ah)
To clarify this Anton/Bauer pioneered the use of the more technically correct “watt hours” in
video batteries, long before it became commonplace in the general battery world.
Enter lithium ion. Now, battery manufacturers can use the “nominal operating voltage” of a
lithium ion cell to increase the advertised watt hours of their battery by 3% - without ever
doing anything to the actual performance of the battery! Theoretically using the exact same
construction of 2.1 Ah 18mm X 65mm cells from the same supplier, one battery
manufacturer could call the battery 90 Wh and another could call their battery 94 Wh. Both
would be technically correct but, assuming all other things are equal, the batteries will
operate equipment for the same runtime. Moreover, the graph shows clearly that very quickly
during the life of the battery that initial rating deteriorates rather dramatically.
Bringing us to our next characteristic – CAPACITY.
9
CAPACITY
There are many video professionals who have unwittingly crippled their field production
capabilities by selecting the wrong capacity battery for the wrong reasons.
Video is very different from almost all other battery applications. A cameraman functions
through his eyes and is comfortable only when he can ‘see’ through his camera. A film
cameraman could look through his camera all day without a battery even being attached.
But unlike a film camera, you can not ‘see’ through a video camera unless it is turned on and
drawing full power. A video camera is always drawing power while the cameraman sets up his
shot or waits for a politician to step outside of the capitol building. The power consumed by a
video camera therefore has absolutely nothing to do with the number of video cassettes or
disc space being consumed. A cameraman can often run through an entire battery before
recording a single minute of tape or saving a single minute of video to disc. The critical
consideration for video is the amount of time a battery can run a camera or camcorder.
The vital question when selecting a video battery is this: “How long should the equipment run
between battery changes?”
Capacity
The answer is a simple but emphatic: at least 2 FULL HOURS.
This two hour rule is the fundamental basis for selecting a battery for a professional video
application: This is not an arbitrary or capricious guideline but rather a very serious
specification which is based on extensive analysis of hundreds of professional
video operations. It is also based on a purely logical objective - to minimize battery
change disruptions.
Surveys of video professionals have indicated conclusively that more than one battery change
disruption per morning/afternoon is unacceptable. One battery change interruption can be
reasonably anticipated and is deemed manageable. However, two or more are perceived as
random disruptions that seriously impair production efficiency and result in lost time and
shots. The ultimate battery system is thus 4 batteries capable of operating for 2 hours and a
four-position charger. Start the day with battery #1. Mid morning change to battery #2 if
necessary. At lunch-break change to battery #3 (even if #2 is not fully depleted). Mid
afternoon change to battery #4 when necessary. The result is a maximum of one interruption
per morning/afternoon. But in order to assure this simple and efficient routine, the battery
must be capable of running the equipment for a minimum of 2 hours.
A one-hour battery, by contrast, involves a very complex system of 10 batteries, 3 chargers,
and the chaos of as many as 8 interruptions per day (see Technical Section). The classic
reasons for making this mistake include the desire for a ‘small’ or ‘light weight’ battery. As the
Technical Section explains, properly sized batteries can actually balance the camcorder better
for less operator fatigue, and weigh less and cost less than the equivalent amount of smaller
type batteries. Insufficient capacity can cripple a video operation. Start with the correct,
efficient, and economical 2-hour battery for your application.
10
Determining the proper 2-hour battery for any application is simple. Capacity refers to the
total power a fully charged battery can deliver and is properly measured in “watt hours”
(not “ampere hours”, see Technical Section). To determine the proper capacity of a 2-hour
battery for any application merely take the power rating of the camera or camcorder and
multiply by 2.
2 x Camcorder Power (Watts) = Battery Capacity (Watt Hours)
As an example, assume your technical manual or the label on your camcorder states “Power
Consumption = 26 watts”. The proper battery for that camcorder should have a minimum of
2 x 26 or 52 watt hours of capacity. After this calculation, select from those batteries with
capacity ratings of 52 watt hours or greater. The following additional points should also be
considered:
• Most professionals use small ‘fill’ lights on their cameras to remove foreground shadows. Most new cameras and camcorders come from the manufacturer with provision to
power such lights from the camera battery. These lights are popularly used for indoor available light situations (see Lighting Section). When using these lights, select a battery with
slightly higher capacity.
Capacity
• In a true battery system there should be a variety of battery sizes and capacity from
which to choose. This variety allows the professional to choose the appropriate battery to fit
the shooting situation much the same way as he can choose lenses, filters and lighting. For
example in the Anton/Bauer InterActive system, batteries from 45 to 160 watt hours can be
used for different situations. For example, a small 50 watt hour battery can be used as an
easy to carry spare, while the primary battery can be a 160 watt hour high capacity type to
provide maximum runtime and performance. In this example, almost six hours of runtime
(almost an entire working day) can be had from the 160 watt hour battery while the 50 watt
hour pocket battery provides a “back-up” and minimizes the cost and number of larger
batteries which need to be carried to a shoot.
• Battery capacity will fade somewhat with age. Cell manufacturers typically consider a
battery to be within specification if it delivers 75% of rated capacity and define “end-of-life”
as a capacity reduction of 50% from intial capacity. Therefore, do not cheat on this ‘2 x
power’ formula as the mid-life capacity of the battery may decrease by 20% while a more
severe loss of capacity may occur later. Nickel based chemistries will tend to exhibit a
“plateau of capacity” for most of its life losing capacity rapidly over the last 10% of its life
until it is unserviceable. Lithium ion batteries exhibit a linear life profile and lose capacity over
their life a little bit each time it is used.
• The capacity rating of a battery is a “theoretical optimum” number. It is not like the
gallon capacity of a gas tank in your car. Choose your charging system very carefully (See
Charging Section). The actual capacity of a battery is totally dependent on the recharging
process. Depending on the type of charger and prevailing conditions, a so-called ‘charged’
battery may fail to provide even 1/3 of its ‘rated’ power. You can not think ‘battery capacity’
without thinking ‘charger’.
11
CAPACITY TECHNICAL SECTION
The topic of capacity is technically more complex than the simple rating number would
suggest. Like voltage, the capacity rating is “nominal” and in practice the actual amount of
energy a particular battery can deliver to a camcorder can vary over a wide range depending
on a multitude of parameters and conditions. This section will provide a better understanding
of the most significant elements that can affect the available capacity of a battery and the run
time of your camcorder.
Watt hours or Ampere hours? - The most classic cause of confusion involves the units used
to rate battery capacity. While cell manufacturers rate individual cells in “ampere hours”, the
proper unit for the measurement of energy in a group of cells (the definition of a battery),
is the “watt hour”. This is quite evident since watts are the unit of power and hours are the
unit of time. The outdated practice of rating a battery in ‘ampere hours’ is both incorrect
and misleading.
Capacity
As an example, assume a “12 volt” battery and a “14.4 volt” battery are both rated at 5
ampere hours and are to be used with a device that draws 24 watts. Given that both batteries
have the same “capacity” of 5 ampere hours, one would conclude that both batteries will
run the device for an identical length of time. But this is not true. The “nominal” watt hour
capacity rating for each of these batteries is calculated as follows:
“12 volt / 5 AH” Battery Nominal Capacity = 12 (volts) x 5 (AH) = 60 Watt Hours
“14.4 volt / 5 AH” Battery –
Nominal Capacity = 14.4 (volts) x 5 (AH) = 72 Watt Hours
The nominal run time is calculated by dividing this capacity rating by the
power of the equipment:
60 Watt Hours ÷ 24 watts = 2 1/2 Hours Run Time with “12 volt” Battery
72 Watt Hours ÷ 24 watts = 3 Hours Run Time with “14.4 volt” Battery
Thus the “14.4 volt” battery will provide a minimum of 20% greater run time compared to a
“12 volt” battery with the identical ‘amp hour’ rating – without the problems associated with
12 volt batteries. It should now be evident why the ampere hour rating is misleading.
Always compare and select batteries using ‘Watt Hour’ ratings. From the above example it
also should be clear that you can determine the nominal run time of any battery by simply
dividing the Watt Hour Rating of the battery by the power draw in watts of the equipment.
Testing Capacity - Many technicians make the common mistake of testing battery capacity
by discharging through a load resister or light bulb and using the number of minutes to fully
discharge the battery as an indication of capacity. Unfortunately this method produces highly
erroneous results. An example will best demonstrate the fallacy of using discharge time as an
indication of capacity:
12
Two NiCd or NiMH batteries are to be tested for capacity, one is a ten cell ‘12 volt’ while the
other is a twelve cell ‘14.4 volt’. Both fully charged batteries are discharged on a load resister
or light bulb with a resistance of 3 ohms. The ‘12 volt’ battery runs a full hour (60 min) while
the ‘14.4 volt’ runs only 55 minutes before reaching their respective EODVs. Most technicians
would conclude that the ‘14.4 volt’ battery had almost 10% less capacity than the ‘12 volt’
battery. In reality this test proves the ‘14.4 volt’ battery actually has 32% more capacity than
the ‘12 volt’ battery.
Using the basic formula I=V/R (current equals voltage divided by resistance), the ‘12 volt’
battery was being discharged at 4 amps by the 3 ohm resister while the ‘14.4 volt’ battery
was being discharged at the higher rate of 4.8 amps by the same 3 ohm resister. Taking the
broad liberty of using the ‘nominal voltage’ rating as an ‘average voltage’, the capacity of the
‘12 volt’ battery would be calculated by multiplying ‘12 volts’ by the 4 amps discharge
current times the one hour duration:
‘12 volt’ battery capacity = 12.0 x 4.0 x [60/60] = 48 watt hours
Similarly:
‘14.4 volt battery capacity = 14.4 x 4.8 x [55/60] = 63.4 watt hours
Capacity
Thus while the discharge test seemed to indicate that the ‘14.4 volt’ battery had less capacity,
in reality it had greater than 30% more capacity and would run a camcorder more than 30%
longer than the ‘12 volt’ battery. This timed discharge test is equally misleading for lighting
applications since the higher voltage battery not only raises the wattage rating of a given
bulb, but also increases the lumens/watts efficiency of the bulb. Thus, for a given fixed level of
illumination, the ‘14.4 volt’ battery would also provide longer illumination time than the ‘12
volt’ battery.
Simply remember, battery discharge data must be rendered into Watt Hour Capacity otherwise it is totally irrelevant and misleading.
Rated Capacity - The capacity rating of a battery is extremely dependent on the rate of
power drain. In addition to the aforementioned EODV, every cell manufacturer always
includes a current specification with the capacity rating such as “5 ampere hours (or 5000
milli – ampere hours) @ 5 ampere current drain”. This specific example is called the “C” rate
or “One-Hour” (discharge or charge) rate. In other words, the battery will deliver “5 amps for
one hour”. Because of internal resistance and other factors, the effective capacity will be less
at greater current drains. Conversely the effective capacity will be greater for lower current
drains. In the above example, this same cell may be rated: “5.5 ampere hours @ 1 ampere
current drain” which is the “C/5” or “five-hour rate” capacity. Likewise the “C/10” or “
ten-hour” rating may read: “5.8 ampere hours @ 1/2 amp current drain”. Cell manufacturers
will typically use one of these three standard rates to specify capacity. Virtually all lithium ion
and small NiMH cells are rated at the C/5 rate. Since this discharge rate makes the cell
“appear” to have higher capacity.
The “Numbers Ratings Game” - Note from the above that the cell appears to magically
gain capacity as you go from the ‘one-hour’ to the ‘five-hour’ and then to the ‘ten-hour’
rating method. Some battery manufacturers use this ‘magic’ to make their batteries sound
like they have more capacity. The rating of cells by cell manufacturers today, especially the
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newer NiMH and lithium ion chemistries, tends to have little bearing on the accurate
appropriate rating of batteries for professional video. These chemistries, have been designed
for and used primarily in relatively low power requirements. Therefore, the cell manufacturers
specify the capacity of these chemistries at the C/5 rate.
However, when these chemistries are applied to the much higher power requirements of
video equipment, the cell rating cannot be used to rate the batteries accurately and honestly.
Because the cells are typically smaller in size and the construction of these chemistries exhibit
high internal resistance, as the current draw is increased the available capacity of the battery is
dramatically reduced. By way of example, “4/3A” size NiMH cell rated at 4000mAh (4Ah)
discharged at the C/5 rate (800mA) will deliver only about 3500 mAh at a C-rate (4A)
discharge. Limited by an internal resistance typically 10 times that of NiMH and NiCd, this
phenomena ratings game is widely seen played in lithium ion cells and and batteries.
Capacity
Theoretically and ethically, a battery should be rated using the method that most closely
approximates the power drain and run time of the intended application. For all video
applications this is most definitely the ‘one-hour’ or “C” rate method. which is used by most
professional video battery manufacturers. Unfortunately not every company offering video
batteries uses rates their batteries to the application. They use the rating that the cell
manufacturer uses to rate a single cell for applications drawing 1/5 of the power of a typical
professional video camcorder.
In addition to this numbers game, the relationship between current drain and available capacity is very relevant when comparing batteries of different sizes even if they are properly rated.
The term ‘effective capacity’ refers to this variation of capacity under different current loads.
E ffective Capacity - Contrary to popular belief and simple logic, two 50-watt hour batteries
will deliver less run time than one 100-watt hour battery. This is due to “effective capacity”
which derates the capacity of a battery based on increased power drain. In essence, a 25-watt
camcorder represents a ‘light’ load to a 100-watt hour battery but appears twice as large to a
small 50-watt hour battery. As a result, the 50-watt hour battery may actually deliver only 40
or 50 watt hours while the 100-watt hour battery will provide a full 100 watt hours with the same
load. Thus it may take ten 50-watt hour batteries with up to 9 change disruptions to equal the
run time of four 50-watt hour batteries with only 2 interruptions. In addition, the 10 smaller
batteries will weigh more than the 4 larger batteries. And don’t forget “charge position”. Ten
smaller batteries will require 3 four-position chargers instead of one. In most cases the longest
runtime per battery system is less expensive to purchase and far more economical over time.
Camera/Camcorder Balance - The critical mistake of selecting a battery with insufficient
capacity can almost always be traced to the misguided penchant for a ‘lighter weight’ battery.
In reality, most video professionals agree that good balance is far more critical than a minor
difference in overall weight.
With wide angle and widescreen lenses becoming more sophisticated and heavier, and
camcorders becoming more compact, the overall package is becoming front-heavy on the
cameraman’s shoulder. This front biased weight places a fatiguing strain on the operator’s
right arm and back. In almost all cases the proper 2-hour battery at the rear will perfectly
balance and stabilize the camera, eliminating back and arm fatigue while operating the
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camera for longer periods. A camera with a “heavier” battery, that counters the lens weight,
can be more easily managed, be steadier and feel more comfortable than an unbalanced camera
equipped with a “lighter” battery.
The irony here is that many cameramen create all the insufficient capacity problems outlined
above thinking that they are getting some kind of weight benefit. In reality they trade away
current carrying capability, runtime and camera comfort and stability and in their effort often
increase the number of batteries, and therefore the weight, they carry to a shoot.
Capacity and Voltage - Do not forget the lesson of figure #2 in the Voltage Technical Section.
Using a battery of insufficient voltage can reduce available capacity up to 80%, especially in
cold weather conditions. Access to 100% of the available capacity can be assured only if the
EODV of the battery is above the cut-off voltage of the camera/camcorder.
Capacity
Capacity and package size – simply put there is a big difference in the 65 watt hours of a
large NiCd battery and the 60 watt hours of a small lithium ion pack. Because of the
construction of the cells and the differences in the chemistries, for a given load the lithium ion
battery, constructed of the smaller cells could be working 10 times as hard as the NiCd pack.
While the smaller pack has a tremendous advantage in power per unit of volume or weight,
the larger pack is capable of powering a much larger load – like a camcorder, on-camera light,
monitor and wireless receivers. So instead of requiring separate batteries for these devices –
the battery constructed of the larger cells can handle these loads easily. You wouldn’t specify
a motorcycle engine for a race car – smaller engines work harder and have shorter lives.
Careful consideration of the operating capabilities of the battery with the equipment you want
to power the way you want to use it is key. Size matters, but performance and long service life
are just as key.
Capacity and Charging - When you get to the Charging Technical Section you will learn
that despite everything that has been said here, the charger/battery relationship ultimately
determines whether the battery will run the camcorder for two hours or two minutes.
15
BATTERY CONSTRUCTION
It is quite ironic that in this era of “high tech”, many battery problems, failures, and hazards
are still the result of something so mundane as poor ‘packaging’ techniques. A rechargeable
cell is actually a very fragile device that can be damaged or destroyed by physical forces
typically encountered every day. In the case of lithium ion chemistry, the requisite circuitry
necessary to allow the safe operation of this technology, must be included on a printed circuit
board in each battery. Lacking the properly designed electronics, protective casings and
professional construction techniques, a battery has no hope of surviving in the real world of
professional ENG/EFP. Moreover, improper construction can create a very real and serious risk
(See Safety Hazards Section).
Battery Construction
To assure dependable operation and preclude failures and hazards caused by poor
construction techniques, choose a battery based on the following design guidelines:
1 - The battery should have a very durable case of high impact injection molded material. The
cells inside should be isolated from the case at points of critical stress such as corners. Badly
packaged batteries offer no protection to the cells or critical safety circuits and will transmit
any impact directly to these vital components causing internal cell damage or dangerous
failure of safety circuitry.
2 - Look for solid, unitized construction which distributes and absorbs impact like a crash
helmet. Avoid batteries that are constructed of two halves that are screwed together. Screws
can create stress concentrations that will crack under impact and also prevent impact energy
from being distributed evenly over the entire battery.
3 - Electrical contacts must be low-resistance and preferably gold plated multi-point contact
types. Insertion of the battery into the charger or camcorder should result in significant
‘wiping action’ to maintain a clean and reliable connection. The contacts must also be
recessed significantly to preclude short circuits should the battery accidentally come into
contact with a small metal object. Avoid cables and connectors which will exhibit high
resistance thereby lowerings the output voltage and significantly reducing run time. In
addition, these cable type connectors are very prone to damage and failure in the field.
The importance of a rugged and well designed case has recently gained additional
significance. Some of the latest high capacity cell and new chemistries achieve greater energy
capability by utilizing thinner cell casings and an internal construction which is more fragile.
Without adequate protection, fragile cell constructions often cause more problems than they
solve in the real rigors of a video operation.
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CONSTRUCTION TECHNICAL SECTION
This figure illustrates the basic interior construction of a
rechargeable cell. The basic elements include one positive and
one negative plate that are kept apart by two extremely thin
separators. These plates and separators are wound together
jelly-roll fashion and ‘stuffed’ into a thin walled metal canister.
The negative plate is welded to the bottom of the canister.
After the proper amount of liquid electrolyte has been added,
the positive plate is welded to a top-cap that is then used to
seal the top of the canister. The insulating ring between the
cap and canister also helps create an ‘airtight’ seal. While the
cell is designed to operate as a ‘sealed system’, a safety vent in
the cap will discharge the excessive pressure that could result
from improper charging or discharging practices. The key word in this paragraph is “thin”;
thin separators, thin plates, and thin-walled canister.
Battery Construction
Lithium ion cells have a significant variation in construction. These cells, because of their
potentially volatile nature if abused, have a safety vent which is designed to electrically
disconnect the cell in the event of overpressure. This overpressure can be caused by charger
failure, physical abuse or cell imbalance in the battery. Designed to be only a “last ditch” or
“failsafe” safety mechanism, the safety vent in a lithium ion cell is not designed to be resealable.
If battery and charger are operating properly, the safety vents of the cells in a battery should
never operate. If the vent does open, it is designed to simultaneously disable the cell and thereby
the battery pack. Because the electrolyte in lithium ion chemistry is an organic material it is
highly flammable. The cell (and its safety vent), if operating properly, is theoretically designed
not to allow the escape of this material.
Internal Short Circuits - The canister of any rechargeable cylindrical cell offers very little
protection to the internal components. Firstly, it is so thin you can easily crush the canister
between your thumb and forefinger like a miniature beer can. Secondly, the internal plates
and separator assembly are practically press fit into the canister so that even the slightest
deformation of the canister will cause a corresponding distortion and stress to the plates and
separator. The separator is the only thing keeping the positive and negative plates from
touching and it is so thin that you can see through it like tissue paper. Thinning out plates
and separators is the primary method for putting more active material and thereby more
energy into the same size cell. These two facts account for one of the most plaguing battery
problems: the high impedance internal short circuit.
Accelerated Self Discharge and Imbalanced Batteries - When a battery is tossed onto a
shelf or accidentally knocked against another object, a cell case can be slightly dented, creating a permanent internal pressure point. At this pressure point the two plates are being
squeezed together and eventually the separator begins to break down allowing a small leak of
current to pass from the positive plate to the negative. This phenomenon is sometimes
referred to as ‘accelerated self-discharge’. Depending on the severity of the ‘short’, a cell can
totally discharge itself in a few days or even a few hours. This condition causes several serious
and sometimes perplexing problems.
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In the case of lithium ion cells, a damaged cell will render the entire battery useless – there is
literally no room for error. Because each cell has a nominal voltage of 3.6 volts, a 14.4 volt
pack is constructed of 4 cells. Eliminating one damaged cell reduces the voltage of the pack to
10.8 volts, which is below the operating voltage of a camcorder. Thus the battery is
permanently and irrevocably “dead”.
Battery Construction
Because NiMH and NiCd batteries are constructed of 12 cells of 1.2 volts each (to make a
14.4 volt pack) the battery can still operate a camcorder with one or two cells damaged.
While these cells may be totally depleted, the remaining cells may actually be fully charged.
However, because of its reduced performance and the inability of conventional chargers to
address this conditions, batteries exhibiting this condition will often be discarded (as an offering to the “memory” gods) despite the fact that the battery is still fully operational with the
equipment.
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BATTERY DESIGN FEATURES
The voltage, capacity, and case construction of a battery are critical elements that can be
easily qualified. However, there are many other aspects and features of a battery design that
can have a profound effect on the efficiency and reliability of an ENG/EFP operation. When
selecting a battery system, the following additional points must be considered:
Cell Type and Quality - There are now many different cell types, chemistries and formulations
available from a multitude of cell manufacturers around the world. Relatively few of these
manufacturers produce cells with the quality and performance features which meet the
requirements of professional video. Within this small group of premium cells there are several
different formulations that have specific performance benefits and trade-offs. Factors such as
run-time, overall life, economy, and charger compatibility must be considered. The Cell
Formulation Technical Section below covers some of the more basic aspects of cell selection.
Quality Controls - Research has shown that an
analysis of the first few cycles of a battery can
reveal potential problems that would eventually
prove disruptive in the field. We believe the
computerized 100% full discharge testing
performed on every Anton/Bauer professional
battery is an exemplary form of quality assurance.
This computer print-out, which is shipped with each battery, indicates capacity, voltage
plateau, and includes a complete voltage discharge curve which is the most effective indication of overall cell matching and performance.
Battery Design Features
Internal Battery Construction - While the integrity of the overall battery case is the
paramount construction feature, the quality of the internal assembly is also quite important.
All cells should be strap welded to eliminate high resistance connections. Cell insulating
sleeves should be heavy-duty fiber type instead of thin PVC plastic. PVC plastic insulation can
crack and split due to temperature variation, causing shorting between cells and potential fire
hazards. The design should incorporate printed circuit boards and molded-in wire channels
which eliminates wire flexing, connection fatigue, and pinched wires that can cause short
circuits. An analysis of assembly techniques and components combined with plain common
sense can often indicate which batteries will survive in the field and which are failures or
hazards waiting to happen.
“Universal” Vs. InterActive Batteries - All batteries can be classified into two basic categories:
(1) so-called “universal” replacement type batteries, and (2) Batteries that are an integral part
of an InterActive™ battery/charger system.
The “universal” type usually includes just two electrical contacts and a fixed rate fast charger
output. The InterActive battery is part of a battery/charger system that relies on precise
battery data to facilitate accurate and dependable charging. The battery must therefore have
a network of sensors and circuits in order to monitor the necessary parameters and provide
the data required by the interactive charger. The battery must also include communication
contacts in addition to the two power output contacts. As explained in the charging section,
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only an InterActive battery/charger system should be considered for professional video and
film applications.
Digital Battery - The most advanced InterActive battery is the Anton/Bauer Digital battery
that includes a microprocessor in addition to the other sensors and circuits. These on board
electronics provide the highest level of charge accuracy and convenience while facilitating a
new type of automatic battery management and maintenance system.
Battery Design Features
The Digital battery pioneered a unique feature that has become a standard feature for today’s
cameraman. The microprocessor in the battery includes a “fuel computer” program that
monitors electrical current both into and out of the battery and accurately computes the state
of charge, remaining capacity and remaining runtime at all times. This accurate computation
of available capacity and remaining runtime of the equipment is displayed in a LCD on the
battery. The cameraman knows at a glance the remaining capacity or runtime available from
the battery. In addition to this LCD in the battery, all professional video camera/camcorder
manufacturers include a ‘remaining battery capacity indicator’ or ‘fuel gauge’ in the
viewfinder that couples instantly to a special InterActive contact on all Anton/Bauer Digital
Batteries. This InterActive viewfinder display can be a ‘bar graph’ or digital ‘percent
remaining’ number.
Cameramen have been mislead for years by the unreliability of the meaningless ‘low battery
warnings’ which merely measure battery voltage. This fuel gauge feature, now included as a
standard, without modification to the camera, on virtually all camcorders (and many other
types of equipment) from all manufacturers.
Battery Mounting - The following points should be considered when selecting a battery and
mounting system:
1 - A quick-release mount is preferable to a battery that slides into a box or compartment.
The box concept restricts the equipment to a specific size battery while a quick-release mount
allows the user to use any of a variety of battery types and sizes to match a particular
assignment. Furthermore the quick-release mount allows the equipment to be made much
smaller for transporting by merely removing the battery.
2 - Do not use batteries that have a cable mounted connector. The high resistance of the
small connector can cause voltage reduction problems while the wire and its mating with
both the battery and connector have consistently been identified as the most frequent cause
of battery failure. In addition, these connectors often have no latch or mechanism and
frequently become disconnected inadvertently during operation and charging.
3 - Make sure the power contacts are rated for a minimum of 10 amps and are self cleaning
‘wiping action’ type connectors where a male plug slides into a corresponding female socket.
Avoid ‘touch’ type contacts that are not self cleaning. Also avoid contacts that are riveted.
Lastly avoid the use of any connector that creates a “point”contact. The larger the surface
contact between male and female connection the more reliable the connection will be under
load.
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4 - The battery mount on the camera should include a power socket designed specifically to
power a camera mounted light or other accessory such as wireless receivers. Camera
mounted ‘fill’ lights powered from the camera battery have become necessities for high
quality location video. This power connection should be independently fused, and capable
of handling up to 85 watt loads. In this way, a wide variety of lighting requirements can be
addressed while protecting the camera even if a problem develops with the light. Avoid
lighting outlets on the battery itself. First, these connections require the light or accessory to
be unplugged every time the battery is changed. Second, because a failure of this connection
could disable the battery leaving the operator with no power for the camera.
Battery Design Features
21
CELL FORMULATION
Nickel Cadmium (NiCd)
The continued development of higher energy NiCd formulations, improved manufacturing
techniques keeps this technology in the mainstream of portable power, especially in high
power applications such as power tools and professional video. These improvements have
been dramatic in recent years with capacities improving as much as 50% or more over the
past 5 years. Design requirements driven by power tools and by the alternative transportation
markets have led to a renewed interest by cell manufacturers in NiCd cell design and manufacturing methods. This renewed development stems from the failure of other rechargeable
chemistries, such as NiMH, lithium ion and lead acid to approach the broad range of sizes,
high current capability, low resistance and service life of NiCd.
Cell Formulation
With the advent of worldwide recycling and reclamation programs, any early environmental
concerns regarding the disposal of nickel cadmium cells have been addressed decisively by the
battery industry. Today all types of batteries – lithium ion, nickel metal hydride, NiCd nickel
cadmiuim and sealed lead acid are handled in recycling programs around the world similar to
those recycling glass or cardboard. (for more information see www.rbrc.org for information on
the Rechargeable Battery Rrecycling Corporation, which Anton/Bauer is a member.)
Charge times for NiCd batteries of about 1 hour can be up to 3 times faster than either NiMH
or lithium ion, making NiCd indispensable to a fast paced professional. In the many applications of greater than 40 watt power requirements (such as a camcorder and on-camera light),
NiCd remains the only rechargeable technology which optimizes the factors of cost, reliability,
runtime and service life.
The service life of NiCd batteries is unmatched by any other cell chemistry in video applications. In typical operation, especially in professional use, NiCd chemistry offers as much as
three times the cycle life of any other chemistry.
Within the NiCd family there exists the widest variety of cell sizes and formulation. Since the
differences within NiCd batteries can be significant to their operating characteristics, the following discussion offers an explanation of the three types generally encountered in professional video batteries.
1 - “Sintered/Sintered” - This is the classic premium NiCd cell which has been employed by
most professional video battery manufacturers for more than a decade. This designation refers
to the fact that both the positive and negative plates have been impregnated with active
material using a sintering (baking under pressure) process. This type of construction has
earned a well deserved reputation for ruggedness, long life, and consistent performance
under a wide range of conditions. Developments in sintered/sintered technology have resulted in improved capacity while retaining the other desirable attributes of this type cell which
include heavy duty construction and low internal resistance. This type cell is still the choice for
applications stressing reliability, high power drain, and long life under extreme conditions.
22
2 - “Pressed” or “Pasted” - While this type cell also utilizes a sintered positive plate, the active
material is pressed onto the negative plate. (Japanese cell manufacturers use the term “pasted
negative” while Americans refer to this type cell as a “pressed negative”). This type cell is
typically considered to be of inferior quality relative to a sintered/sintered. Though it exhibits
slightly greater initial capacity for its size, the pressed negative cell never-the-less remains
unpopular for professional video applications. This was due to several serious drawbacks
which included an inability to be effectively fast charged, shorter cycle life (especially when
fast charged), higher internal impedance, and greater susceptibility to internal damage and
shorts.
3 - “High Porosity” - This type cell is based on a very high porosity plate construction that is
sometimes called “sponge metal” or “foamed positive”. Which exposes significantly more
plate material to the electrolyte and thus the battery appears to have the plate area of a
larger cell. Such technology theoretically holds the promise of greater power density for
certain applications. However, this cell construction exhibits all the aforementioned
characteristics of a pressed negative type cell and the associated caveats of susceptibility to
mechanical shock, high drain limitation, and shorter cycle life expressed above apply equally
to this type cell.
Nickel Metal Hydride
Cell Formulation
Advancements in NiMH have improved this technology to offer very high watt hours per unit
of volume. The weight of a nickel metal hydride cell is about the same as a NiCd and the
same number of cells are required to make a battery of a particular voltage. NiMH cells have
the same voltage as their NiCd cousins with the ability to store more energy due primarily to
the highly porous metal hydride electrode.
In practical application, no conventional NiCd charger can handle the stricter charge controls
required by NiMH technology (see CHARGING SECTION below). C-rate charging with TCO,
-ΔV, and/or timed cutoffs are not acceptable methods to terminate charge. NiMH are not
“drop-in replacements” for NiCd cells in any battery application. NiMH cells have a lower
tolerance for high rate charge (excessive heat buildup lowers charge acceptance) and
overcharge (degrades performance and cycle life). In fact, the cutoff methods employed for
NiCd products by conventional chargers will not protect NiMH cells from damage (for
example the -ΔV specification for safe charge cutoff is twice as precise as with NiCd). The only
precision cutoff methodology for NiMH is a dT/Dt (change in temperature over a specified
period of time). This cutoff methodology has been implemented in the computer industry
since the early 90’s (such as the type developed by Anton/Bauer for Apple computer based
on the video InterActive™ Digital battery) and sophisticated processing of temperature
information supplied by the battery. Every Anton/Bauer InterActive charger possesses the
ability to perform the dT/Dt calculations necessary to handle NiMH effectively and safely.
The operating characteristics of NiMH cells have been dramatically improved in recent years.
Early NiMH cells were restricted by limited low temperature performance as well as high
temperature cycle-life limitations. However recent improvements in NiMH chemistry, as well
as the high voltage design of Anton/Bauer HyTRON batteries have virtually eliminated these
concerns. HyTRON 50 batteries were the only power source for an expedition from Death
Valley to the top of Mount Whitney experiencing operation temperatures ranging from
23
around 100°F (38°C) to 15°F (-10°C). The cells used in the HyTRON 120 battery were
specifically designed for high current applications such as electric bicycles and power tools.
Unlike any other chemistry new to professional video, HyTRON batteries do not require the
purchase of a new charger to take advantage of the battery’s performance. Any Anton/Bauer
InterActive charger with full communication capability can be upgraded with a new software
chip to safely and reliably charge HyTRON.
Lithium Ion
Cell Formulation
Of all rechargeable chemistries, theoretically, lithium ion offers the future promise of smaller
lighter batteries to match up with small low power equipment. For over 40 years cell
manufacturers have been attempting to harness the energy potential of exotic metals, such as
lithium, into a reliable and safe rechargeable technology. Every early attempt was disastrous,
leading to catastrophic and costly failures of batteries and equipment. Lithium ion chemistry,
which does not use lithium metal in its pure form, has been more successful in recent years in
small two-cell batteries for low power equipment. Unfortunately, several lithium ion product
recalls have perpetuated safety concerns and design considerations.
The major advantage of lithium based cell chemistry is the voltage of the cell. Instead of
being a nominal 1.2 volts per cell, lithium based chemistry has a nominal 3.6 volts. This
voltage advantage (the capacity of any particular size lithium ion cell is typically about the
same as a nickel based chemistry) allows a 14.4 volt nominal battery to be made with only
four cells in series instead of 12 cells for the nickel based chemistries. However, since the
lithium ion cells are currently only manufactured in the small sizes designed for cell phones
and computers, to obtain the same capacity in a similar volume package, the cells must be
paralleled to obtain requisite capacity. Therefore, to obtain capacities equivalent to other
chemistries as many as 12 cells (or more depending on the size of the cells) must be used.
The resultant volume and capacity of the lithium ion battery is equivalent to batteries made
with the other chemistries, while its weight will be about 20% less.
The single major disadvantage of this chemistry is made obvious by the absolute requirement
for on-board “protection” electronics to prevent overcharge (which results in catastrophic
failure) or over-discharge (which renders the battery useless). These electronics must monitor
each and every cell in the battery to prevent any over charge or discharge of any cell. This
should be a relatively simple process for a single cell (3.6 volt battery) but gets increasingly
more complex and subject to the tolerances of the cells and the electronics. This is especially
the case as the cells are paralleled to obtain higher capacities.
Lithium ion chemistry is being employed, primarily in small size (AAA or small rectangular
sizes) 2 cell configurations in the cellular industry and in the computer industries, where primary considerations are weight and size. Moreover, the devices they are designed to power
(computers and telephones) have additional battery monitoring programs which can improve
performance and reliability.
24
Lithium ion cells can retain their charge for a somewhat longer time than other technologies.
However, lithium ion batteries stored for any time irreversibly lose capacity (see discussion of
self discharge and battery storage below).
Another drawback to lithium ion technology as a professional battery is its inability to address
high rate discharge. The internal resistance of lithium ion cells used in professional video
batteries is up to 10 times that of similar cell sizes in NiCd and NiMH. In fact, the battery itself
must be fitted with electronics to limit the amount of current that can be drawn from the
battery. While this is of little consequence in a “closed system” like a cell phone where the
battery is matched exclusively to one device for its lifetime, in a video operation a battery
can – and will - be used on a variety of equipment
When trying to operate a camera and on-camera light for example, the protection circuitry
(required to protect the cells from over-current) can often shut the battery down as the
increased load pulls the battery voltage down even momentarily. Some cameras attempt to
get around this by limiting the current which can be drawn from its accessory connector for
the light. A voltage regulator in the camera limits the current draw of the light rendering it
virtually useless for high wattage bulbs, like those used for daylight fill. Since the camcorder
and light configuration is the most popular and economical operating arrangement in
professional video, this limitation is significant for this chemistry.
Cell Formulation
Unquestionably lithium ion differs dramatically from any other rechargeable technology due
to the nature of its electrolyte. Much of the technical discussion in the battery industry
regarding lithium ion has to do with some well founded concerns of reliability and safety.
The electrolyte (the liquid medium which allows the transfer of electrons between the positive
to the negative plates) and the volatility of lithium metal (which can be formed under certain
abuse situations) are the characteristics which a great deal of the R&D efforts by the cell
manufacturers are seeking to improve. Currently, most lithium ion cells in all applications and
all those employed in professional video batteries use an organic electrolyte which is highly
flammable. Unlike other chemistries, which uses an aqueous (water based) potassium hydroxide electrolyte, a lithium ion cell itself can support a fire.
The battery industry is actively pursuing development efforts to address this issue – such as
polymer based electrolytye. However this technology has even less current carrying capability
and as yet is not capable of producing a professional video battery to meet the demands of
today’s video equipment.
Since its first introduction in the early 1990’s there have been numerous lithium ion battery
catastrophic failure “events” primarily in the notebook computer and cell phone markets. In
every market where lithium ion appears, including professional video, there have been
associated product recalls as a result of serious safety concerns.
When choosing a lithium ion battery, make certain that the battery is constructed with the
requisite safeguards and is supplied by a reputable and experienced manufacturer. Avoid look
alike batteries that may not have the same safeguards in design and manufacture as the
original manufacturer’s products. Never charge a lithium ion battery on any charger other
than the charger on which the battery was designed to be used.
25
Lead Acid or Gel Cells
This cell chemistry has no viable application to professional or consumer video today. The
only allure of lead acid/gel cell batteries was their initial low cost. In reality these cells were
more expensive than NiCd due to a significantly shorter cycle life and unreliable performance.
With a high internal impedance, these type cells also exhibited significantly reduced ‘effective
capacity’ in professional video applications. Relative to a comparable NiCd battery, lead
acid/gel cell types are bigger, heavier, more costly, have less than 1/4 the cycle life and are
irreparably damaged if left in the discharged state for extended periods.
Silver Zinc
These type cells have been popular in limited circles since the advent of ENG/EFP. At that
time, silver zinc had a power density 3 times that of NiCd and several television networks
opted to build an ENG operation around this technology. Cameramen loved the ‘shoot-allday-on-one-battery’ aspect which eliminated battery interruptions and the need to carry extra
batteries. However, silver zinc is extremely unforgiving due to operating limitations and its list
of maintenance procedures.
Cell Formulation
While it remains widely used in military applications, silver zinc is no longer considered a
viable alternative for professional video.
26
CHARGING
Once a professional battery of the correct voltage and capacity for a particular application
has been selected, the success or failure of your video operation will depend almost entirely on
the charging system. Poor and erratic performance is primarily due to a basic characteristic of
rechargeable batteries known as “charge acceptance”. Simply stated, a battery actually
rejects or accepts any or all the current from a charger depending on a multitude of
prevailing conditions. Contrary to the outdated popular concept, a battery is not like the fuel
tank in your car that merely has to be ‘filled’ with a specific quantity of fuel. A battery is more
organic and can not be ‘filled’ with charge current any more than a flower can be ‘filled’
with water. In order to achieve optimum capacity a battery must be ‘fed’ charge current in
a precise manner according to a multitude of parameters and conditions. All conventional
chargers ignore these factors and merely deliver a fixed and steady flow of current, reducing
battery performance to a mere game of chance. It is not uncommon for a charger to
indicate that a battery has been given a full charge and is ‘ready’ to use when in fact the
battery has ‘accepted’ less than half the charge current and thus contains less than half its
potential capacity.
Charging
It is now acknowledged that the charging process must consider all the parameters and
conditions that affect charge acceptance in order to properly charge a battery and assure
optimum performance. This is exactly the basis of the latest innovation in battery technology:
InterActive battery/charger systems. The key to this technology is designing the battery and
charger together as a complete system. During charging, the battery and charger “talk” to
each other. The battery is designed with a network of electronic sensors that monitor vital
charging parameters while a program module contains critical data such as cell formulation,
capacity, and voltage. All this data is fed to the charger microprocessor which then creates the
optimum charge regime for that battery under the actual prevailing conditions. In essence the
battery is controlling the charge process by telling the charger who it is and how it wants to
be fed today. This technology brings rechargeable batteries from the dark ages into the space
ages with consistent and dependable high performance while eliminating the fire and
hydrogen gas explosion hazards that have always existed with conventional chargers.
This is the only rule of charging you need to know: select an InterActive battery/charger
system for dependable high performance and safe trouble free operation. With the
development and introduction of this highly reliable system technology, it would be a
travesty to base a professional video operation on anything else. (The Technical Section
covers the specific benefits and technical features of this system as well as the problems of
conventional charging.)
NiMH and lithium ion batteries can not be charged on conventional NiCd chargers, or more
to the point, these batteries can be destroyed and create a hazard to the operator if such is
attempted. An InterActive charger includes its programming on a replaceable chip within the
charger. As each cell improvement or new cell technology is introduced, the corresponding
charge regimes may be programmed into an updated chip that is simply inserted into the
charger in place of the old one. The updated charger could will then identify and properly
charge the new type batteries as well as all the older types simultaneously. With a system that
anticipates inevitable technology changes, a gradual and economical transition to advanced
new chemistries is possible now and in the future.
27
CHARGING TECHNICAL SECTION
It is the charging system, or more precisely the battery/charger interaction, that will ultimately
make or break a portable video operation. Assuming a professionally constructed battery of
correct voltage and capacity has been selected for an application, all remaining problems of
poor or erratic performance can always be traced to improper charging practices or a charger
with insufficient control and safety circuits.
Charging
Charging different chemistries used in professional video requires the employment of radically
different charging routines. Each chemistry – NiMH, NiCd, lithium ion – require different
methodologies based on the characteristics of the chemistry. The three characteristics
common to all cell chemistries which indicate charge completion are temperature, voltage
and internal cell pressure. Each of these factors are equally important. As a cell nears full
charge, the voltage of the cell, its temperature and pressure all will rise. The art in charging a cell
is to obtain the most charge without the increase in these parameters exceeding safe limits
specified by the design of the cell. Exceeding the limits of any of these factors, depending on
the chemistry, can lead to unreliability, shortened service life or in some cases catastrophic
failure of the cell, including explosion and/or fire.
Unfortunately, the best indicator of charge completion, internal cell pressure, is virtually
impossible to monitor. The rise in gas pressure internal to the cell cannot be monitored
economically, especially in a multi-cell pack – as it would require the equivalent of pressure
gauges on every cell. It is, however, the internal pressure of the cell which, when exceeded,
can cause the destruction of the cell. Since the buildup of pressure cannot be effectively
monitored, the precise control and monitoring of the other two characteristics is paramount
in proper charger design.
All cells used in professional video are vented. That is, they possess as part of their mechanical
designs, safety mechanisms – in the form of vents - to release gas pressure built up during any
charging which exceeds the parameters of the cell design.
These safety mechanisms are vents which allow the buildup of gases created during
overcharge to be released from the cell. In the case of NiMH and NiCd cells the vents are
resealable. This means that the nickel based technologies not only can withstand some degree
of overcharge, but if the internal pressure limits are exceeded, the cell can expel small
amounts of any excess gas. The expelling of the gas will typically carry with it some of the
liquid electrolyte in the cell. This electrolyte is a relatively benign material in nickel based
rechargeable cells (typically potassium hydroxide in a water based solution). The loss of too
much electrolyte due to venting will ultimately prohibit the ability of the cell to generate an
electro-chemical reaction, thereby rendering it useless.
In the case of lithium ion chemistry, the vent is designed to be a one time device. That is,
since the lithium ion cell is incapable of absorbing the effects of any overcharge, the vent is
designed to electrically disconnect the cell – much in the same way as a fuse breaks an
electrical circuit. The cells are designed in this fashion to prevent the escape of any liquid
electrolyte. Since the electrolyte used in lithium ion cells is an organic material (another
liquid organic material, by way of reference is gasoline) with an extremely low flash point
28
(or temperature at which the material will ignite), the release of any electrolyte could be
catastrophic to the battery and to personnel. It is for this reason that a lithium ion battery
requires the use of electronic circuits in the battery design to monitor other battery
parameters to prevent any build up of gases from overcharge.
The next best indicator of full charge is temperature. The temperature of a cell will typically
rise as it reaches end-of-charge due to the cell’s increased internal resistance and its
corresponding inability to absorb the energy being delivered by the charger. The two ways
which temperature can be monitored is by an absolute change (TCO) and a relative change
(ΔTCO). Both NiMH and NiCd cells can be most effectively charged using a temperature
method. By monitoring the temperature of the cell, the full charge state can be determined
before any build up of gasses occurs. This method is the most effective when dealing with a
multi-cell pack – as all professional video batteries are constructed.
Charging
Lastly, the most conventional and basic method of approximating the full charge of a cell is by
monitoring its voltage. Charging to a particular voltage (absolute voltage) or charging to a
calculated inflection point (-ΔV or peak voltage) are typical methods of using voltage to
determine full charge. Unfortunately, since professional video batteries are made up of from 4
(lithium ion) to 10-12 (NiMH, NiCd) cells, the accurate monitoring of each individual cell in a
battery pack is almost impossible (see voltage cutoff discussion below). The charger,
however, is only capable of “seeing” the combined voltage of the entire series pack. Because
the voltage change of any given cell can be disguised by an inverse voltage differential of
another cell or group of cells in a series pack, protecting the individual cell requires the use of
precision monitoring circuits connected to each cell. Using only a voltage cutoff can lead to
the overcharging of one or more cells in a series pack, one factor causing so-called “memory”
in nickel based chemistries.
In the case of lithium ion, the required individual cell voltage monitoring must be done within
the battery pack itself. The charger is able to determine the voltage of only the entire pack.
These on board battery electronics should signal to the charger the attainment of the end-ofcharge voltage of any individual cell before any dangerous overcharge can occur. These
essential electronics are built into the battery and must be protected from the same shock,
vibration and environmental conditions to which the battery is subjected in field use.
NiCd and NiMH batteries are typically charged with a constant current methodology, meaning
that the charger will deliver a constant amount of current to the battery regardless of its voltage. In charging this way the current delivered to the battery can also be measured and a failsafe time termination can also be employed.
Lithium ion chemistry must be charged with a constant voltage architecture (constant current
may be applied early to expedite the charge process but a constant voltage methodology is
required as the cell becomes mostly charged). This means that the voltage applied to the
cell(s) is constant and the current applied will be reduced as the voltage of the cell(s)
increases. This charging method is similar to the method used to charge lead acid batteries.
Only the voltage of the cell(s) can be used to determine full charge and must be done so with
extreme precision, as lithium ion chemistry is incapable of absorbing any overcharge safely as
discussed previously.
29
The following discussions address the most commonly recognized methods of charging, as
well as the mis-application of these methods which cause premature battery failures.
Charging
SLOW CHARGING
Every NiCd cell used in the video industry has an inherent ability to accept a certain amount
of overcharge current indefinitely. NiMH has a limited tolerance and lithium ion has an
absolute zero tolerance for overcharge. In the case of NiCd, the tolerance to overcharge is
largely due to the typical cell construction with a negative plate that has slightly more area
than the positive plate. During charging, virtually all the charge energy is being stored in the
cell by converting the chemical elements of the internal plate compounds. The cell is
essentially fully charged when all the positive plate material has been converted. If the charge
current continues past this point, it can not be absorbed by chemical conversion and instead
produces oxygen gas at the anode. This oxygen is contained in the cell where it eventually
finds its way to the unused portion of the larger negative plate where it is absorbed. In the
process of absorbing oxygen, heat is created and thus the overcharge current is essentially
dissipated as heat. The cell is designed to dissipate a certain amount of overcharge current in
this manner indefinitely with no immediate adverse affects. If the overcharge current were
greater than this ‘C/10’ rate, the cell would begin to produce oxygen at a rate much faster
than it can absorb. The internal pressure would rise dramatically until the safety vent opened
spewing forth gas and electrolyte. This ability to absorb oxygen has its definite limit which is
usually at a current that is one tenth the ampere hour rating of the cell (C/10 rate). Thus a 5
amp hour NiCd cell can typically absorb up to 0.5 amps or 500 ma of overcharge current
continuously with no immediate adverse effects.
This continuous ability to dissipate an overcharge current of up to ‘C/10’ is the precise basis
and definition of a “slow” or “overnight” charger. The term “trickle charge” is also used to
describe charge rates of ‘C/10’ or slightly less. Such chargers are incredibly simple and in
many cases consist of little more than a transformer and a diode in a small black box. The
‘C/10’ constant current will typically charge the appropriate battery in 16 to 20 hours and
when the battery is fully charged there is allegedly no problem as the battery will happily
dissipate the continuing charge current indefinitely. At first glance the ‘slow’ or ‘overnight’
charger seems foolproof, economical, safe, and dependable.
Contrary to its deceptively simple concept, the slow charger is an outdated concept and
should always be avoided for professional video applications for several important reasons:
1 - TIME - Slow charging is too slow for professional applications. The 16-20 hours necessary
for a complete slow charge is totally unacceptable in a professional operation.
2 - CELL FORMULATIONS - Modern cell chemistries have an optimum charge acceptance at
the one hour or ‘C’ or 1It rate. When charged at the slow rate, they can exhibit reduced
capacity with each charge cycle.
3 - HEAT AGING - The vital plate separators and cap seal of a cell deteriorate with age. As a
matter of fact, separator failure and the resulting benign internal short circuit is one of the
more common forms of battery end-of-life failure. Elevated temperatures will accelerate the
deterioration of any organic material and batteries are no exception.
30
Unfortunately, the slow charging process dissipates the continuing excess charge current as
heat.
4 - RESTRICTED APPLICATION - Because of its inherent simplicity and constant current
output, a slow charger must be dedicated to one specific voltage and capacity battery.
A slow charger can be totally ineffective if connected to a battery with a greater rated
capacity or slightly higher voltage than that for which it was designed.
A slow charger should never be connected to a lithium ion or NiMH battery.
“FAST” CHARGING
Virtually all professional chargers are high rate chargers capable of delivering a fully charged
battery within 8 hours and often within one hour. “Fast” charging is used to define a
one-hour-to-cutoff charger, however with the advent of longer requisite charge times of
NiMH and lithium ion, “fast” chargers are typically categorized as any charger that will
deliver a complete charge routine on a battery in under 8 hours.
CHARGE TERMINATION
Charging
In order to comprehend the criticality of any ‘charge termination’ procedure, consider that
the popular one hour fast charge routine for a NiCd battery uses a charge current that is ten
times greater than the ‘C/10’ rate. Thus when the cell reaches full charge it will begin to
produce oxygen gas at a rate 10 times greater than its maximum absorption capability
resulting in a rapid (and potentially catastrophic) build-up of pressure and temperature.
The charge termination or ‘cut-off’ is the most critical element of any battery charger, and
it is the inability of unsophisticated chargers to dependably execute this function that is
responsible for the poor performance, poor service life and sometimes hazardous
malfunctions of today’s video batteries of all chemistries.
Generally, all modern cell formulations ‘like’ to be fast charged (at rates approaching the “C”
or one hour rate) and will deliver optimum performance and charge acceptance when fed a
fast charge rate under proper conditions. However, this situation is reminiscent of the old tale
about the man who fell off the roof of a 20 story building and was not injured from the fall.
However, the sudden stop at the pavement killed him. Likewise, the problem is not the high
current charge rate, but rather the failure to reliably terminate this high rate of current once
the cell is fully charged.
Accurate and dependable recognition of the full charge condition of a battery under all
conditions is extremely difficult. As discussed previously, the only cut-off method for a lithium
ion cell is the attainment of an absolute and precise voltage, which is monitored in the battery
and must be communicated to the charger. NiMH and NiCd cells can be charged using one
or more of the following termination techniques:
VOLTAGE CUT-OFF [VCO] - This is the most popular method of fast charge termination for
NiCd cells. It is the only method that can be used with conventional two contact (+ and only) batteries. As can be seen from figure 3, the voltage of a NiCd cell steadily rises during
31
Charging
the charge process. Upon reaching full charge, the cell begins to generate and reabsorb
oxygen gas as previously described which causes the voltage to drop. In its best form, a VCO
charger uses a microprocessor circuit to monitor the charge voltage and terminate the fast
charge current when this reduction in voltage is sensed. Such chargers are also called -ΔV
(“minus delta vee”) types because of this process. In addition, the microprocessor can also
monitor and respond to other relevant characteristics of the charge voltage, which is referred
to as ‘voltage algorithms’. All these methods that rely on the charge voltage for fast charge
termination are generically VCO type chargers.
Looking at fig 3, the voltage profile, and in
particular its -ΔV aspect, appears to be a
reliable and effective basis for determining
the full charge of a NiCd or NiMH battery.
Actually, if video batteries consisted of one
cell and were always charged under
controlled conditions, this method would
work just fine. Unfortunately, every cell
manufacturer states that the VCO method,
and the -ΔV type in particular, becomes
progressively problematical and unreliable as
the number of cells in the battery increases.
All professional video batteries (except
lithium ion) consist of 10 to 12 cells in series
and thus the problems associated with this type charger should have been anticipated
and expected. The problems with this method are primarily related to temperature and
cell imbalances.
Figure 3
The pronounced rise and then dip in voltage (-ΔV) of figure 3 curve A is based on an
optimized charge rate at room temperature. If the charge rate or the temperature deviates
from these optimum values, the magnitude of the -ΔV dip may be reduced dramatically
(figure 3 curve B) causing it to become unrecognizable to the charger termination circuit.
Thus termination will not be properly executed which will overcharge the battery and create a
fire hazard. This problem often occurs with warm or hot batteries but is particularly acute with
cold batteries.
The -ΔV charger can rarely recognize a cold battery, resulting in one of two very undesirable
conditions. The initial high impedance of a cold battery may create an immediate rise and
drop in voltage when charging begins which prematurely triggers the “Full Charge” cut-off.
This is why a battery from one of these chargers can sometimes have a “READY” indication
and yet remain uncharged. More typically, the charger does not receive a false trigger and
delivers the full fast charge current to the cold battery as if it were at room temperature. Cell
manufacturers clearly warn that this is the most dangerous thing you can do to a NiCd
battery. A cold (40°F or less) NiCd can not accept the full fast charge current and will
generate hydrogen gas under these circumstances. When such a battery is removed from the
charger or placed on a camcorder a spark can ignite the hydrogen gas causing the battery to
explode. (See Safety Section)
32
The -ΔV charger can not recognize or cope with cell imbalances either. The cells used in
premium batteries are usually matched for capacity before assembly. At Anton/Bauer every
professional battery is 100% computer tested for performance and cell balance with the
computer print-out shipped with each battery. Nevertheless, the 10 or more cells within a
video battery will eventually develop slight differences in capacity due to a multiplicity of
factors including unequal rates of self discharge. As Murphy would predict, the probability
that 10 to 12 cells will reach full charge at the same instant is virtually nil. As one cell is
increasing in voltage toward the end of charge, another cell is decreasing in voltage, etc., etc.,
etc. Because the charger can only read the sum voltage of all these cells in series, the cells
with rising voltages cancel out the reduction in voltage of those cells that have reached full
charge. As a result the charger ‘sees’ a relatively flat voltage curve and misses the charge termination point. This is why the cell manufacturers are wary of using the -ΔV technique in such
multi-cell applications. Based on this same syndrome, these type chargers can not cope with
batteries that have “memory” or imbalances caused by high impedance shorts. Such batteries
will either be destroyed, damaged, or result in a partial charge.
(See Memory in the Problem Appendix)
In addition to the hazards, it is clear from the forgoing why batteries charged on these type
chargers have been notoriously unreliable. Depending on temperature, cell matching, and
many other factors, the battery may receive a reasonably full charge one day and a mere
fraction of a charge on the next.
Charging
TEMPERATURE CUT-OFF [TCO] - Upon reaching full charge, the continued charge current
will begin to create heat inside the cell due to the oxygen absorption process. The subsequent
rise in temperature in cells designed for this cut-off method is a very definite and reliable
indication that the fully charged condition has been achieved. When properly monitored and
analyzed this rise in temperature can be a very effective and dependable basis for a fast
charge termination system. A TCO system must include the appropriate temperature sensors
in the battery and an additional connection between battery and charger for the transmission
of temperature data.
In addition to being an effective means of fast charge termination, temperature information
can be extremely vital to many other charger functions. The relevance and accuracy of
battery voltage data during charging is significantly improved when coupled with cell
temperature information. Likewise, the charge acceptance factor that greatly influences
battery performance is also very temperature dependent. The microprocessor of an
InterActive battery/charger system uses the critical cell temperature along with other vital
data to optimize performance and life as well as eliminate the safety hazards of cold
temperature charging.
DELTA TEMPERATURE CUT-OFF [DELTA TCO (dt/Dt)] - The most advanced temperature
type cutoff method is employed in the Anton/Bauer Digital InterActive battery. The Digital
battery contains special temperature sensors which convey real time temperature information
to the charger’s microprocessor allowing the charger to analyze the rate of temperature
change of the cells in the battery pack. This analysis is then used to determine a precise fast
charge cut-off point which is more accurate than either VCO or standard TCO methods.
This cut-off method is essential for safe charging of NiMH (Nickel metal hydride) cells.
A temperature compensated ΔT/Δt is a proprietary standard feature of all Anton/Bauer Digital
33
InterActive batteries and chargers eliminating many of the variables to this type of cutoff that
temperature extremes can introduce.
DIGITAL OR FULL BATTERY CUT-OFF [FUL] - Another feature only available with the
Anton/Bauer Digital InterActive battery and chargers is the FUL cutoff. Due to the InterActive
technology, an Anton/Bauer InterActive battery can communicate it’s own state of charge to
the microprocessor in the charger. Therefore, when a battery reading 100% in it’s display is
placed on the charger, no charge current is needed to bring that battery to one of the
aforementioned cutoff methods. The battery merely tells the charger to enter the proprietary
Lifesaver mode to keep it at the 100% charged level without adding any additional heat to
the battery, therefore prolonging the life of the cells.
Charging
COMPUTATION (or CAPACITY) CUT-OFF [CCO] - The CCO or Computation method of fast
charge termination is a very dependable complement to either the TCO or the VCO systems.
This pre-determined charge profile is established prior to the start of the charge cycle by the
charger’s microprocessor during the battery evaluation phase. By recognizing the battery’s cell
formulation, temperature, rated capacity and number of cells, the InterActive charger’s microprocessor will select a fail-safe maximum charge profile from its database. The charger continuously monitors the charging process against the battery’s maximum charge profile and will
terminate charge automatically if this profile is exceeded.
An explanation of these five termination methods usually prompts the question: “Which one
is best”? And the answer begins with “none of them”. Each method has its strong points and
a specific range over which it is effective, however no one of them are totally safe and
dependable over the full range of conditions that are normally encountered in the professional
film and video industries.
Voltage Cut Off systems, including microprocessor ‘voltage algorithm’ types, are reasonably
effective under ideal conditions but can be extremely unreliable and hazardous if the battery is
cold or imbalanced. The TCO techniques as exemplified by the Anton/Bauer ACS and Digital
InterActive battery systems are extremely effective and are the only safe methods to charge
cold or imbalanced batteries. DT/dt is the only safe and reliable method of terminating charge
in a NiMH battery. The CCO method is a safe and reliable ‘back-up’ system and is effective
under a wide range of conditions, but because it is a ‘computation’ method it lacks the
accuracy requisite for use as a primary cut-off method.
The final answer to the question of which charge termination system is best is:
“all of them together operating simultaneously and independently”.
34
While all conventional chargers employ only one charge termination method, Anton/Bauer
InterActive Microprocessor chargers when used with Anton/Bauer InterActive batteries include
all five types of termination systems which operate at all times. Every Anton/Bauerbattery
includes a complex network of sensors and logic circuits that provide the charger microprocessor with the critical temperature and cell data to facilitate an accurate TCO, Delta TCO,
temperature correlated VCO, FUL or CCO cut-off. The charger monitors all these systems
simultaneously and will accurately terminate the fast charge when any one of these systems
recognizes the full charge state. This fail-safe multi-redundant technique utilizes the strengths
of all these methods while it precludes the inherent weaknesses of any one system. This is the
only system that is safe and effective over the entire range of possible conditions.
CHARGE ACCEPTANCE
As mentioned above, a battery is not a “fuel tank” but rather an organic system that will
efficiently store energy by an internal chemical transformation when fed electric current
(charge rate) in a precise manner and under specific conditions. When these specified charge
rates and conditions are not met, the internal chemical transformations do not proceed in
their normal manner. Under certain conditions the normal chemical transformation will cease
altogether and all the charge current will be diverted into secondary reactions that result in
no energy being stored at all. These secondary reactions include the formation of explosive
gas as well as destructive heat.
It is ludicrous to expect reliability from a charger that just throws out a fixed electric current
without any regard to the critical conditions and parameters that affect the chemical
transformation. Yet virtually all conventional chargers do just that. Charging a battery with
one of these conventional non-interactive chargers is nothing more than a game of chance.
Among the major factors affecting ‘charge acceptance’ (the ability of a battery to store the
energy delivered by the charger) are temperature, cell formulation, and the rated capacity
(size) of the cell. The dire consequence of a charger ignoring these factors can be deduced
by analyzing just one element of the complex charge routine: average fast charge current.
Consider the following facts taken directly from cell manufacturers’ specifications:
Charging
1 - For a given cell, the fast charge rate must be adjusted by a factor of over 1,000 %
according to prevailing temperature in order to assure optimum charge acceptance and
remove the danger of explosion.
2 - Given a particular size cell, the fast charge rate must be adjusted by a factor of over 500%
according to chemical formulation and internal structure.
3 - Fast charge current for a particular cell formulation and temperature is directly
proportional to cell size or rated capacity. Since professional video batteries utilize cells
typically in the range of 2 AH to 8 AH, this represents a corresponding variation in charge
current of another 400%.
From these three specifications it should be clear that based upon the size, formulation, and
temperature of the cells, the safe and optimum charge current would have to be adjustable
over a range of 200 to 1 or 2,000 %. This means that a conventional charger with a single
fixed fast charge rate can be delivering up to 200 times too much or too little current to a
battery according to the safety and performance specifications of the cell manufacturer.
INTERACTIVE CHARGE TECHNOLOGY
The basis of InterActive charge technology is very logical and simple: each battery actually
contributes to its own charge process according to its size, chemical formulation, temperature
and all the other parameters and conditions that affect charge acceptance in order to optimize performance, safety, and overall life. The battery of an InterActive battery/charger system
features a network of sensors and logic circuits that can generate all the vital data necessary to
create an optimized charge routine. Through a special communication link, the InterActive
35
charger responds to this data by delivering a charge profile that perfectly matches the cell
manufacturer’s specifications under the prevailing conditions. All elements of chance and the
risk of uncharged batteries, fire, and explosion are removed.
In addition to dependable performance, safety, and prolonged life, this InterActive technology
is also the basis for a new concept in battery system management. Batteries have always
represented an inordinately large percentage of video maintenance time. By comparison,
modern cameras and recorders require little attention and a stock of fresh video tape is easy
to maintain. Only the battery is an unknown consumable that can cause unpredictable
disruptions when they fail. How do you keep track of the age, recent performance, and use
pattern of a battery in order to identify a potential problem before it becomes a failure in
the field?
Charging
The high level of data available from the battery and microprocessor charger of an InterActive
system can facilitate a sophisticated and automatic maintenance program. InterActive chargers
built-in diagnostic units can automatically test batteries for capacity, voltage profile, and all
other major parameters. Through LCD or attached printer, these sophisticated units can
automatically identify battery anomalies before they cause disruption in the field.
36
BATTERY LIFE
The overall life expectancy of a rechargeable battery is greatly influenced by a myriad of
factors which have been frequently responsible for reducing the life of a battery to less than
30% of its theoretical maximum. There are many video professionals that accept the fact that
a battery appears dead after only 6 months or a year. Most of the factors affecting life have
been addressed throughout this handbook under the associated headings. The following is a
compendium of the major factors influencing battery life with recommendations for
optimizing each.
Heat- Batteries should not be exposed to elevated temperatures. Heat greatly accelerates the
aging process and can reduce battery life by more than 80%. In the case of lithium ion (and
to a lesser extent NiMH) the effect of storage in elevated temperatures can worsen a relatively
new phenomena of “unrecoverable storage capacity”. This characteristic of the so-called
“new” chemistries defines a condition in which the storage of these batteries, whether
charged or discharged, leads to a loss of capacity which can never be regained. Unlike NiCd
cells, which have very good storage or shelf life characteristics, the chemical construction of
these batteries will degrade much faster over time. This degradation is accelerated under high
temperature (40°C and greater) storage conditions. The “use it or lose it” properties of NiMH
and lithium ion chemistries are exacerbated by any long term (30 days or more) storage,
particularly at elevated temperatures.
Battery Life
Whenever possible keep batteries at room temperatures. In extremely hot climates, keep
batteries out of direct sunlight where possible and return batteries to an air conditioned
environment at the earliest practical opportunity. Avoid leaving batteries for extended periods
in an enclosed van or the trunk of a car. A simple styrofoam cooler can help insulate batteries
in extreme temperatures. Common sense can easily predict the many other elevated
temperature situations that should be avoided. In short don’t keep your batteries anywhere
you would not store your tapes or your camera.
During storage for periods greater than a few weeks, batteries should be wrapped in a sealed
plastic bag and placed in a refrigerator. Before being returned to service, the batteries should
be allowed to achieve room temperature before being removed from the plastic bag. Once at
room temperature, the batteries should be charged on an InterActive charger in order to
equalize and compensate any minor self- discharge. Do not use a conventional charger which
has no means for addressing imbalances. Especially in the case of NiMH and lithium ion
chemistry, it may take several charge and discharge cycles following storage for the battery to
return to its optimum capacity.
A charger can often cause the worst elevated temperature environment for the battery.
Improper charge termination and a trickle charge can create extremely high temperatures
which are maintained indefinitely while the battery is on the charger. An InterActive
battery/charger system with accurate temperature sensors and the Lifesaver maintenance
mode will prevent this common form of heat damage. If you are not using an InterActive
battery/charger system, feel the temperature of a battery that has been on the your charger
for about 20 hours or longer. If it is warm or hot to the touch, it is being prematurely aged by
a trickle charge. (If it is at room temperature, it probably is receiving no maintenance charge
37
and will thus self-discharge probably limit the performance of the battery despite the charger’s
“full” indication).
Charging - The charging process has a great influence on battery life. For maximum life every
battery requires a specific charge profile for a given set of conditions. Any deviation from this
optimum profile will have an adverse affect on battery life. As an example, two identical
batteries, charged with different chargers, provided similar performance during the
operational life of the batteries. However one battery delivered twice the number of cycles
and twice the length of service of the other due the differences in the charge routines. In
extreme cases, an improper charge regime can destroy a battery and create a hazard.
As previously explained, only an InterActive battery/charger system has the ability to
identify and create the proper charge profile required for maximum life and performance.
The following guidelines will help prevent extensive life reduction.
Battery Life
a) Do not connect a battery to a charger unless both the battery and charger are from the
same manufacturer. While a charger may appear to be correctly charging a battery, an
improper charge rate or charge termination profile can adversely affect life in addition to
impairing performance and creating a hazard. The use of different cell chemistries, often
disguised by a familiar form factor and connection format, offers a tremendous chance for
serious incompatibility and dangerous operation.
b) Avoid so-called “equivalent” replacement batteries or “re-built” batteries. Remember both
the battery and the charger are responsible for performance. While such replacements or
re-builds may ‘look’ identical to the original, the internal cells typically differ from the originals
for which the charge regime was optimized. Unfortunately such life reducing incompatibility
does not show up until the battery dies in a fraction of the expected time. This and other
internal differences that reduce performance can as well as create a serious safety risk.
c) Do not use slow chargers as a primary means of recharging and avoid chargers that utilize
a continuous trickle charge as a “maintenance” charge.
d) Maintain adequate air circulation space between batteries and around charger. Make sure
the charger is on a hard surface and not on a rug or carpet.
e) Do not routinely use so-called ‘dischargers’ or ‘conditioners’ before recharging. (See
‘Discharge-Before-Charge Section’ in Problem Appendix)
Discharge Rates - The life of a battery can be significantly affected by the relationship
between the size of the battery (rated capacity and cell size) and the rate of discharge.
For a given size and type battery, higher discharge currents will reduce overall life expectancy
while lower discharge currents will enhance battery life. (This is primarily due to internal
impedance and heat).
As this rule applies to video, the life expectancy of a battery will not be adversely affected
by a power consumption that is approximately half that of the capacity of the battery in
watt-hours. For example, a 25 watt camcorder will have very little impact on the life of a
battery rated at 50 watt-hours or greater. However, as the power consumption approximates
38
the capacity of the battery or greater, life expectancy will be diminished. As a comparison, 50
watt-hour batteries powering the aforementioned 25 watt camcorder may provide months of
additional service after 25 watt-hour batteries in the same application have expired. Thus for
maximum life, as well as the previously stated practical reasons, select a battery with twice the
rated capacity of the power consumption.
This rule is somewhat complicated by the introduction of batteries constructed of small cells
primarily designed for low rate discharge (like computers and cell phones). While these batteries may boast of capacities equal to those of larger batteries, the small cell size used in these
batteries is rated for delivering its capacity at much lower discharge rates. Due to the internal
impedance of these small cells, a discharge of 25 watts is often up to 3 times greater than the
discharge rate used to determine their rating (see The “Rating Game” discussed previously).
Over Discharge - Discharge current must never be allowed to continue after the battery has
reached the EODV or end of discharge voltage. Running a camcorder or especially a light
while the battery voltage is below the EODV can create a condition known as reverse polarity
which will irreparably damage the battery and reduce its overall life. (See Problem Appendix).
Therefore, never leave a battery powered piece of equipment unattended while it is running.
Moreover, always change to a fresh battery as soon as a ‘low voltage warning’ appears or the
InterActive battery indication signals for a battery change.
Battery Life
Physical Shock - Transporting batteries unrestrained in a large case or loosely in the trunk of a
car can create extremely high impact forces that will create conditions that will adversely
affect both life and performance. In addition to selecting a ruggedly designed battery, always
transport batteries in a fitted case or compartment. Maximum life will be attained when batteries are not dropped or excessively submitted to severe impacts.
Cell Type - Life expectancy is also a function of cell type. Certain cell formulations and constructions will trade-off as much as two thirds of comparable cycle life for other attributes such
as power density or cost. This is especially true of newer cell chemistries. Before selecting a
battery, make sure you consider its life expectancy relative to its other specifications and to
those of other similar batteries.
39
SAFETY HAZARDS
Assuming proper battery and charger design, the operation and charging of batteries is
extremely safe. Conversely, life threatening explosions and serious fires can result from failure
to follow the explicit safety guidelines presented by the cell manufacturers. Unfortunately, the
great majority of battery and charger manufacturers have responded to these critical safety
hazards by merely printing small warning disclaimers on their equipment and in the
instruction manual rather than designing safe equipment that would prevent these hazards
from occurring. If these warnings and danger labels are not adhered to in the manufacture
and use of any type of battery, serious damage and injury may result. All users of rechargeable
batteries should therefore be acutely aware of the following dangers.
Safety Hazards
Cold Temperature Charging
The fast charging of a cold battery is one of the most dangerous hazards associated batteries
and can result in a violent explosion. By way of example, when a NiCd battery is fast charged
at temperatures below +41˚ F (+5˚C ), the internal charging reaction can not proceed
normally and a significant portion of the charge current can be diverted into producing highly
explosive hydrogen gas within the cell. Cell manufacturers emphatically state, that to avoid
the risk of hydrogen gas explosion, the high rate charge current must be reduced or
terminated to the battery when the temperature of the battery is below +5˚C. Despite this
danger, every conventional charger now being manufactured can not properly identify a
potentially hazardous cold battery. These chargers can deliver to cold batteries charge currents
typically 10 times greater than the safety limits set by the cell manufacturer.
Every cell manufacturer, for every chemistry,
provides a specification for an acceptable charging
temperature range. Because cold temperatures
increase internal resistance and slow chemical
reactions, cold temperature charging of any
chemistry battery can be a potential hazard. When
the charger manufacturer warns: “Charge batteries
that are between +5˚C and +40˚C only” - he is not
kidding.
Anton/Bauer believes the risks of cold temperature charging are too great to be relegated
merely to a warning label. Therefore every Anton/Bauer professional battery has a unique cold
temperature protection circuit. There is never any risk of danger if a battery that is below the
safe fast charging temperature is placed on the charger. The cold temperature safety sensor in
the battery mates with the charger safety programs which then automatically control the
charge rates to remain well within the safe limits specified by the cell manufacturers. Thus,
when using an Anton/Bauer system, the threat of cold temperature hydrogen explosions are
virtually eliminated.
Again it must be stressed, except when using an InterActive battery with its cold temperature
protection circuit on a complimentary InterActive charger, a cold battery should always be
allowed to reach room temperature before being placed on a charger.
40
Fire Hazards
Unfortunately conventional batteries and chargers have been identified as the source of
potential hazards for years. After one such incident that almost resulted in tragedy, a major
television network mandated that cameramen not charge batteries in their hotel room. An
understanding of the conditions that can cause these disasters and the use of properly
designed batteries and chargers can virtually eliminate any possibility of a fire or smoke
hazard. The cause of all fire and smoke incidents can be basically grouped into these categories:
1 - Failure to terminate charge - The vast majority of incidents can be traced to a charger that
has failed to recognize that a battery has reached full charge. As explained in the Charger
Technical Section, one of the most critical functions of the charger is to recognize the
moment that a battery reaches full charge in order to terminate the high fast charge current.
Failure to terminate the fast charge current on time can have catastrophic ramifications. In
the case of nickel based chemistries, the continuing high current, is typically 10 times greater
than a fully charged cell can tolerate, and will produces inordinate amounts of heat. In the
case of lithium ion chemistry, the failure of the charger to recognize the termination point
forces the reliance on the backup safety circuitry in the battery. If that circuitry is damaged or
is improperly designed then the battery can go into a thermal run-away condition, bursting
the cell and igniting its electrolyte. If this sounds dramatic, for anyone who has not seen it
happen – it is.
2 - Slow Charging - A slow charger is a very simple device that delivers an appropriate and
safe rate of charge current only when it is connected to the specific model battery for which it
was designed. If a slow charger is connected to any other battery, particularly one with fewer
cells, less capacity, or a different chemistry, the battery could generate an abnormal amount
of heat that may be sufficient to cause a hazard.
Safety Hazards
A safely designed battery should always include a thermal fuse in the power circuit which
will disconnect the battery from the charger or any other external device in the event that
dangerous internal temperatures are detected.
3 – “Universal chargers” -– There are many chargers that can – or claim to – charge batteries
having the same looking case and connection as the original manufacturer. This can easily
mislead operators into believing that two chargers with very different characteristics and
capabilities are interchangeable. Only charge batteries with the charger designed for it by the
battery manufacturer. And only use batteries designed by the manufacturer of the charger.
There is no such thing as a “universal” charger in professional video. Every reputable
manufacturer has a different construction to its batteries and charger which cannot be
anticipated by another reputable manufacturer.
4 – Incompatible chemistry - Unless you have an InterActive charger, do not use batteries of
different chemistries (see Cell Formulation Section) on the same charger. Even though the
batteries may fit, chargers that use only + and – are usually incapable of identifying the type
of battery attached to them. In many cases some new chemistry batteries are constructed to
“fool” the charger into thinking that a battery is the same conventional NiCd battery for
which an older charger was originally designed. Moreover a charger may have the ability to
recognize the proper battery but not to reject an improperly designed or incompatible battery.
41
Only an InterActive charger is capable of both identifying a battery consistent with its
programming and rejecting a battery for which the charger was not designed.
5 - Blocking air circulation - For safety as well as reasons of battery performance and life,
batteries should always be charged in a position that maximizes free air circulation.
Specifically, batteries should not be grouped close together or left in a bag or case during
charging. Chargers should be operated on a counter, tabletop or bare floor – never on a
carpet. Likewise, other objects should never be placed on top of charging batteries or
the charger.
Safety Hazards
6- Physical Shock and External Short Circuits - Any professional battery can become a hazard
by releasing incredibly high rates of current if the battery is inadvertently short circuited.
A short circuit can instantly transform internal wires and connecting straps into red hot
elements. This has been known to happen when a battery is accidentally dropped. In such
cases the impact causes an internal collision between two or more cells sufficient to tear
the thin insulating sleeves thus creating a direct short. A pinched wire can create the
same disaster.
It has been shown that this type hazard can be effectively eliminated through preventative
design measures. Heavy duty fiber type cell insulating sleeves should be used as they can
survive repeated impacts that would cause plastic sleeves to fail. While more rugged insulating
sleeves are highly desirable, the best approach is to prevent major impacts from reaching the
cells or creating movement between the cells. As discussed in the Battery Construction
Section, a high impact thermoplastic unitized case will perform this function. It is also
important that all power conducting wires and straps are channeled in a manner to prevent
chafing or pinching under impact.
An external short circuit can create the same fire hazard as an internal short, however this is
more easily avoided. The external power contacts should be recessed and the battery should
include an externally replaceable and/or internal resetable fuse in the power circuit.
(Anton/Bauer InterActive battery/charger systems comply with all the safety recommendations suggested in this
Safety Hazard Section).
WARNING: Based upon reported incidents, so-called “equivalent” replacement batteries
and “re-built” batteries can represent a serious safety risk. After purchasing a battery and
associated compatible charger from one manufacturer, another may offer replacement
batteries that are “identical to the original batteries”, or offer to re-build your original batteries
to “like new” conditions. Such replacement or re-built batteries are at best a misrepresentation
and at worst a potential hazard.
Replacement, look alikes or re-built batteries may ‘appear’ identical to the original, and often
re-use or copy the original manufacturers’ cases, however the internal components, assembly
techniques and quality control are almost always quite different. In addition, the cell type
and formulation is almost always different from the original for which the charger has
been optimized.
42
Unfortunately such hidden differences do not become evident until it is too late. Initially these
“replacements” or “re-builds” only appear to be “equivalent”, while the internal differences
will eventually result in reduced performance and a life span that is usually only a portion of
the original battery. Most critically, these internal differences pose a serious safety risk that
have resulted in fire and explosion.
Having invested in a safe and compatible battery/charger system, it is hazardous (as well as
uneconomical) to utilize batteries not produced by the original manufacturer.
Safety Hazards
43
PORTABLE LIGHTING
The latest video camcorders are technological marvels that bear little resemblance to the
crude tube devices of the seventies. With the evolution of advanced CCD chips, digital signal
processing, and now digital recording formats, you would assume that video images being
viewed today are quite superior to those of a decade ago. Unfortunately this is often not
the case.
The camcorder only records the image; it is light that creates the image. Today’s cameras have
such high sensitivity and low noise that cameramen are encouraged to shoot with available
light in almost any situation. The problem, however, is not the quantity of light, but rather the
quality of the light.
Portable Lighting
Available light almost always involves illumination source – whether ceiling fixtures indoors or
the sun outdoors - coming from above. While this type of illumination is satisfactory for the
background, it creates a disaster with a person in the foreground. The horrors of available
light are familiar to everyone: dark eye sockets, glowing noses, giant chin shadows, radiant
foreheads, and exaggerated wrinkles. It’s not a pleasant sight.
An elegantly simple solution to this available-light problem has now gained wide spread
popularity. It is a tiny camera mounted ‘fill light’ that is designed to perfectly fill and thus
remove the shadows created by overhead lighting. The concept for such a light is easy to
understand. According to architectural specifications and actual location measurements,
virtually all interior locations are lit to within one f-stop of 40 foot candles. A survey of video
professionals further revealed that the vast majority of ENG ‘stand-ups’, interviews, and
foreground action always occurs within 1 to 2 meters of the camera. The perfect fill light
must thus produce about 40 fc at approximately 1-2 meters (5 ft.) with a beam angle
sufficient to cover all popular lenses.
The 50+ watt lights often used today are not much better than the 100 to 250 watt bulbs
used 15+ years ago. These lights totally overpower the subject with an unnatural search-light
effect reminiscent of interrogation scenes in 1940s movies.
A light output greater than 40 fc on the subject from the camera position overpowers the
available light creating the flattening “searchlight-in-the-face” look and also causes the lens to
iris down making the background muddy. Likewise, significantly fewer than 40 fc of light from
the camera will not effectively remove the shadows which are, by definition, those areas that
are not receiving the 40 fc of available light from above.
Studio lighting “models” the subject with light from both the front and above in comparable
proportions - which is exactly what the “40 fc perfect fill” can do in conjunction with the
existing architectural light. The proper fill light is one designed to work with available light to
create studio quality video.
The subtle ‘fill’ from this light perfectly matches the existing available light and miraculously
removes all offending foreground shadows without affecting background clarity or exposure.
No verbal account can begin to describe how this simple ‘fill’ can instantly transform any
available light location from a shadowy nightmare to an apparently ‘studio lit’ scene.
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By utilizing a high efficiency and precisely angled reflector, the Anton/Bauer Ultralight
consumes 30% less power than conventional lights of equal illumination. As a result the
required 40 fc of light is achieved with only 25 watts. (It’ is clear why those old 250 watt
lights were so horrible; they were using 10 times too much power.)
With such low power drain, the Ultralight can be powered from the same battery that powers
the camera or camcorder. Such a configuration eliminates the need for dangling cables or
additional battery belts. A PowerTap socket allows the light to be plugged directly into the
Anton/Bauer Gold Mount at the rear of all professional cameras. (Many professional cameras
include the Gold Mount directly from the manufacturer, however there is a Gold Mount
available for most every camera and camcorder). The additional current drain of the light
should not have a significant impact on battery run-time since the light is not on at all times
the camera is on. A battery providing 2 1/2 hours of operation will still typically deliver almost
2 hours with an Ultralight in a typical ENG situation.
The use of a 25 watt ‘fill light’ powered from the camcorder battery should not have a
significant impact on the selection of your battery/charger system. In most cases the battery
system recommended for a specific application will not be changed by the addition of a low
power fill light. However, the following guidelines should be considered when using a camera
mounted and powered light:
Portable Lighting
This fill light is not an “accessory” for an ENG/EFP camera but rather a “necessity” for
professional quality video and most major professional cameras/camcorder manufacturers
are now making such fill lights an integral part of the camera design. Working in close
cooperation with camera/camcorder manufacturers, the ULTRALIGHT 2 can be controlled
automatically by the VCR ‘Rec’ button to turn on and off simultaneously with the VCR. This
Automatique™ feature eliminates wasted battery capacity and, together with the low power
consumption, allows this light to be powered directly from the camera battery without any
significant reduction in camera run time. When it comes time to put the camcorder back
in the case, or if the light is not needed, the lamp base folds into the handle and
completely disappears.
1 - Do not ‘cheat’ on the aforementioned 2-hour minimum run-time objective. The watt-hour
capacity of the battery should be a minimum of 2 times the power consumption rating of the
camera/camcorder.
2 - You may want to consider a battery system consisting of two different size batteries. A
larger capacity, heavy duty type for indoors where fill light is needed, and a smaller capacity
for outdoors assignments. As an example, a 25 watt camcorder should be matched with a 50
watt hour battery. While a HyTRON 50 (50 watt hours) may be quite satisfactory for a fast
paced outdoor (no light) assignments, a HyTRON 120 would be a better power choice when
a fill light is being used.
45
3 - The additional power drain of a fill light is relatively insignificant except when the
cameraman inadvertently leaves the light on when tape is not running. It is important
therefore to develop the habit of turning the light off immediately after the tape is stopped.
The Ultralight Automatique feature is a standard feature of almost every professional
camcorder today and built directly into the camera’s Anton/Bauer Gold Mount to couple with
the VCR ‘roll’ circuit in the camera. The light can be controlled manually or automatically,
turning on/off with the VCR button on the camera eliminating wasted power.
4 - For greater distances from the camera to the subject, additional light output may appear
to be needed. However in most cases this does not mean that a higher wattage bulb is
necessary. Utilizing ‘spot’ type bulbs and focus adapters, the light output can be increased by
more than 10 times with little no increase in wattage. When distance between camera and
subject increases, the lens is usually at a longer focal length, or more narrow, viewing angle.
By matching the beam angle of the light to that of the lens, an enormous percentage of the
light that would otherwise be wasted is now concentrated onto the subject.
Portable Lighting
While the 25 watt bulb will cover the vast majority of interior ‘fill’ situations, there are
several instances where additional wattage and light output may be required. These include
the following:
1 - Outdoor “Daylight Fill” - In many cases a subject outdoors will be in an area or position
that is getting less light than the background or one side of the face may be more highly illuminated than another. This is basically the same situation as indoor fill except the illumination
level to be filled may be 20 or more times as bright. This situation can typically be addressed
by an 85 watt spot (narrow beam angle) with a dichroic ‘daylight’ color correction filter. Such
an arrangement, which is almost equivalent to an old inefficient style 30 volt 250 watt ‘sungun’, can typically provide an “f- 8” lens stop at a reasonably close distance. High efficiency,
low wattage HMI lights, such as the Anton/Bauer UltraDAYlight head module, can deliver
more than twice the footcandles at 5600°K for the same power as tungsten sources.
2 - Distant Interior Wide Angle - The 25 watt 60° beam angle universal fill light can cover an
individual or typical “two-shot” (interviewer/subject) at any distance up to about 10 feet (3
meters) with even the widest viewing 4.8mm lens. However, to cover a larger group of people (wide angle lens) at distances of 13 to 20 feet (4-6 meters) will require an 85 watt flood
set-up (an 85 watt flood bulb or 85 watt spot bulb with wide angle adapter). In those rare
instances where a large group at 20 or more feet from the camera must be covered, a quick
switch to a 200 watt 30 volt head module may be required. Such a bulb can be powered by a
standard “30 volt” (28.8 volt) battery belt, or two regular ProPac 14 video batteries with a
special “30 volt” lighting holder.
3 - Exterior Night - The most prolific mis-use of high wattage lights occurs at night covering
“disaster scenes”. Contrary to the popular conception, less light should come from the
camera as an exterior scene gets darker. Due to the recent advances in camera technology,
high-voltage/high-wattage lights in these situations will produce flat video and destroy
background detail. Greater realism, clarity, and overall quality can usually be achieved with
lower power 25 watt bulb even if 6 dB or 9 dB of gain is necessary.
46
PROBLEM APPENDIX
(with Solutions)
Batteries appear to be the most misunderstood aspect of professional video, possessing a
“complex personality” that over the years has spawned an extensive popular mythology that
unfortunately is more fiction than fact. This has led to a large number of battery problems
that has compromised many a video production. Throughout this handbook we have
attempted to clarify most of these misunderstandings in a practical and topical manner.
The following addresses more fully the most widely discussed and misunderstood
rechargeable battery problem topics.
MEMORY
NiCd “memory” is probably the most widely misunderstood of all battery anomalies.
The introduction of new chemistries has led to a great deal of talk about any new battery
being “memory free”. As we will see, many of the same phenomena which have resulted in
the label “memory” in NiCd can exist in both NiMH and lithium ion. In fact, most of the talk
of memory comes from those manufacturing or using the wrong batteries and chargers for
the application.
Problem Appendix
A major source of the confusion surrounding “memory” stems from the fact that there are
two totally separate phenomena that have been called “memory”. One of these is the “true”
memory phenomenon which virtually never exists in practical application. The other is actually
a ‘voltage drop’ problem that has become known as a “memory” problem based on its
symptoms. It is this voltage drop that has been the long time subject of “memory” myth
in the video industry.
The “true” memory was first observed by NASA while monitoring an orbiting satellite. Each
day at precisely the same times, this satellite alternately passed from sunlight, where its NiCd
batteries (not the same type as used in batteries for professional video) were solar charged,
into darkness, where the batteries were called upon to power the craft. After many cycles of
this precise duration partial discharge/charge routine, the scientists found that the battery
would refuse to deliver power beyond that point to which it had previously been repetitively
discharged. In other words, the battery “memorized” the point of partial discharges and then
refused to give energy beyond that point if called upon to do so. This story has given rise to
the myth that batteries should always be fully discharged before being charged in order to
prevent the mysterious “memory” from robbing the remaining capacity.
This type of memory never occurs in the video industry or any other industry for that matter.
This rare memory phenomenon only results when the amount of the repetitive partial
discharge is precisely identical each time, as occurred in the satellite. Relating this to video, a
battery would, for example, have to be discharged for exactly 23 1/2 minutes at the exact
same rate each day and then recharged each night for a week or more before this type of
memory developed. Clearly nothing even close to this could ever happen. Yes, batteries are
frequently only partially discharged and then recharged, but never in the precise manner
necessary for true memory to be developed.
47
Problem Appendix
The “memory” so often mentioned in the video
industry is not really a loss of capacity nor does it
result from repeated partial discharges. It is in
reality a voltage depression phenomenon and fig
5 is a graphic representation. At the so-called
MEMORY DEPRESSION
“memory” depression point, the voltage of the
battery will drop about 1.2 volts. Figure 5 curve
‘A’ represents a “12 volt” nominal battery on a
typical camcorder. Note that at the “memory”
point the battery voltage drops below the camera
cut-off voltage and thus the camera will stop. It
appears that the battery has no more capacity.
Figure 5
However this is not true. As can be seen, the
battery can still deliver full capacity to the
specified EODV at this lower voltage without a problem. The problem is the camcorder,
which can not use this capacity. (Called “unavailable capacity”. See also Battery Voltage
section). This is why this type of “memory” became known as a “loss of capacity”, because in
this misapplication it does indeed result in a loss of capacity.
Curve ‘B’ represents the proper “14.4 volt” nominal battery for this camcorder. Note that the
so-called “memory” point and associated voltage depression results in no loss of capacity.
So this type of “memory” really is not a “loss of capacity”. But where does this voltage
depression come from and why is it called “memory”, and why do so-called dememorizers
or dischargers seem to alleviate this problem?
This so-called “memory” problem may be traced to a “transformed” or secondary alloy of
Nickel Cadmium which can be developed under extremely poor charging conditions. Very
simply, when a fully charged NiCd battery remains on a slow charger or many fast chargers, it
is receiving a ‘trickle charge’ which is designed to prevent self discharge. Unfortunately over a
period of time, this trickle charge can gradually transform the crystal structure a portion of the
nickel and cadmium plates into secondary alloys. While a normal NiCd has a nominal voltage
of 1.2 volts per cell, these secondary or “rogue” alloys produce a lower characteristic voltage
of approximately 1.08 volts per cell.
Now consider a 10 cell (12 volt) VTR type video battery that has developed some of the
transformed alloys. It is really two-batteries-in-one: part of the battery is a “12 volt” nominal
NiCd and the rest is a “10.8 volt” nominal secondary alloy. When this “dual voltage battery”
is placed on a camcorder, the power will always be drawn from the higher voltage section
(normal) first and everything appears normal. Once the normal plate chemistry has been
discharged, power will begin to be drawn from the lower voltage alloy section of the plates.
Of course at this point the voltage will fall to the characteristic voltage of the transformed
alloys, which is insufficient to keep the camcorder operating.
There appears to be a mysterious loss of capacity and the battery is returned to the charger.
The question now is: “What is being recharged”? The answer is: not the rogue alloy parts of
the battery. Because the camcorder could not discharge the transformed chemical structure of
the battery, it is still fully charged and intact. Only the “normal” section of the battery is being
recharged. Therefore, the next day the battery will perform exactly as it did on the previous.
48
First, everything will appear normal and then all of a sudden the camcorder will mysteriously
stop at the same point as it did before as if it had “memorized” the point at which the
capacity was lost. This is where the misnomer “memory” comes from. Likewise, this is where
the myth of the discharger was born giving rise to the totally false notion that batteries should
be discharged fully before being charged.
Now that the mysterious phenomenon of “memory” is understood, the principle of the
discharger becomes apparent. Because the camcorder can not discharge the rogue alloy in a
“12 volt” nominal battery, it will remain there “forever”. As a matter of fact, the situation
actually gets worse as each subsequent trickle charging will create even more rogue alloy. In
reality the rogue alloy is a perfectly legitimate battery. If the afflicted battery is connected to a
device that can properly run down to the correct full discharge voltage of 10.0 volts, the
battery will be totally discharged, rogue alloy and all. Now when it is recharged it will be
100% normal NiCd and the missing capacity magically returns. Thus the creation of the
“discharge-before-charge” myth is as follows:
1 - A camera/camcorder is powered with the wrong battery that has a full discharge voltage
below the cut-off voltage of the camcorder.
3 - By placing the battery on a device that can discharge the rogue alloy, the battery becomes
100% normal alloy when recharged and the “lost capacity” miraculously returns.
Take another look at fig 5 Curve ‘B’. Note that when the correct battery with the proper
voltage range for the camcorder is used, there is no “memory” problem. In essence, the
camcorder performs the function of the “dememorizer” or discharger by fully discharging and
erasing the rogue alloy every time the battery is used. It should be absolutely clear that the
“memory” problem and the associated ‘discharging-before-charging myth’ are both the result
of using a “12 volt” nominal battery in applications calling for a “14.4 volt” nominal battery.
Moreover, when using the proper voltage battery, discharging fully before charging is not
only unnecessary, it is not recommended (See section below).
Problem Appendix
2 - When trickle charging creates the rogue alloy, the camcorder can not discharge it. Thus
the rogue alloy remains intact and the battery appears to progressively lose capacity.
DISCHARGE-BEFORE-CHARGE
The above section on “memory” fully explains the origin of the discharge-before-charge
myth and why it is unnecessary when using the correct battery for the application.
However if a discharger is currently being used to test a battery performance in the field,
it is imperative that precautions are observed to avoid permanent damage to the battery
and possible explosion.
A light bulb or resistor must never be used as an unmonitored load to discharge a battery as
this will take the battery down to 0 volts. Fully discharging a battery to 0 volts may damage
the battery irreparably and could cause a serious explosion. A video battery consists of ten or
more cells in series. As a battery approaches the end of discharge, one cell will always reach
total depletion before the others. Once this first cell reaches 0 volts, the remaining cells may
still have some energy and will continue to deliver power to the load. This current passes
49
through the depleted cell and will actually begin to charge the depleted cell in the wrong
direction. This drives the cell into reverse polarity which will damage and weaken the cell as
well as create explosive hydrogen gas.
When applied to rechargeable batteries the expressions “full discharge” or “deep discharge”
never mean a discharge to 0 volts but rather a discharge to the specified EODV or End of
Discharge Voltage (sometimes called the ‘full discharge voltage’). Therefore a discharger must
have an automatic cut-off set at the EODV of the battery or slightly below. When the battery
voltage reaches this value, the load must be instantly disconnected from the battery to avoid
damage and injury.
For reference, the EODV voltages recommended for discharger cut-off are:
“12.0 volt” nominal battery = 9.0 to 10.0 volts
“13.2 volt” nominal battery = 10.0 to 11.0 volts
“14.4 volt” nominal battery = 11.0 to 12.0 volts
Problem Appendix
Remember: When using the correct battery for an application, discharging before charging is
not only unnecessary, it is strongly not recommended. Such discharging serves no purpose
other than to detracts from the overall cycle life of the battery.
For those who continue to ‘believe’ in the existence of “memory” problems despite the aforementioned scientific evidence to the contrary, the following suggestions are offered:
• Feel free to “exercise” your batteries every month or two by using a discharger with the
proper cut-off circuit. After the discharge is completed, allow the battery to ‘rest’ for at least 2
to 4 hours before being recharged. Such an occasional discharge should have no significant
adverse effect on the battery.
• Place ‘name labels’ on your batteries such as “Monday”, “Tuesday”, etc, or just “A”, “B”,
“C”, etc.
On Monday, begin with the “Monday” or “A” battery and try to use it until depletion (low
voltage warning in the camera), and then switch to any other battery. On Tuesday, start with
the “Tuesday” or “B” battery and again try to use it until depletion before changing to any
other battery.
Continue in this manner each successive day. This practice will guarantee that each one of
your batteries will receive a full discharge during operation at least once a week. For those who
feel for some reason that periodic discharging is beneficial, this is the safe and practical way to
do it without reducing the life or performance of the batteries. In essence, by using the proper
voltage battery, the camera performs the function of the perfect discharger.
SELF DISCHARGE
A fully charged battery, after it is removed from the charger, will experience a phenomena
known as self discharge. Due to an internal characteristic of any rechargeable cell, it will very
slowly and steadily lose its charge over a period of time. At room temperatures, a NiCd or
NiMH battery will be expected to typically lose up to 5% of its capacity in the first 24 hours
50
and then about 1% each day thereafter. Under normal circumstances self discharge can be
considered insignificant as almost 90% of full charge capacity should be available after more
than a week away from the charger.
Lithium ion batteries will retain a greater degree of their charge for a longer period. However,
it should be noted that the charged state is the worst condition to store batteries long term,
especially lithium ion. The effects of “unrecoverable capacity” (discussed in the Cell
Formulation Section) are significantly worse in a charged battery. While the effects of storage
are virtually nil in a NiCd and less in a NiMH, long term storage of a lithium ion battery
should be avoided. Colder temperatures will significantly slow the process for all batteries
while elevated temperatures will accelerate self discharge.
The effects of self discharge can be fully negated by employing an InterActive charger with its
Lifesaver maintenance mode. This proprietary program provides only the appropriate amount
of low rate charge sufficient to offset the self discharge rate of the battery. In this way the batteries can remain indefinitely on the charger, 100% charged and free from the deleterious
effects of self discharge and resulting cell imbalance.
IMBALANCED BATTERIES
Problem Appendix
An imbalanced battery is characterized by having individual cells in the battery pack that are
at different states of charge. This results from the fact that of the ten or more cells that make
up a nickel based battery, each is likely to self discharge at a slightly different rate and over a
period of time each cell will exhibit a slightly different capacity or state of change. This minor
problem becomes major when one or more cells exhibit an anomaly known as accelerated self
discharge in which case the magnitude of the imbalance can become extreme and render the
battery useless.
A lithium ion battery may also become imbalanced due to various factors - manufacturing
tolerances when the cell was made, mismatching of cell capacities when the battery pack was
made, extended storage periods resulting in cells of different “recovered capacities”, internal
failures in one of the cells, or by varying loads placed on the cells created by the battery’s own
monitoring circuitry.
Unfortunately, it is impossible to address an imbalanced lithium ion battery. Assuming the safety
circuits of a lithium ion pack are properly designed and operating, the lower capacity of even
one cell in a pack can drive the entire pack to shut itself down. Since only one cell at EODV
will shut down the pack (and therefore the camera) any imbalance in a lithium ion battery
creates a shorter run time. The weak cell may also shut down charge to the entire pack when
it is fully charged and the rest of the pack is only partially charged. The resulting spiral of poor
performance is but one drawback of lithium ion chemistry. The following discussion relates to
nickel based chemistries only.
Cells with some level accelerated self discharge are quite common and the above course of
events occurs all too frequently, however this need not happen. Batteries with such cells can
provide satisfactory service if the correct measures are taken. Of course proper battery
construction can effectively eliminate the major cause of accelerated self discharge but when
this condition does exist, accelerated self discharge can be negated (only in nickel based
51
chemistries) with a maintenance charge and any imbalances can be corrected with a special
equalizing charge.
Problem Appendix
Equalizing Charge - Due to both normal and accelerated self discharge, a battery can become
imbalanced ( see above ). Conventional charging can not address this problem as the fast
charge current must be terminated when the first cells reach full charge otherwise they would
be damaged. Any other cells that have not reached full charge at this point will remain in the
less-than-fully-charged condition. Thus any imbalance that existed before charging will still
exist after charging. In addition, conventional charge termination technology can be totally
mislead by a severely unbalanced battery and fail to cut-off high rate charge current resulting
in battery destruction and the risk of fire.
This apparent paradox and hazard has been eliminated through InterActive charge
technology. No matter how severe the imbalance, the internal sensors in the battery will
always identify the first cell reaching 100% charge and terminate the fast charge thus
eliminating all risk of hazard and damage to the cells. Immediately after the fast charge
current is terminated, the charger microprocessor enters the equalizing mode. Based upon data
from the battery Microcode circuit and sensors, and charge data collected during the
preceding fast charge cycle, the battery receives an equalizing charge cycle that consists of a
precise charge rate designed to bring up to 100% those cells requiring additional charge
while causing no damage to those cells that have already reached full charge. When all cells
have reached 100% charge and the battery is fully balanced and equalized, the equalizing
charge rate is terminated and the maintenance mode commences. When using an Anton/Bauer
InterActive charger, this equalizing mode is a standard feature of every charge cycle thus
assuring complete safety and a 100% charged and balanced battery every time. While the
equalizing mode can correct any existing imbalances, the maintenance mode is designed to
prevent imbalances from ever developing.
Maintenance Charge - Assuming a conventional charger has successfully identified the full
charge status of the battery and terminated the fast charge current, it will classically do one
of two things. It will either shut off all charge current (and essentially disconnect from the
battery) or provide a continuous ‘trickle charge’ for as long as the battery remains on the
charger. Both of these alternatives create serious problems.
Terminating all charge current is identical to removing the battery and placing it on a storage
shelf until it is needed. This allows the cells within the battery to experience both normal and
accelerated self discharge, as the case may be, which creates the highly undesirable scenario
described in “Imbalanced Batteries” above. Even if accelerated self discharge is minimal,
normal self discharge can still rob a significant amount of run-time depending on the storage
time before use and the storage temperature.
After fast charge termination, many conventional chargers place the battery on a continuous
‘trickle charge’ for as long as the battery remains on the charger. This trickle charge is
designed to fully compensate and thus negate virtually all self discharge, both normal and
accelerated, keeping the battery fully balanced and charged. This concept is valid in theory,
however the trickle charge unfortunately has serious side effects that are actually more
detrimental to the battery than self discharge. Trickle charging creates heat that will elevate
the cell temperature of a typical video battery to over 45˚ C (113˚ F) which causes the cell to
52
deteriorate at a rate 5 to 10 times faster than normal. In other words, the constant trickle
charge is causing the battery to age up to 10 times faster than normal, and a battery that
would be expected to provide 2 or more years of service may fail after only 3 months of use.
In addition, these elevated temperatures also reduce charge acceptance resulting is reduced
capacity. Lastly, extended trickle charging is the major cause of the phenomenon known as
“memory”. The bottom line is that trickle charging is one of the worst things you can do to a
battery, from both an economic as well as a performance perspective.
This is the proverbial “damned if you do and damned if you don’t” situation. If the battery
does not receive a some charge, it will self discharge and become imbalanced. On the other
hand, if the battery is given a trickle charge, self discharge and imbalances are prevented but
performance will be impaired and battery life can be reduced by 80%. Confronted with this
paradox many years ago, Anton/Bauer developed a maintenance charge regime that could
prevent self discharge and imbalances without the heat generation and accelerated aging
associated with conventional trickle charging. After the battery has been charged and fully
balanced by the equalizing mode, the battery is placed in the exclusive Lifesaver maintenance
mode for as long as the battery is on the charger. The microprocessor, with data from the
battery, creates the precise Lifesaver pulse profile to keep the battery 100% charged and
balanced with virtually no temperature elevation or accelerated aging. The battery should
remain on the charger until it is needed. This can be days, weeks, or even months.
Problem Appendix
53
TECHNICAL UPDATE: FUEL CELLS
Fuel cells may very well represent the future of portable power. In 2003 the Bush
administration backed almost 2 billion USD to fund research, infrastructure development
and R&D of hydrogen energy technologies.
A fuel cell is essentially an “engine” which converts hydrogen and oxygen into electricity and water.
By no means a 21st century technology, the first fuel cell was invented in 1839 by Sir William
Grove about 40 years after Alessandro Volta invented the first battery. In the early 1960s GE made
the first PEM (polymer electrolyte membrane) used in the Gemini spacecraft.
Technical Update
Recently fuel cells have received a widespread buzz with a great deal of discussion of the
“hydrogen highway” and the “hydrogen economy”. Hydrogen unfortunately does not normally
appear by itself in nature but rather as part of other compounds and therefore must be extracted
or re-formed. Indeed the benefits of finding efficient methods of reforming hydrogen are
inescapable – a virtually limitless supply of fuel which can be used in energy producing devices from
which the only by-products are essentially energy and pure water. However today this reformation
process requires substantial amounts of fossil fuel to extract hydrogen and there is little
infrastructure to process, store and deliver hydrogen as an alternative energy source. Thus, more
energy from fossil fuel is required to reform and deliver Hydrogen than hydrogen can yeild.
As the digital revolution beginning in the 80’s led the improvement of batteries, the development
of alternative energy transportation technology is driving the development of fuel cells. So the
research and development has been largely focused on the automotive industry where size, weight
and cost are not as critical as in portable appliances – such as computers or camcorders.
Fuel cell technology may become increasingly important as the cost of fossil fuels increase and its
supply decreases and a fuel reformation methodology is developed to economically support the
supply of hydrogen (or other fuels). In the meantime there will be a great deal of effort made to
show that fuel cells could be a viable alternative energy source, in an attempt to jump start a new
energy paradigm – the release of the “hydrogen genie”. Along the way, though, there will be a
great number of very practical hurdles to overcome.
The following discussion addresses some of the questions we have been asked regarding the
application of fuel cells to professional video.
Entry Cost. A PEMFC of about 60 watts with a fuel supply capable of about 140 watt hours of
operation can be expected to cost about 3-4 times that of a battery supplying the equivalent
runtime. A 60 watt 6.5 lb fuel cell, a couple of fuel blocks, and the re-fuelling plumbing to
hook up to a regulated hydrogen tank would cost well in excess of two to three times that of
a comparable battery and charger system.
Ongoing costs. Because hydrogen, the most common element in nature, does not occur by
itself in nature, it must be “re-formed” from another source. Today that source is primarily a
by-product of burning natural gas. Stored hydrogen is not cheap. The cost of bottled
hydrogen is many times more expensive than electricity obtained from the power companies.
A 2 lb. 140 Wh hydride canister would cost about 50¢ to fill from a hydrogen tank. The cost
54
to charge a 160 Wh battery is less than 6¢ or almost 10 times less. Over 500 operating cycles
refilling a PEMFC fuel block will cost more than $250. Methanol in solution may ultimately be
a viable and economical fuel, but for now, the cost of fueling a fuel cell still cannot compete
with the economics and global accessibility of electricity. Longevity of a PEMFC has yet to be
determined in field operation.
Size. A PEMFC capable of supplying 60 watts for about 2 1/4 hours (140 watt hours) would
be about 150 cubic inches (1.64 liters). A battery capable of similar runtime (and much
greater load capability) is about 80 cubic inches (1.29 liters) or about 46% smaller.
Weight. The same theoretical PEMFC as above might weigh about 6.5 lbs (2.95kg). A battery
capable of similar runtime (and much greater load capability) would weigh about 3.5 lbs.
(1.59kg) or about 46% lighter.
Convenience. The PEMFC used in the above examples could power a typical 25-35 watt
camera. However, regardless of the operating need, the operator is always required to carry
6.5+ lbs on the camera… even for a 5-minute shoot. As well, the identification of hydrogen
sources becomes an added logistic issue to the planning for any location production. Filling
2 lb hydrogen fuel blocks from a high pressure gas bottle likely will not be permissible in a
hotel room.
Technical Update
Lack of supporting infrastructure. The fuel source to charge a battery is one of the most
ubiquitous in the world – electricity. There is no corresponding infrastructure for the supply of
hydrogen or other fuels such as methanol. While bottled hydrogen can be obtained in most
major cities in purities required for fuel cells, it typically will not be sold to individuals. A high
pressure (~2200psi) storage tank requires a regulator and piping for safe handling and refilling
of a PEMFC hydride fuel block.
Performance. Operating conditions are extremely important to a PEMFC. Humidity, for
example, needs to be within a very tight range to keep the membranes critical to the
operation of the device from either drying out or saturating with water. Dust can also be a
problem. Temperatures below 30°F and above 100°F are prohibitive to fuel cell operation.
Today’s prototypical PEMFCs can not compare to the durability, wide range of operating
conditions and load capability of a professional video battery.
E fficiency. Today’s fuel cells are relatively inefficient, capable of delivering only a portion of
their potential especially those that operate in ambient environments; that is, without forced
air or oxygen feed. A portable ambient air PEMFC design could be expected to supply about
60 watts but at almost double the size and weight of a battery that is capable of supplying
almost three times the output.
Operating limitations. The theoretical example PEMFC above at 60 watts could likely be
capable of short duration maximum loads of around 75 watts. Any more, and depending on
the construction and electronics in the device, the device would “fold back” much as a AC
mains adapter (power supply) will do if overloaded – essentially shutting down. A 45 watt
camera and a 50 watt light are well beyond the capability of any small fuel cell product
currently contemplated. This limitation makes the PEMFC unsuitable for professional video
55
applications, including any combination of high wattage camera (>25 watts) and peripherals
such as on-board lighting (25-85 watts). By contrast the example battery above will power
continuous loads of up to 140 watts or 180% more load capability.
Transportation restrictions. Unlike restrictions governing size or quantity for certain batteries
(like lithium and lithium ion) all practical fuels (hydrogen, methanol) for fuel cells are
restricted in their transport. For example, hydrogen stored in any form, including hydride
bottles, is currently not allowed in passenger compartments of aircraft and must be
transported under special manifest as a flammable gas, solid (for hydrides), or liquid
(methanol). While this may change as methods of producing reliable storage devices are
improved, at this time travel and shipping logistics – air and rail – are severely limited.
Technical Update
The following pages compare a PEMFC to a field proven Ni-MH and lithium ion batteries.
Service life cannot be compared as the longevity of PEMFCs have yet to be proven in field use.
The promise of improvements in fuel cell products and the development of a worldwide
re-fueling infrastructure may provide a reasonable alternative in the future for batteries.
Until then, the performance, cost, size, weight, service life and proven reliability of a
professional video battery are beyond the capabilities of today’s early fuel cell designs.
A PEMFC product versus HyTRON 120
120 watt hours
BATTERY
160 watt hours
BATTERY
COMPARISON
+25 watt hours
145 watt hours
FUEL CELL
COMPARISON
-15 watt hours
145 watt hours
FUEL CELL
6.7 lbs
5.5 lbs.
+1.2 lbs
6.7 lbs
3.4 lbs.
+3.3 lbs
150 cu. in
75 cu. in
+75 cu. in
150 cu. in
79 cu. in
+71 cu. in
~6¢/cycle
~$.40/cycle*
145 watt
-80 watt
CHARGE COST
~$.50/cycle
CHARGE COST
~6¢/cycle
~$.40/cycle*
MAX POWER
60 watt
~$.50/cycle
MAX POWER
175 watt
-110 watt
Fuel cell difference:
25 more watt hours achieved at:
• TWICE the size
• 22% more weight
• about 10 times more operating cost
• 65% less load capacity
*500 cycles = $200 more operating cost
56
A PEMFC product versus DIONIC 160
60 watt
Fuel cell difference:
15 less watt hours achieved at:
• TWICE the size
• 97% more weight
• about 10 times more operating cost
• 57% less load capacity
*500 cycles = $200 more operating cost
How does one determine which battery is “best”?
It is important to recognize that choosing a battery system today is as important a decision as
deciding on a recording format. In most cases the choice of batteries outlasts the choice of
cameras. Many broadcasters who started with NPs when the very first BetaCams appeared
(because they got them “with the cameras”) are still dealing today with problems which were
successfully eliminated by Anton/Bauer 20 years ago.
The “best” battery is one which can be consistently and dependably used in every way the
operator wishes to use his equipment. The battery to power a 40 watt digital format camera
with an on-camera light is not necessarily the same battery to power a 25 watt camcorder
without a light.
A battery system, with features adopted by every major equipment manufacturer, consisting
of batteries of multiple sizes, chemistry and cost that can all be addressed on a single
upgradeable charger is the only “universal” solution. Ultimately, each application and operation is different and should demand different battery types.
Technical Update
Ask the right questions:
• Which battery format offers the most flexibility and compatibility with today’s equipment?
• What sizes and types fit the type of shooting that I do? Do I only do one type of
videography?
• Can I mix different sizes and chemistries on the same charger?
• Can I effectively operate on-camera lighting?
• Which format and battery type is the most cost efficient? Determine both the initial cost and
the cost over time to operate and replace batteries?
• Which battery format can adapt to new technologies as they arrive?
No one battery in video, or in any industry, can be called “universal”. In a video operation different operating conditions, different shooting requirements and individual preferences call for
different batteries at different times. The days of having only one size or type of battery have
long past.
Today the decision of which battery to use in professional video is one of format.
A battery format which offers the technology of a wide variety of sizes, types and
chemistries, which can be used on equipment from any manufacturer, and which
offers the ability to mix and match batteries safely and reliably on a
single charger - now and in the future.
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The worldwide standard ®
For information contact Anton/Bauer or any Anton/Bauer dealer or distributor worldwide.
Anton/Bauer, Inc. 14 Progress Drive, Shelton, Connecticut 06484 USA • (203) 929-1100 • Fax (203) 925-4988 • www.antonbauer.com
Anton/Bauer Europe, B.V. Eurode Business Center, Eurode-Park 1, 6461 KB Kerkrade, The Netherlands • (+31) 45 5639220 • Fax (+31) 45 5639222
Singapore Office - Anton/Bauer 6 New Industrial Road, # 02-02 Hoe Huat Ind. Bld., Singapore 536199 • (65) 62975784 • Fax (65) 62825235
The following are trademarks of Anton/Bauer, Inc.: ACS, ADM, Anton/Bauer, Anton/Bauer logo and parrallelogram design, Automatique,
DataTap, Dionic, Gold Mount, HyTRON, Impac, InterActive and design, LifeSaver, Logic Series, Logic Series logo, Maxx man logo design, MicroCode,
PowerStrap, Probe, Proformer, ProPac, RealTime, SSP, Satellight, Snap-On, Stasis, Titan, TrimPac, Ultrakit, Ultralight,
“The power behind the best cameras capturing the best images in the world”, “The worldwide standard”,
“The quality standard of the video industry”, and “There should always be choices. It makes it easier to recognize the best”.
Due to continuing product development, all specifications and prices are subject to change without prior notification.
Customer Service: 1-800-541-1667 or (203) 925-4991 • Fax: (203) 925-4988
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