The large UPS battery handbook
Reference handbook
The large UPS
battery handbook
The large UPS
Understanding your UPS battery
can extend its life, prevent
costly downtime, and save time
and money.
It’s well understood that the battery
in a UPS is the most vulnerable part
of the system. In fact, battery failure is
a leading cause of load loss. Knowing
how to maintain and manage your
UPS batteries will extend their life and
save you time and potential trouble
in the future.
Improvements in battery technology
have been evolutionary rather than
revolutionary. Capabilities such as
advanced charging regimens, software
management for accurate remaining
life information and firmware adding
intelligence to batteries have reduced,
but not eliminated, the risks inherent
in depending on any battery. As a result,
it’s prudent, if not essential, to take
a close look at what may be increasing
your risk of unexpected load loss
from a failing UPS battery. After all,
even large installations with many
batteries are vulnerable to the failure
of a single battery.
The large UPS battery handbook
Table of Contents
Table of contents
UPS battery overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
VRLA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Lithium-ion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Other common causes of UPS failure . . . . . . . . . . . . . . . . . . . 3
VLA/flooded-cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Battery arrangement and power . . . . . . . . . . . . . . . . . . . . . . . 4
Battery facts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Four factors that affect battery life . . . . . . . . . . . . . . . . . . . . . 5
Battery disposal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Battery maintenance for extended life . . . . . . . . . . . . . . . . . . 6
Battery safety . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Battery FAQ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Eaton battery products and services . . . . . . . . . . . . . . . . . . . . . 10
Eaton battery services overview . . . . . . . . . . . . . . . . . . . . . . 10
Battery preventive maintenance . . . . . . . . . . . . . . . . . . . . . . 10
Eaton batteries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Why Eaton batteries? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Eaton Cellwatch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Thermal runaway . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Extending battery service life . . . . . . . . . . . . . . . . . . . . . . . . 12
Eaton PredictPulse . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Customer Support Center . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Customer success story . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Battery glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
The large UPS battery handbook
There are primarily three
kinds of batteries used in
lead-acid (VRLA), also
known as sealed or
maintenance-free lithiumion batteries, and vented
lead acid (VLA) (also
called flooded-cell). VRLA
batteries usually have
lower up-front costs but
have a shorter lifetime
than VLA, usually around
five years. Flooded-cell
batteries require more
advanced maintenance
but have a longer lifetime,
up to 20 years. Lithiumion batteries are smaller
and lighter than the above
types, and have changed
the traditional status quo
for UPS use. Costs are
similar to VRLA, and
new energy storage
applications with UPS
systems, such as gridsharing and peak shaving,
are now viable. These
new capabilities provide
more than just backup
time, and can now
contribute to significant
cost savings for the
user in their day-to-day
VRLA batteries are sealed, usually within
polypropylene plastic. They were developed
because they have the advantage of containing
no sloshing acid that might leak or drip out
when inverted or handled roughly. The term valveregulated refers to the method of gas release. If the
gas pressure becomes too great inside the battery,
the valve will vent when it reaches a certain pressure.
During the charging of a lead-acid battery, hydrogen is
normally liberated. In a vented battery, the hydrogen
escapes into the atmosphere. In a VRLA battery, the
hydrogen recombines with oxygen inside battery,
so water loss is minimized. Under normal float
conditions, virtually all the hydrogen and oxygen is
recombined. Re-sealable valves vent non-recombined
gases only when pressure exceeds a safety
VRLA batteries are frequently
used in UPS or other high-rate
A VRLA battery is distinguished from a flooded-cell
battery by the rate at which oxygen is evolved from
the positive plate and diffused to the negative plate,
ultimately forming water. This rate is several orders of
magnitude faster than a flooded-cell battery. Because
water can’t be added, its recombination is critical to
the life and health of a the battery. Any factor that
increases the evaporation rate or water loss—such
as ambient temperature and heat from the charging
current—reduces the battery life.
Positive flag
Extruded intercell
welded connection,
low resistance
current path
Strap joining
plates in
pasted plate
lead alloy
Internal and external components of a valve-regulated lead-acid (VRLA) battery
The large UPS battery handbook
3. VLA
Lithium based batteries have multiple significant benefits
over alternative DC storage techniques for UPS applications.
The technology has matured in heavy duty applications like
electric vehicles, and is considered ideal for critical power
backup. Small size and light weight are the primary benefits,
but additional features like built-in battery management (not
just monitoring), make lithium-ion an attractive alternative to
traditional batteries.
VLA or flooded-cell batteries have thick lead-based plates
that are flooded with an acid electrolyte. This is a highly
reliable design—failures normally don’t occur until halfway
through their 20-year pro-rated life, at which time the failure
mode is most often a short circuit. This situation is not an
extreme emergency because any one shorted cell only affects
overall reserve time by a very small percentage. However, while
they’re very reliable with a long life, there are downsides to
flooded-cell batteries. They require more safety measures and a
space-consuming separate battery room to use.
In addition, their high cycle-count (charge-discharge cycles), and
faster recharge times compared with lead batteries allows their
use in non-traditional UPS applications, like grid sharing, peak
shaving, and industrial or process control support.
The battery management
system is deployed in each
battery, as well as in a system
level master controller. It
manages charge current,
voltage, and cell voltage
balance, while making
adjustments as necessary
to eliminate any chance
of overtemperature. If
temperatures rise above safe
levels, the management system
will independently disconnect
the battery or string via multiple
different disconnection means,
and notify the user via the
battery cabinet monitor, and an
alarm on the UPS.
Overall, a lithium-ion battery
system provides lower TCO
through comparable Capex
costs, and Opex savings via a
longer replacement interval, and
its ability to operate at higher
ambinet temperatures.
Lithium-ion battery systems
provide a reliable and flexible
solution that ensures 24/7
system uptime
Regardless of the differences in UPS battery types, both
require monitoring and maintenance to ensure maximum life
and system availability.
Flooded-cell batteries require more advanced maintenance but have a
longer battery service life
Other common causes of UPS failure
Did you know? Batteries may be the number one contributor to UPS failure,
but these are three other vulnerable components that shouldn’t be overlooked.
Capacitors: A capacitor is a fairly
simple device that stores and releases
electrical energy. They can be as small
as a thumbnail or as large as a soda
can. A typical UPS contains a dozen or
more of different types and sizes. Like
batteries, capacitors degrade over time.
There may not be visible effects upon
immediate failure, but one failure will
leave other capacitors to work harder
and shorten lifespan.
The large UPS battery handbook
Filters: Because dust may block
air filters and cause a UPS to shut
down due to overheating, they must
be inspected every month. Replacing
filters is an inexpensive component of
an effective UPS maintenance plan.
Fans: They may slow down or stall
as they age, and a resulting over
temperature condition will shut down
the UPS unexpectedly. Watch for fan
fail alarms every week, and plan for
replacement at the 8-10 year mark
at the latest.
2. Lithium-ion
Battery arrangement and power
In most UPSs, you don’t use just one cell at a time. They’re normally
grouped together serially to form higher voltages, or in parallel to
form higher currents. In a serial arrangement, the voltages add up.
In a parallel arrangement, the currents add up.
However, batteries are not quite
as linear as the two graphics to
the right depict. For example,
all batteries have a maximum
current they can produce; a
500 milliamp-hour battery can’t
produce 30,000 milliamps for
one second, because there’s no
way for its chemical reactions
to happen that quickly. It is
also important to realize that at
higher current levels, batteries
can produce a lot of heat, which
wastes some of their power.
Like all batteries, UPS batteries
are electrochemical devices. A
UPS uses a lead-acid storage
battery in which the electrodes
are grids of lead containing
lead oxides that change in
composition during charging and
discharging, and the electrolyte
is dilute sulfuric acid. In other
words, they contain components
that react with each other to
create DC electrical current.
These components are:
• E
lectrolyte: The medium
that provides the ion
transport mechanism
between the positive and
negative electrodes of a
cell, immobilized in VRLA
batteries, and in liquid form
in flooded-cell batteries
• G
rid: A perforated or
corrugated lead or lead alloy
plate used as a conductor and
support for the active material
• A
node: The terminal where
the current flows in
• C
athode: The terminal
where the current flows out
• V
alve (used in VRLA
batteries): Used to vent the
build-up of gas that goes
beyond pre-determined levels
• S
eparator: A device used
for the physical separation
and electrical isolation of
electrodes of opposing
• J
ar: The container holding the
battery components
Replacement lead acid batteries
for data room battery cabinets
Connecting in series [double voltage, same capacity (ah)]
+ -
+ -
Connecting in parallel [same voltage, double capacity (ah)]
Series connection
Parallel connection
Connecting of the positive terminal
of a cell/battery to the negative
terminal of the next cell/battery
increases the voltage of the battery
network while keeping the capacity
Connecting all the positive or
negative poles of several batteries
increases the capacity of a battery
network while maintaining a
constant voltage.
The large UPS battery handbook
Battery facts
Four factors that affect battery life
Batteries have limited life, usually showing a slow degradation of
capacity until they reach 80 percent of their initial rating, followed
by a comparatively rapid failure. Regardless of how or where
a UPS is deployed, and what size it is, there are four primary
factors that affect battery life: ambient temperature, battery
chemistry, cycling and service.
1. Ambient temperature
The rated capacity of a battery is based on an ambient
temperature of 25°C (77°F). It’s important to realize that any
variation from this operating temperature can alter the battery’s
performance and shorten its expected life. To help determine
battery life in relation to temperature, remember that for every
8.3°C (15°F) average annual temperature above 25°C (77°F), the
life of the battery is reduced by 50 percent.
UPS batteries are electrochemical devices whose ability to store
and deliver power slowly decreases over time. Even if you follow
all the guidelines for proper storage, usage and maintenance,
batteries still require replacement after a certain period of time.
3. Cycling
During a utility power failure, a UPS operates on battery power.
Once utility power is restored, or a switch to generator power is
complete, the battery is recharged for future use. This is called
a discharge cycle. At installation, the battery is at 100 percent of
rated capacity. Each discharge and subsequent recharge reduces
its relative capacity by a small percentage, albeit a much smaller
percentage for lithium-ion chemistry. The length of the discharge
cycle determines the reduction in battery capacity.
4. Maintenance
Battery service and maintenance are critical to UPS reliability. A
gradual decrease in battery life can be monitored and evaluated
through voltage checks, load testing or monitoring. Periodic
preventive maintenance extends battery string life by preventing
loose connections, removing corrosion and identifying bad
batteries before they can affect the rest of the string.
140 ºF
60 ºC
Average Annual Temperature
Optimum operating temperature for a VRLA and lithium-ion
battery is 25°C (77°F). High ambient temperature allows
unnecessary large quantities of charge current to flow which
results in a shorter service life.
Even though sealed batteries are sometimes referred to as
maintenance-free, they still require scheduled maintenance and
service. Maintenance-free simply refers to the fact that they don’t
require water to be added regularly.
Without regular maintenance, your UPS battery may experience
heat-generating resistance at the terminals, or inside the jar
improper loading, reduced protection and premature failure. With
proper maintenance, the end of battery life can be accurately
estimated and replacements scheduled without unexpected
downtime or loss of backup power.
What can go wrong with batteries?
Plate separation
Repeated cycling (charging and discharging),
damage during handling and shipping, and
Grid corrosion
Normal aging, operating in an acidic environment
and high temperatures
Internal short circuit
Heat (plates expand causing shorts), separator
failure, handling and shipping, and grid corrosion
External short circuit
Human error (shorting terminals) and leaks
Sulfation of plates
Sitting discharged for an extended period, not on
charge or being undercharged, such as battery shelf
life being exceeded past manufacturer’s guidelines
Excessive gassing
Often due to high temperatures or overcharging;
electrolyte volume is decreased
Drying out
Excessive gassing, high temperatures or
overcharging, resulting in too little electrolyte for
battery to function and provide full backup time
The large UPS battery handbook
Battery life: design life vs. actual life
Determining battery life can be a tricky business. It’s often
promoted based on design life, defined as how long the
battery can be expected to perform under ideal conditions.
Estimating actual battery life relies on taking into
consideration the four factors discussed on this page
that can affect it.
Battery Facts
Lead-acid or lithium-ion batteries, can only undergo a maximum
number of discharge/recharge cycles before the chemistry is
depleted, but lithium-ion cycle count is typically 10X that of lead
acid. Once the chemistry is depleted, the cells fail and the battery
must be replaced.
Relative Life
2. Battery chemistry
Battery disposal
Batteries that are replaced can still
contain a significant amount of hazardous
waste, including the electrolyte and lead.
Therefore, you must comply with EPA
guidelines for the disposal of all UPS
batteries. There are essentially two main
categories of disposal, one for spent
batteries and another for spills. The primary
ways to handle these two categories are:
Spent batteries
Send to secondary lead smelter for
recycling. For lithium-ion, return to original
vendor or an authorized 3rd party recycler
equipped to handle lithium batteries.
Spilled batteries
Battery Facts
Place neutralized leaked material into
sealed containers and dispose of as
hazardous waste, as applicable. Large
water-diluted spills, after neutralization
and testing, should be managed in
accordance with approved local, state and
federal requirements. Consult your state
environmental agency and/or the EPA.
An effective UPS battery maintenance
program must include regular inspections,
adjustments and testing, with thorough
records kept of all readings. Trained
technicians should:
One of the most successful recycling
efforts in the world is for lead-acid
batteries. According to Battery Council
International, more than 96 percent of
lead-acid batteries were recycled between
1997 and 2001. Many states require leadacid batteries be recycled, and several
options exist to dispose of used batteries,
• Inspect batteries and racks or cabinets
for signs of corrosion
vertical return alignment leakage
• M
easure and record the float voltage
and current of the
entire bank
• If you’re engaged with Eaton on a
battery upgrade or replacement, we’ll
take your old batteries and recycle them
for you
• R
ecord the terminal voltage of selected
• If you participate in Eaton’s UPSgrade
program, we take the old UPS and
recycle it. Visit for
• S
ome automotive stores accept batteries
for recycling
• M
any municipalities have dump or
recycling locations that will accept
batteries for recycling. When disposing
of batteries in this manner, be sure to
get a dated receipt clearly detailing what
batteries were dropped off, including
quantities with the recycler’s full name,
address and phone noted in the unlikely
event you get audited.
The large UPS battery handbook
• C
heck the electrolyte level in each cell,
if visible
• C
heck voltage balance and internal
temperature of lithium-ion cells
• Log the ambient temperature
• C
heck your local phone book for a local
recycler, or search for a recycler at
Quantifying the combined effect of
the four factors that affect battery life
discussed in the previous page is difficult.
You need a way to determine when a
battery is near the end of its useful life
so you can replace it while it still works,
before the critical load is left unprotected.
The only sure way to determine battery
capacity is to perform a battery rundown test. The module is taken off line,
connected to a load bank and operated
at rated power until the specified runtime
elapses or the unit shuts down due to low
battery voltage. If battery capacity is less
than 80 percent of its rated capacity, the
battery should be replaced.
Thermal scanning of battery connections
during the battery run-down test identifies
loose connections. This test gives you
the chance to see the battery during
an extended, high-current discharge.
Scanning should take place during
discharge and recharge cycles.
Battery maintenance
for extended life
• C
ompare data collected to previous
maintenance inspections to accurately
identify issues
Lithium-ion recycling
Lithium-ion batteries contain no toxic
materials, but should be recycled or
re-used, i.e. redeployed in solar, home
backup, or refurb automotive use.
Spot replacement of batteries
Batteries in series are similar to a string
of holiday lights. When one unit fails, the
entire string no longer works. When a
battery or group of batteries connected in
a series ceases to work, not only is the
battery string no longer functional, but it
can be difficult to determine which battery
has failed.
The most effective way to combat this
potential problem is to “spot” replace bad
batteries that are less than three years
old. While the four factors affecting battery
life play a large role in determining when a
battery is vulnerable to failure, there’s no
precise way to ensure that battery failure
can be predicted. The only way to identify
bad batteries early enough for spot
replacement is through continuous battery
monitoring and scheduled maintenance.
Spot replace bad VRLA batteries that are
less than three years old and replace the
whole string between the fourth and fifth
year (10th year for lithium-ion).
Used batteries: good for the
Which commonly used product has the
highest rate of recyclability? Paper? Only
73 percent of paper is recycled for reuse.
Aluminum at 54 percent and glass at
25 percent also fall short of the leader.
More than 96 percent of all battery lead is
recycled. Lead-acid batteries top the list of
most highly recycled consumer product.
The processes for lead-acid battery
recycling support agriculture needs and
enhance energy conservation. Beyond the
successful reuse of nearly 100 percent of
the battery components, lead recycling
facilities harness radiant heat from their
furnaces to offset traditional heating costs.
Residual sulfur trapped during recycling is
processed into fertilizer. Even the plastic
casings are crushed into pellets and are
used to manufacture new battery covers
and cases.
Recycling lead is also more energy
efficient than smelting or mining new
lead. The recycled lead can be refined into
new alloy repeatedly, giving it unmatched
sustainability and cost stability—a trait
unlike most raw materials.
Lithium batteries from a UPS are highly
likely to have a ‘second life’ in a solar
or electric vehicle application, before
ultimately being recycled. Contact the
battery vendor to see if this is
Battery safety
Handling and storage
The materials in batteries make them volatile and therefore
potentially hazardous. Performing regular periodic maintenance
on your UPS batteries can go a long way in preventing unsafe
situations before they occur.
Sulfuric acid is very combustible and contact with organic
materials may cause fire and explosion. It also reacts violently
with strong reducing agents, metals, sulfur trioxide gas, strong
oxidizers and water. Contact with metals may produce toxic
sulfur dioxide fumes and may release flammable hydrogen gas.
For lead compounds, avoid contact with strong acids, bases,
halides, halogenates, potassium nitrate, permanganate,
peroxides, nascent hydrogen and reducing agents. Lithium-ion
batteries actually contain no toxic substances, and pose no
hazard in normal handling. If a battery case is broken, consult
the vendor’s Material Safety Data Sheet (MSDS) for appropriate
action. Different lithium-ion battery models use a variety of
different chemical components, and safety procedures will vary.
You should always refer to the material safety data sheet for
specific precautionary measures. Primary steps for safe handling
and use are noted below.
Store batteries in cool, dry, well-ventilated areas with impervious
surfaces and adequate containment in the event of spills.
Batteries should also be stored under a roof for protection against
adverse weather conditions. Separate them from incompatible
materials. Store and handle only in areas with adequate water
supply and spill control. Avoid damage to containers. Keep away
from fire, sparks and heat.
State and local governments may have regulations concerning
how and where your UPS batteries are installed, usually
depending on the amount of electrolyte the batteries contain.
Flooded-cell batteries require special ventilation because of the
amount of hydrogen they emit and their liquid electrolyte. They
are usually stored away from the load and other equipment.
VRLA batteries are much less hazardous due to their immobilized
electrolyte, so they’re often not subject to the more stringent
regulations covering flooded-cell batteries and are often located in
the data center or near the protected load. Lithium-ion batteries
may be stored and handled in the same way as VRLA batteries.
Note that shipping procedures must comply with UN Class 9
requirements for lithium batteries.
Spills or leaks (for lead acid batteries)
Stop the flow of materials and contain/absorb small spills with
dry sand, earth or vermiculite. Don’t use combustible materials.
If possible, carefully neutralize spilled electrolyte with soda
ash, sodium bicarbonate or lime. Wear acid-resistant clothing,
boots and gloves, and a face shield. Do not allow discharge of
un-neutralized acid to get to the sewer.
Battery spill trays are designed to contain and absorb
leaking batteries
The large UPS battery handbook
Battery Facts
Appropriate personal protective equipment is essential when working on batteries or any UPS equipment
Battery FAQ
1. What is the “end of useful life”?
The IEEE defines “end of useful life” for a UPS battery as being
the point when it can no longer supply 80 percent of its rated
capacity in ampere-hours. When your battery reaches 80 percent
of its rated capacity, the aging process accelerates and the
battery should be replaced.
2. How can I ensure that my UPS batteries are maintained
and serviced properly?
With proper maintenance, battery life can be predicted and
replacements scheduled without interrupting your operations.
These are IEEE and OEM recommendations for general
• Comprehensive maintenance programs with regular inspections
• Re-torque all connections, as required
7. Our facility was damaged by a flood and our batteries were
partially submerged in water. What should we do?
The first concern in this situation is safety. Containing any
contamination is critical to preventing hazards to workers and the
8. My UPS has been in storage for over a year. Are the
batteries still good?
As batteries sit unused, with no charging regimen, their battery
life will decrease. On average batteries loose 3% of capacity
for every 30 days they sit uncharged due to the self-discharge
characteristics of lead-acid batteries. It is imperative that they
are charged periodically during storage according to the battery
manufacturer’s guidelines for temperature, charge duration and
resting period or permanent loss of capacity will occur.
9. What is thermal runaway?
• Load testing
• Cleaning the battery area, as required
3. Do I have to replace my UPS batteries with the same brand
of batteries?
Eaton recommends that if you use brand X and need to replace
one or two batteries in the string, you should use the same brand
because it will have the same characteristics. If you need to
replace the whole battery system, then you can change brands
with fewer risks.
Thermal runaway occurs when the heat generated in a leadacid cell exceeds its ability to dissipate it, which can lead to an
explosion, especially in sealed cells. The heat generated in the
cell may occur without any warning signs and may be caused
by overcharging, excessive charging, internal physical damage,
internal short circuit or a hot environment. Note that for lithiumion batteries the shelf life is typically two years at 25°C (75°F),
and one year at 60°C (140°F).
4. Are maintenance-free batteries maintenance free?
Battery FAQ
Though sealed batteries are sometimes referred to as
maintenance-free, they still require scheduled maintenance
and service. The term maintenance-free refers to the fact that
they don’t require fluid. Preventive maintenance is the key to
maximizing your UPS battery service life.
Thermal runaway
5. What about battery disposal?
It’s imperative that your service technicians adhere to EPA
guidelines for the disposal of all UPS batteries. Remember,
it’s the owner’s responsibility to make sure these guidelines
are followed.
Thermal runaway effects
on adjacent battery
6. Is there any difference between the batteries used by
smaller UPSs, from 250 VA to 3 kVA, and the ones used by
larger UPSs?
While basic battery technology, and the risks to battery life,
remain the same regardless of UPS size, there are some inherent
differences between small and large applications. Smaller UPSs
typically have only one VRLA battery that supports the load and
needs maintenance. As systems get larger, increasing battery
capacity to support the load gets more complicated. Larger
systems may require multiple strings of batteries, introducing
complexity to battery maintenance and support. Individual
batteries must be monitored to prevent a single bad battery from
taking down an entire string and putting the load at risk. Also, as
systems get larger, flooded-cell batteries become more common.
The differences in battery maintenance between VRLA and floodcell batteries discussed earlier apply.
The large UPS battery handbook
10. Is it safe to transport sealed batteries?
VRLA batteries marked as “non-spillable” are safe and
approved for all transportation methods as long as the container
is free of blemishes and local DOT regulations are followed.
However lithium-ion battery shipments are governed under UN
Class 9 requirements and designated procedures.
11. What is the difference between hot-swappable and
user-replaceable batteries?
Hot-swappable batteries can be changed out while the UPS is
running. User-replaceable batteries are usually found in smaller
UPSs and require no special tools or training to replace. Batteries
can be both hot-swappable and user-replaceable. Please check
your user’s guide for details on your UPS batteries.
12. How is battery runtime affected if I reduce the load on
the UPS?
The battery runtime will increase if the load is reduced. As a
general rule, if you reduce the load by half, you triple the runtime.
13. If I add more batteries to a UPS can I add more load?
Adding more batteries to a UPS can increase the battery runtime
to support the load, but it doesn’t increase the UPS capacity.
Be sure your UPS is adequately sized for your load, then add
batteries to fit your runtime needs.
14. What is the average lifespan of UPS batteries?
The standard service lifespan for VRLA batteries is three to five
years; lithium-ion, 10 years, and for flooded-cell batteries it’s
up to 20 years. However, expected life can vary greatly due to
environmental conditions, number and depth of discharge cycles,
and adequate maintenance. Having a regular schedule of battery
maintenance and monitoring will ensure you know when your
batteries are reaching their end-of-life.
15. Why are batteries disconnected on small, single-phase
UPSs when they’re shipped?
This is so that they’re in compliance with Department of
Transportation regulations.
16. If I have the serial number from the Eaton UPS or battery
cabinet, can I find out how old the batteries are?
17. Will Eaton replace batteries for other manufacturers’
Yes. Eaton batteries works on nearly all other manufacturers’
UPSs. In addition, we have extensive knowledge of Best Power,
Deltec, IPM and Exide Electronics models because these product
lines were purchased by Eaton.
18. What are the risks associated with a lack of battery
The primary risks of improperly maintained batteries are: load
loss, fire, property damage and personal injury.
19. Who are the major battery manufacturers?
There are many battery manufacturers, but the major ones are:
C&D, Enersys, CSB, Samsung, Yuasa, Panasonic and GS – to
name a few.
20. If I have one bad battery, should I only replace that faulty
battery, or replace the entire battery string?
Having one faulty battery doesn’t mean you have to replace the
entire battery string, which can be very costly. You can replace
the bad battery with a fully charged unit but you also need to
test the health of the entire string to the cell level to identify if
additional strain from the faulty battery damaged other units.
The large UPS battery handbook
21. Why do batteries fail?
Batteries can fail for a multitude of reasons, but common
reasons are:
• High or uneven temperatures
• Inaccurate float charge voltage
• Loose inter-cell links or connections
• Loss of electrolyte due to drying out or damaged case
• Lack of maintenance, aging
22. What is the importance of power density when talking
about batteries?
Batteries differ markedly in the number of watts per cell. A higher
density battery provides more runtime for the footprint. You may
even find you can reach your runtime requirements with fewer
battery cabinets, which reduces upfront and lifetime costs of
battery preventive maintenance.
23. How is battery performance generally measured?
Batteries are generally rated for 100+ discharges and recharges,
but many show a marked decline in charging capacity after as
few as 10 discharges. The exception is lithium-ion batteries which
are typically rated for up to 2000 discharges over their service
life. The lower the charge the battery can accept, the less runtime
it can deliver. Look for batteries with a high-rate design that
sustains stable performance for a long service term.
24. When are 10-year design life SVRLA batteries typically
replaced in standard UPS applications?
UPS battery life depends on a number of factors, including
operating temperature, number and duration of discharges,
and if regular preventive maintenance is performed. While
it’s theoretically possible for SVRLA batteries to last 10 years
under optimum conditions, the industry typically recommends
full replacement between years four and five for reliability
purposes in UPS applications. Note that lithium-ion battery typical
replacement interval is 10 years.
25. How can I determine the age of a battery?
Batteries shipped on or after January 1, 2000 have a four-digit
shipping code with the first two digits as the year and the
following two as the month in which the battery was shipped
from the factory. For example, a code of 1710 would be
interpreted as 2017, October.
Battery FAQ
Every Eaton battery has a manufacturer date code that indicates
when it was made. The battery or battery cabinet will also feature
a sticker for each time the batteries have been recharged while
in storage. Stored batteries require charging periodically during
storage to avoid loss of capacity. Recharging stored batteries
doesn’t affect battery warranty as long as it does not exceed a
battery manufacturer’s guidelines for the number of recharges
before a battery is put into service.
All it takes is one bad battery to ruin an entire string and bring
your systems down during a power outage or other interruption.
There is no precise way to predict battery failure. Continuous
battery monitoring and scheduled maintenance are the most
effective way to identify bad batteries early enough for spot
Eaton battery
products and
Eaton’s line of premium batteries for Eaton three-phase UPS models is backed by a service network of
trained and qualified battery service technicians
Eaton battery services overview
Battery preventive maintenance
Eaton provides a comprehensive set of services for batteries.
Preventive maintenance ensures uptime and extends battery life
by eliminating problems before they happen. Whether a battery
fails from defect or deterioration, the best time to find out is
during preventive maintenance service, not when the battery is
called on to support the critical load. Eaton will custom design a
preventive maintenance package that’s best for you, including the
following features:
• B
attery preventive maintenance/onsite inspection:
technicians test, inspect, clean and analyze battery
performance and provide a detailed report that includes any
recommendations for corrective action
• E
aton battery: includes options to replace individual batteries
or the entire string
• Eaton CellWatch: battery monitoring
• 1
0 percent partial replacement coverage: coverage for parts
and labor for a bad battery up to 10 percent of the total count
of batteries installed
• C
ustomer Support Center: complete 24x7 command center
for all Eaton services
• C
omprehensive maintenance schedule for your VRLA
or flooded-cell batteries per IEEE guidelines
• Measure cell voltage levels
• Visual inspection for leaks or bad cells
• Spot check for connection torques
• Load testing
• Inspection of battery environment
Products & Services
• Detailed hard copy of battery test and inspection results
For more information on Eaton batteries, please visit
• Written inspection report and recommendation
This also includes spot replacement of batteries. When we
identify one or two bad batteries, we replace them immediately
onsite if the Eaton technician has replacements available at the
time of the preventive maintenance regimen, or schedule prompt
replacement if batteries need to be ordered.
Eaton VRLA battery models available
Labor adder
Eaton 12V 34W battery
2-year parts/1-year labor
2-year parts/2-year labor
Eaton 12V 120W battery
2-year parts/1-year labor
2-year parts/2-year labor
Eaton 12V 200W battery
3-year parts/1-year labor
3-year parts/3-year labor
Eaton 12V 280W battery
3-year parts/1-year labor
3-year parts/3-year labor
Eaton 12V 330W battery
3-year parts/1-year labor
3-year parts/3-year labor
Eaton 12V 390W battery
3-year parts/1-year labor
3-year parts/3-year labor
Eaton 12V 540W battery
3-year parts/1-year labor
3-year parts/3-year labor
The large UPS battery handbook
Eaton batteries
Why Eaton batteries?
Eaton Cellwatch
As a part of our commitment to delivering
the highest reliability in power availability,
Eaton offers a line of premium batteries
for our three-phase UPS models.
Eaton batteries combine field-proven
performance and quality at competitive
pricing and are backed by our network
of trained battery customer service
Proven performance. Eaton batteries
have been thoroughly tested by our
engineering team and shown to adhere
to our stringent performance and quality
Eaton Cellwatch is an advanced battery
monitoring system for three-phase
UPSs. All information collected by
Eaton Cellwatch is gathered at a central
monitoring unit, where it’s analyzed on
Windows®-compatible software. The
system uses fiber-optic technology, which
is non-conducting and introduces no
electrical noise, so all readings are precise
and accurate.
Prior to using a battery in an Eaton
product, a thorough review of the
performance, manufacturing and design
data is conducted. The presence of
specific attributes of the design and
manufacturing process, important for UPS
battery use, is confirmed.
Following the review and assuming the
outcome is successful, a statistically
significant sample of the batteries is
obtained from the manufacturer. This
sample is required to have been built
from the manufacturer’s existing process
for that battery. A series of tests and
physical examinations are conducted on
this sample; including a set of discharges
using various loads to characterize the
performance of the battery, charge tests
and tests for float current stability at
normal to high-float voltages. Failures
or inconsistencies in performance are
investigated further and reviewed by
the manufacturer. In some cases, a teardown analysis is performed to identify
the cause of the problem. If the battery is
found acceptable and all open issues are
resolved, a limited series of discharges,
with recharge, are performed.
High-rate design. Charge after charge,
the batteries approved for the Eaton
brand sustained high runtime levels, while
performance of non-qualified batteries
dropped off markedly after only 10
Extended warranty coverage. Eaton
offers a full three years (excluding 34W
and 120W battery models which are two
years) of parts coverage with full (not prorated) replacement of any failed battery.
In the unlikely event a replacement
battery fails within the first year, Eaton
will send a technician on-site to install the
replacement battery at no charge. With
regional stocking locations, we can get
replacement batteries to you quickly.
Expert technical support. Eaton batteries
are backed by our service network of
trained and qualified battery service
engineers who are available to install
and maintain your batteries. Beyond the
warranty period, you can choose battery
monitoring services and maintenance
plans that take the guesswork and
administrative tasks out of battery
Easy installation. No special harnesses
are needed when these batteries are
installed with new UPSs. Harnesses are
readily available for legacy UPSs.
Eaton Cellwatch battery monitoring system monitors key
performance indicators for each individual battery to provide
adequate time to detect and replace a bad battery, mitigating
the risk of downtime
The large UPS battery handbook
Eaton Cellwatch provides continuous
monitoring of your batteries to allow you
to proactively identify and address battery
issues. This includes:
• M
onitoring of voltage, internal
resistance and temperature
• Immediate warning and specific battery
identification of deterioration and
imminent failure
• R
eduction of the possibility of damage
to entire battery string
• R
eplacement based on actual battery
condition, preventing costly premature
• M
inimum of 120 days of activity history,
enabling you to trend individual battery
and string performance
• C
ontinuous monitoring of string and
battery discharge currents ranging from
25A to 1000A
• Programmable alarm functions
• Remote monitoring capabilities (optional)
• M
ay be used to detect thermal runaway
in advance
Thermal runaway
Thermal runaway is the most dangerous
and potentially catastrophic situation
involving lead-acid batteries. It occurs
when the heat generated in a lead-acid
cell exceeds its ability to dissipate it,
which can lead to an explosion, especially
in sealed cells. The heat generated in
the cell may occur without any warning
signs and may be caused by overcharging,
excessive charging, internal physical
damage, internal short circuit or a hot
By monitoring every jar or cell in the
battery system for signs of failure, Eaton
Cellwatch is uniquely suited to find the
causes and symptoms of thermal runaway
before damage occurs.
Products & Services
This intense and thorough quality testing
ensures that Eaton batteries are ready for
peak performance at their stated capacity
as soon as they’re deployed.
High power density. An optimized design
delivers more watts per cell, more power
for the volume than other batteries on
the market. As a result, Eaton batteries
provide more runtime for the footprint,
more runtime per dollar.
Extending battery service life
Eaton PredictPulse Insight
Eaton’s ABM technology uses a unique three-stage charging
technique that significantly extends battery service life
and optimizes recharge time compared to traditional trickle
charging. An integrated battery management system tests and
monitors battery health and remaining lifetime and provides
advance notification to guide preventive maintenance. Optional
temperature-compensated charging monitors temperature
changes and adjusts the charge rate accordingly to properly
charge the battery and greatly extend battery life. A variable
battery bus accommodates 384V to 480V configurations, so
the battery capacity can be matched to your exact runtime
requirements—either a specific runtime, an extension to existing
battery runtime or legacy battery installations. With remote
monitoring of the UPS and battery system, Eaton is able to
respond to alarms and real-time battery data to avert potential
battery problems. Note: ABM is not applicable for flooded-cell or
lithium-ion systems.
Remote monitoring and management is like a second set
of eyes that is keeping tabs on your equipment 24 hours a day,
7 days a week and will notify you of any issues. PredictPulse™
Insight is a monitoring and management service that collects
and analyzes data from connected power infrastructure devices,
providing us with the insight needed to make recommendations
and take action on your behalf. Once activated, managed
devices send parametric data to Eaton’s monitoring center every
15 minutes. We compare current and historical performance
data against specified parameters to determine if anything is
out of the ordinary. At the same time, the data appears on
your PredictPulse dashboard and alarms in the mobile app. If
something is amiss, we’ll notify you of the alarm and how we
recommend addressing it.
Battery Backup Time
(in minutes and seconds)
UPS with ABM
UPS with Float Charge
UPS with Lithium-Ion
This means less time spent managing IT equipment, reduced
risk, access to real-time status information and expedited
repairs. You’ll also receive a report each month summarizing
the past 30 days of status, performance, alarms and upcoming
service needs.
80% I
90 100 110 120
Battery Age
(in months)
Although batteries are sold with a variety of published
life spans, the fact is, some demonstrate a useful life
of as little as three to five years. Eaton’s exclusive
ABM technology significantly increases the life of
VRLA UPS batteries.
The Eaton Customer Monitoring Center stands ready to assist 24x7
Products & Services
Customer Monitoring Center
Eaton’s global 24x7 service operations command center is a hardened, secure facility
for all UPS product service scheduling, technical support and remote monitoring support.
Customer support staff are
trained to qualify and prioritize all
incoming calls using defined
processes, complemented by a
knowledge database, with tech
support and domain experts at
their disposal 24x7.
The benefits of the Customer
Monitoring Center include:
• E
ases customer hassle of managing
battery health
• Increased reliability via remote
diagnostic and remote repair tools
delivered by Eaton product experts
• S
aves time for busy facility or IT
• E
xpedited service response to
critical UPS and battery alarms
(reduces risk and cost of downtime)
• 2
4x7 notification of critical alarms
or trends
The large UPS battery handbook
• E
nhanced internal self-monitoring
resources and capabilities
• M
onthly reports designed for both
technical and non-technical use
• D
evelopment of trending database
on both UPS and battery
Maintaining uptime,
even in the world’s
worst weather
The Mt. Washington
Observatory can’t have
any interruptions in
power, which is why
we have the Eaton
UPS. We’re collecting
data continuously, and
those types of
instruments do not like
interruptions in power.
It’s also holding
together our entire
IT infrastructure.
Cyrena-Marie Briedé, director of
summit operations
The Mt. Washington
Observatory (MWO) is a
private, non-profit scientific
and educational institution
dedicated to advancing the
understanding of the natural
systems that create the Earth’s
weather and climate. The
summit of Mt. Washington is
home to some of the most
dangerous and unpredictable
weather in the world, so MWO
maintains a mountaintop
station to conduct research,
oversee educational programs
and collect real-time data that
feeds into the National Weather
Service’s forecast models.
When an outage happens,
the 9355 immediately kicks
on to keep MWO’s systems
operating until its generator can
power up. Although this usually
takes just a matter of seconds,
without a highly reliable UPS
to bridge the gap, those
seconds could result in holes
in the organization’s 80-year
continuous weather history.
While the 9355 performed
flawlessly through the years,
by 2014, its batteries needed to
be replaced. The MWO IT team
reached out to Eaton to arrange
a battery replacement and get
the UPS on a service plan.
Discovering that MWO
had reduced its equipment
since the UPS was first
installed, Eaton’s service team
determined that 90 minutes
of runtime—rather than the
originally slotted 170 minutes—
would be more than sufficient
for the organization.
In winter, the Mt. Washington Observatory is an ice and snow palace, battered
by hurricane-force wind gusts
The large UPS battery handbook
The field technicians trekked to
the top of Mt. Washington with
four new strings of batteries for
the observatory. They safely
removed 32 trays of batteries
and two cabinets—about
3,840 pounds of materials.
This helped MWO significantly
consolidate its UPS solution,
saving valuable space at the
Eaton’s reliable service was
invaluable to the staff at
MWO. “We’re in an extreme
environment here…we have to
fix things on site and there’s no
hardware store just down the
street,” said an IT specialist
at MWO. “Even in the best
of conditions, we’re a difficult
place to get to. Eaton still
manages to provide service on
a regular basis and when we
need it.”
With a more compact UPS
solution, real-time system
updates and the addition of
an environmental monitoring
probe, MWO is in an excellent
position to preserve its 80-year
weather history and capture as
much data as possible during
extreme weather. Watch this
video for the full story:
Products & Services
At an elevation of 6,288 feet,
the observatory is prone to
direct lightning strikes; during
winter, conditions become even
more treacherous with ice,
snow and blistering hurricaneforce wind gusts—all of which
can knock out electricity.
Years ago, MWO deployed a 15
kVA Eaton 9355 uninterruptible
power system (UPS) with more
than 170 minutes of runtime
to help ensure that even when
the most extreme weather hits,
the organization can continue
gathering and storing vital data.
Battery glossary
Absorbed electrolyte –
Electrolyte that’s been
immobilized in an absorbent
Absorbed electrolyte cell – A
cell, usually a valve-regulated
sealed lead-acid type, which
utilizes absorbed electrolyte.
Absorged glass mat (AGM)
battery – Designed with
electrolytes held in thin glass
fibers woven into a mat to
increase surface area enough
to hold sufficient electrolyte on
the cells for their lifetime. AGM
batteries are also known as
“starved electrolyte” or “dry”
because the fiberglass mat has
no excess fluid.
Accessories – The components
required to complete the
battery installation, including
connectors, flame-arrestor
vents, cell numbers and
Activation charge – The
process of making a drycharged cell functional by
introducing electrolyte and
Active material – The material
in the electrodes (plates) of
the cell that reacts chemically
to produce electric energy
when the cell discharges,
which is restored to its original
composition during the charge
Actual capacity – The total
number of ampere-hours that
could be withdrawn from a
cell based on a specific set of
operating conditions (including
initial state-of-charge, discharge
rate, initial cell temperature
and end voltage) and the age
of the cell.
Ambient temperature – The
average temperature of the
surrounding air that comes into
contact with the battery.
Anode – The electrode in an
electrochemical cell where
oxidation takes place. During
discharge, the negative
electrode of the cell is the
anode. During charge, this
reverses and the positive
electrode of the cell is the
As found (condition) – A term
used to inform the person
performing a capacity test that
the battery should be tested
without performing certain
checks, so the test results will
reflect the effect (good or bad)
of the maintenance practice
followed for the installation.
Average temperature – The
average of the individual cell
temperatures of all the cells in
a battery.
The large UPS battery handbook
Average voltage – The
average of the individual
cell voltages of all the cells
in a battery. This term may
be applied to a variety of
conditions, including average
float voltage and average
discharge voltage.
Battery – Two or more cells
connected together electrically.
Cells may be connected in
series or parallel, or both, to
provide the required operating
voltage and current levels.
Battery charger – An
apparatus that restores the
charge of a secondary battery.
Also known as a rectifier.
Battery duty cycle – The load
a battery is expected to supply
for a specified time period.
Battery management system
– Required for lithium-ion
systems, this monitors and
controls cell balance and can
take action to disconnect
a failing battery string
Battery monitor – A piece of
equipment used to monitor
various parameters of a
battery, such as individual cell
voltage, battery voltage and
Battery nominal voltage –
The nominal voltage of one cell
multiplied by the number of
cells in the battery.
Battery rack – A structure
used to support a group of
cells. The most common
rack material is steel with a
corrosion-resistant coating.
Boost charge – An overcharge
of any length.
Cathode – The electrode
in an electrochemical cell
where reduction takes place.
During discharge, the positive
electrode of the cell is the
cathode. During charge, this
reverses and the negative
electrode of the cell is the
Carbonization – A condition
where the electrolyte becomes
contaminated with potassium
carbonate to a point where it
influences cell performance.
Capacity – The ampere-hour
capacity assigned to a cell by
the manufacturer for a given
discharge time, at a specified
electrolyte temperature and
specific gravity to a given endof-discharge voltage.
Cell – The basic electrochemical
unit, characterized by an anode
and cathode, used to receive,
store and deliver electrical
Cell temperature – The
temperature at which a cell
is operating. In the U.S., the
reference for cell temperature
is 25°C (77°F).
Charge – The conversion of
electrical energy into chemical
energy within a secondary cell.
Closed-circuit voltage – The
voltage of a cell when it’s
Constant current charge –
A charge in which the
current output of the charge
is maintained at a constant
value. Sometimes this may be
accomplished using two-rate
Constant voltage charge – A
charge in which the potential
voltage at the output terminals
of the battery charger is
maintained at a constant value.
Flooded-cell – A cell design
that’s characterized by an
excess of free electrolyte,
and in which the products of
electrolytes, such as gasses,
and evaporation, can freely exit
the cell through a vent. (Also
see wet-cell.)
Electrode – The site at which
the electrochemical reaction
takes place.
Freshening charge – A charge
given to a battery following
non-use or storage.
Electrolyte – A conducting
medium in which the flow of
electric current takes place.
Full-float operation –
Operation of a DC system with
the battery, battery charger and
load connected in parallel, with
the battery charger supplying
the normal DC load plus any
self-discharge or charging
current, or both, required by
the battery.
Element – The positive and
negative plate groups with
separators assembled for one
End cell – A cell that can be
added to or removed from a
battery circuit to adjust battery
Cycle – A discharge and
subsequent charge of a cell.
End voltage – The cell voltage
at which the discharge is
Density – The weight of a
given volume of electrolyte at
a specified temperature.
Energy density – The ratio of
the available energy from a cell
to its volume or weight.
Depth of discharge – The
ampere-hours removed
from a fully charged battery,
expressed as a percentage
of its rated capacity at the
applicable discharge rate.
Flame-arrestor vent – A cellventing device that prevents
the propagation of an external
flame into the cell.
Discharge – The conversion of
chemical energy into electrical
energy within a cell.
Flame-retardant material – A
material capable of limiting the
propagation of a fire beyond
the area of influence of the
energy source that initiated it.
Discharge rate – The rate in
amperes at which current is
delivered by the battery.
Float current – The current
drawn by a cell that’s being
float charged.
Dry-charged cell – A cell
that’s been assembled with
its plates dry, and in a charged
state, ready to be activated by
the addition of electrolyte...
allowing easier shipping and
Float voltage – The voltage
applied during full-float
The large UPS battery handbook
Fully-charged – The condition
that exists following a longterm constant current charge.
Gassing – Evolution of gas by
one or more of the plates in a
cell, resulting from electrolysis
of water into hydrogen and
oxygen within a cell during
charging, overcharging or local
action. Lithium-ion batteries, if
overcharged, may emit small
amounts of gasses (CO2, CO,
Phosphorus Oxide). See the
vendor’s MSDS for safety
Gelled electrolyte –
Electrolyte that’s been
immobilized by the addition of
a gelling agent.
Gelled electrolyte cell – A
cell, usually lead-acid or VRLA,
that uses gelled electrolyte.
General purpose cell – A
cell designed to supply a duty
cycle requiring a high current
for a short period of time
followed by a low current for
a long period of time. This
term is used in the U.S. for
cells designed for switchgear
tripping, generating stations
and control applications.
Grid – A framework for a
plate in a cell that supports or
retains the active material and
conducts the electric current.
High level line – A line on the
side of a jar that shows the
maximum level of electrolyte
that should be present in a
High performance cell – A
cell designed to supply a duty
cycle requiring a high current
for a short period of time.
Hit – Indicates that a standby
battery has been discharged.
Hit counter – A device used
to record the number of
discharges experienced by a
Hydration (lead-acid cell) –
A condition caused by
discharging a cell, and failing to
recharge it in a timely manner.
Immobilized electrolyte –
Electrolyte that’s retained by a
gel or absorbent mat.
Initial charge – The charge
given to a new battery before
placing it in service.
Initial voltage – The closedcircuit voltage at the beginning
of a discharge.
Integrity test – A test used
to detect conduction path
Inter-cell connection
resistance – The total electrical
resistance of the connection
between the terminals of
two cells that are electrically
connected to each other.
Efficiency – The
electrochemical efficiency,
expressed as a percent, of
the ratio of the ampere-hour
output of the battery, to the
ampere-hour input required
to restore the initial state of
Inter-cell connector – An
electrical conductor used to
connect adjacent cells on the
same rack.
Inter-cell connector safety
cover – An insulated cover
placed over the inter-cell
connector and post, used to
prevent accidental contact by
personnel or accidental short
circuiting of the cell.
Inter-rack connector – An
electrical conductor used to
connect cells on two separate
racks, most often insulated
copper wire.
Internal impedance – The
resistance of a cell to an
alternating current of a specific
Internal resistance – The
resistance of a cell to an
electric current within a cell.
Internal voltage drop – The
product of the current passing
through the cell.
Jar – The container that
holds a cell or group of cells.
Common jar materials include
thermoplastics, but hard
rubber is sometimes used as
well and nickel-cadmium cells
may be in steel containers.
Jars for flooded lead-acid cells
are normally transparent to
allow inspection of the plate
and sediment.
Jar-to-cover seal – The seal
at the interface of the jar and
Lead-acid cell – A secondary
cell in which the electrolyte
is a solution of sulfuric acid in
water. Lead-acid cells include
pure lead cells and lead alloy
cells such as lead-antimony,
lead-calcium and leadselenium.
Level line – A line or set of
lines on the sides of the jar
used to indicate the cell’s
minimum or maximum of
electrolyte level.
Lithium-ion cell – Lithiumion cells, made of lithium and
other metals and chemicals,
are lighter and more energy
dense than comparable lead
acid cells. They are typically
packaged in a ‘module’ that
contains enough cells to
attain the desired voltage
and current capability. Each
cell is comprised of metal
electrodes, separators, internal
fusing and vents, along with
a management circuit that
controls its balance of current
and voltage, ensuring overtemperature conditions do not
Local action – The internal
losses of a battery standing on
open-circuit or on float charge,
without considering any losses
incidental to any discharge.
Long duration cell – A cell
designed to supply a duty
cycle requiring a low current
for a long period of time.
Low level line – A line
on the side of a jar that
represents the minimum level
of electrolyte that should be
present in a cell.
Modified-plante plate – A
lead-alloy grid containing holes
into which pure lead corrugate
strips are placed.
Multi-cell container – A multicompartment container in
which each compartment may
contain an individual cell.
The large UPS battery handbook
Multi-cell unit – A multi-cell
container in which cells are
Negative plate – The
electrode to which current
flows from the external circuit
when the cell is discharging.
Negative terminal – The
terminal toward which positive
charge flows in the external
circuit, such as from the
positive terminal, when the cell
NiCad battery – A sealed
storage battery having a nickel
anode, a cadmium cathode,
and an alkaline electrolyte.
Nominal gravity – The specific
gravity of the electrolyte
selected for the determination
of the rated capacity of the cell
when it’s fully charged.
Open-circuit voltage – The
voltage of a cell with no
current flow in either direction
after the cell has had time to
Overcharge – The forcing of
current through a battery after
it’s been fully recharged.
Oxygen index – The minimum
concentration of oxygen,
expressed as volume percent,
in a mixture of oxygen
and nitrogen that will just
support flaming combustion
of a material initially at room
Oxygen recombination –
A process whereby oxygen
generated at the positive
electrode recombines with
hydrogen at the negative
electrode to convert to water.
Oxygen recombination
efficiency – A ratio of the
quantity of oxygen recombined
to the total amount of oxygen
Parallel – The interconnection
of cells in which all the like
terminals are connected.
Parallel strings – The
interconnection of two or
more strings in which the like
terminals of each string are
Pasted plate – A grid filled
with active material applied as
a paste.
Performance test – A
constant-current capacity test
made on a battery after being
placed in service to detect
any change in the capacity
determined by the acceptance
Pilot cell – A selected cell
whose condition is assumed
to indicate the condition of the
entire battery.
Plante plate – A pure lead
plate for a lead-acid cell in
which the active material is
formed directly from a lead
Plate – An assembly of active
materials on a supporting
framework grid, frame or
support strip. (Also called an
Pocket plate – A plate in which
the active material is held in
perforated metal pockets on a
support strip. Usually used for
nickel-cadmium cells.
Point (of specific gravity) –
One-thousandth of specific
gravity (SG).
Polarization – The change in
voltage at the terminals of a
cell when a specified current is
flowing into it.
Positive plate – The electrode
from which the current flows
to the external circuit when
the battery is discharging.
Positive terminal – The
terminal from which the
positive electric charge flows
through the external circuit to
the negative terminal when the
cell discharges.
Power density – The ratio of
the available power from a cell
to its volume or weight.
Rated capacity – The amperehour capacity assigned to a cell
by its manufacturer for a given
discharge time, at a specified
electrolyte temperature to a
given end-of-discharge voltage.
Recombination vent – A vent
in which most of the gasses
escaping from the cell are
catalytically recombined and
returned to the cell as water.
Reference electrode – A
special electrode that has
a reproducible potential
against which other electrode
potentials can be referred.
Retainer – Any material that
is used to prevent the loss
of active material from the
positive plate.
Reversal – A changing of the
normal polarity of a cell.
Rundown test – A partial
discharge test to a voltage
other than the system
designed and voltage.
Sealed, lead-acid (SLA)
battery – non-spillable,
maintenenace-free valve
regulated batteries designed
with vents that cannot usually
be removed.
Secondary cell – An
electrochemical cell that’s
capable of being discharged
and then recharged.
Secondary battery – Two
or more secondary cells
connected electrically.
Sediment – The active material
that separates from the battery
plates and falls to the bottom
of the jar.
Step rack – A rack in
which cells are placed at
different levels in a stepped
Self-discharge rate – The
amount of capacity reduction
occurring per unit of time in
a battery as a result of selfdischarge.
Strap – The component in a
cell where all the plates of like
polarity are joined.
Separator – An ionic
permeable, non-conductive
spacer used to prevent
metallic contact between
plates of opposite polarity
within a cell.
Series – The interconnection of
cells in such a manner that the
positive terminal of the first
is connected to the negative
terminal of the second and so
Service life – The period of
time during which a fully
charged battery is capable of
delivering at least a specified
percentage of its rated
capacity. For most lead-acid
battery designs this is 80%.
Shipping vent – The vent
placed in the cell for the
purpose of shipping it.
The large UPS battery handbook
String – A common way to
refer to a number of cells
connected in series to form a
battery system.
Sulphation (lead-acid cell) –
A state where the battery
has developed an abnormal
amount of sulphate and its
capacity is impaired which is
different from normal sulphate
that occurs during discharge.
Taper charge – A charge in
which both current and voltage
decrease over the recharge
Terminal – The part of a cell
to which the external circuit is
Tier rack – A rack in which
cells are placed directly above
each other at different levels.
Trickle charge – A charge
given to a battery with no
external load connected to it
to maintain it in a fully charged
Valve – A normally sealed
mechanism that allows for the
controlled escape of gasses
from within a cell.
Valve-regulated sealed
lead-acid cell – A cell that’s
sealed and fitted with a valve
opens to vent it whenever
the internal pressure exceeds
the external pressure by a set
Vent – A device that allows
the escape of gasses from
within a cell.
Voltage efficiency – A ratio
of the average voltage during
discharge to the average
voltage during recharge, under
specified conditions.
Voltage spread – A term used
to describe the difference
between the highest and
lowest individual cell voltage
readings in a battery.
Wet-cell – A cell design
that’s characterized by an
excess of free electrolyte,
and in which the products of
electrolytes, such as gasses,
and evaporation can freely exit
the cell through a vent. (Also
see flooded-cell.)
Thermal runaway – A
condition in which a cell
on charge or discharge will
destroy itself through internal
heat generation caused by high
overcharge or over-discharge
current or other abusive
State-of-charge – The actual
capacity of a cell, expressed as
a percent of its rated capacity,
that would be available if a
discharge were to occur.
Stationary battery – A
secondary battery designed
for service in a permanent
Specific gravity – The ratio of
the weight of a given volume
of electrolyte to the weight of
an equal volume of water at a
specified temperature.
Standby battery – A battery
designed to function only
when the normal source of
power fails.
For more information, visit
or call 1.800.356.5794
1000 Eaton Boulevard
Cleveland, OH 44122 USA
© 2017 Eaton Corporation
All Rights Reserved
Printed in USA
September 2017
Eaton, ABM and PredictPulse are registered
All other trademarks are property
of their respective owners.
Follow us on social media to get the
latest product and support information.
Was this manual useful for you? yes no
Thank you for your participation!

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Download PDF