Guide to VRLA Batteries - East Penn Manufacturing

Guide to VRLA Batteries - East Penn Manufacturing
Valve-Regulated Lead-Acid (VRLA):
Gelled Electrolyte (Gel) and Absorbed Glass Mat (AGM) Batteries
EAST PENN Expertise and American Workmanship
How it Works
Difference Between VRLA and Flooded
Ideal Applications
AGM Batteries
Gel Batteries
Similarities Between Gel & AGM
Differences Between Gel & AGM
Gel & AGM Battery Design Advantages
East Penn’s VRLA Features
and Benefits
East Penn’s Quality Assurance Checks
Valve-Regulated Lead-Acid or VRLA, including Gel and AGM
(Absorbed Glass Mat) battery designs, can be substituted in
virtually any flooded lead-acid battery application (in conjunction with well-regulated charging). Their unique features and
benefits deliver an ideal solution for many applications where
traditional flooded batteries would not deliver the best results.
For almost three decades, East Penn has been manufacturing valve-regulated batteries using tried and true technology
backed by more than 65 years experience. East Penn produces a complete line of Gel, AGM, and conventional
flooded products for hundreds of applications. This diverse
product offering enables East Penn to be objective as to the
advantages of each type of battery. East Penn’s VRLA (Gel
and AGM) products have the reputation of being the highest
quality VRLA batteries available.
How it works
A VRLA battery utilizes a one-way, pressure-relief valve
system to achieve a “recombinant” technology. This means
that the oxygen normally produced on the positive plate is
absorbed by the negative plate. This suppresses the production
of hydrogen at the negative plate. Water (H2O) is produced
instead, retaining the moisture within the battery. It never
needs watering, and should never be opened as this would
expose the battery to excess oxygen from the air. In addition to
damaging the battery, opening it also voids the warranty.
The difference between VRLA and traditional
flooded batteries
Flooded electrolyte batteries do not have special one-way,
pressure-relief valves, as they do not work on the recombination principle. Instead, flooded designs utilize a vent to
allow gas to escape. They contain liquid electrolyte that can
spill and cause corrosion if tipped or punctured. They
should not be used near sensitive electronic equipment.
They can only be installed “upright.” Flooded batteries lose
capacity and become permanently damaged if:
n Left in a discharged condition for any length of time
(due to sulfation). This is especially true of designs that
require water maintenance.
n Continually over-discharged (due to active material shedding). This is especially true of automotive starting types.
Ideal applications for VRLA batteries
Deep Cycle, Deep Discharge Applications
n Marine Trolling
n Electronics
n Sailboats
n Electric Vehicles
n Wheelchairs/Scooters
n Golf Cars
n Portable Power
n Floor Scrubbers
n Personnel Carriers
n Renewable Energy
(Solar, Wind)
n Village Power
Marine & RV
House Power
Commercial Deep
Cycle Applications
Standby and Emergency Backup Applications
n UPS (Uninterrupted
n Cable TV
Power Systems)
n Emergency Lighting
n Computer Backup
n Renewable Energy
(Solar, Wind)
n Frequency Regulation
Telephone Switching
Other Applications
Race or High
Performance Cars
Wet Environments
Diesel Starting
Vehicles with
Start-Stop Systems
On-Highway Trucking
Off-Road Vehicles
Marine & RV Starting
Cars and Light Trucks
with Accessories
Advantages of GEL and AGM battery designs
VRLA technology encompasses both gelled electrolyte or gel
batteries and absorbed glass mat or AGM batteries. Both types
are regulated by special one-way, pressure-relief valves and
have significant advantages over flooded lead-acid products.
Premium maintenance-free design
AGM (Absorbed Glass Mat) batteries
The electrolyte in AGM batteries is completely absorbed in
separators consisting of matted glass fibers. This causes them
to be spillproof, meaning they don’t leak acid like a flooded
design if tipped on their side. The glass mats in AGM batteries
are wrapped around the positive plate, which helps prevent
damage from vibration and extend cycling. The battery’s
groups are packed tightly in the case partitions also protecting its power producing components. AGM battery designs
can have over twice the cycle life of a conventional flooded
product in the right application.
Air transportable
The electrolyte in a Gel battery is permanently locked in a
highly viscous gelled state instead of the traditional liquid
form. Because there is no liquid-type electrolyte, it will not
leak out of the battery if tipped on its side. The thick, gelled
electrolyte and tightly packed groups also protect the battery’s power producing components. Gel battery designs
have a superior deep discharge resiliency and can deliver
over two to three times the cycle life of an AGM product in
the right applications.
Similarities between Gel
and AGM VRLA technology
Spillproof construction,
won’t leak if turned sideways
Minimizes terminal corrosion
Operates at severe angle or on side
(won’t leak or spill)
Low to no gassing
Ideal for use around sensitive
electronic equipment
Extended shelf life,
low self-discharge rate
Enhanced recharging efficiency
Resistance to vibration
Delivers the best combination starting,
cycling, and deep cycle service
Operation in cold temperatures
Superior deep cycle life and resiliency
to deep discharge damage
Gel or Gelled Electrolyte batteries
Batteries utilize special one-way, pressure-relief valves
and must never be opened.
Requires no electrolyte maintenance unlike deep cycle
flooded batteries that require frequent checking and
adjustment of electrolyte levels.
Uses a recombination reaction to prevent the escape of
hydrogen and oxygen gases normally lost in a flooded
lead-acid battery (particularly in deep cycle applications).
Spillproof design enables installation in virtually any
position (upside-down installation is not recommended).
Has a higher tolerance against damage from deep
discharge. These batteries have optimized amounts of
electrolyte (which is also referred to as “acid-starved”) so
that they use the power in the acid before they use the
power in the plates. This minimizes the destructive nature
of ultra-deep discharges. Ultra-deep discharging is what
causes plate shedding, which can destroy a battery.
(most sizes) (many sizes)
Cold engine cranking
Features and benefits that make our
VRLA batteries unique
East Penn Expertise
East Penn builds VRLA batteries to the highest standards.
Our manufacturing process features improved controls
using state-of-the-art computers and the latest manufacturing
technology and equipment. VRLA batteries produced by East
Penn consistently meet the highest quality performance and
life standards.
Major difference between Gel
and AGM battery performance
A Gel battery is better suited for super-deep discharge applications, which means it can withstand deeper discharges
without damaging the battery’s performance. However, due to
the physical properties of the gelled electrolyte, Gel battery
power declines faster than an AGM battery as the temperature
drops below 32ºF (0ºC). AGM batteries excel for high current,
high power applications and in extremely cold environments.
AGM batteries deliver a better dual purpose solution for a
combination of starting and accessory power.
One-Way, Pressure-Relief Valves
A critical feature of any VRLA battery is the quality of the sealing valve. Not only must the valve safely release excessive
pressure and gas, but it must also keep the cell from being
contaminated by the atmosphere. Oxygen contamination will
discharge and eventually ruin a VRLA battery. Our valves
are UL recognized and 100% tested. The benefit is reliable
performance and long life.
Exclusive Gel Formula & Computerized Mixing
of each element, similar to the wrap in an industrial battery.
The result is longer service life.
Proper gel mixing is critical to life and performance. Our
state-of-the-art gel battery manufacturing facility is one of
the finest in the world with a proprietary computerized gel
mixing operation. Our exclusive formula is mixed using
computer control in every stage of the process. Computer
control delivers superior consistency for gel battery
performance that is unequaled. Our temperaturecontrolled process and specially designed equipment
assures a homogenous gel. Our equipment was designed
by our engineers specifically for gel mixing – even down to
the contour of the tank bottoms and feed pipe locations.
AGM Ultra-Premium Glass Mat Separators
Variations in separator properties can be detrimental to the
AGM battery’s functional performance. East Penn uses
glass mats that are engineered to have consistency and an
ideal balance of critical properties. This attention to detail
results in high performance and long life.
n High absorption and retention rate holds acid securely in
glass fibers to prevent uneven saturation and acid stratification (see explanation of acid stratification under Acid
Stratification Prevention section).
n Thick, highly compressible mats provide padded protection around plates and absorb shock and vibration. This
maintains compression force over the entire surface of
the positive plate prohibiting shedding, which results in
capacity degradation. An AGM separator contains no
materials subject to failure from oxidation.
n Low electrical resistance from electrolyte holding fibers
and micro-porous composition optimizes current flow
between plates for a more efficient transfer of power.
n Durable mats are wrapped around the bottom of the
plate and are wider than the plates. This inhibits failures
from direct contact electrical plate shorts or shorts from
the build-up of material on the battery elements.
Exclusive AGM Electrolyte and Filling Process
Our AGM electrolyte contains high purity sulfuric acid and
pure, demineralized and deionized water. Avoiding impurities
enables the battery to function at the critical performance
levels necessary of the recombinant principle utilized in a
valve-regulated design. This assures minimized gassing as
well as water and capacity loss providing longer service life
and sustained performance.
The AGM filling process assures that each cell is saturated
with the maximum amount of electrolyte that can be held by
the separators, without leaving excess electrolyte that could
spill or leak.
Multi-Staged Filling and Vacuuming Operation
Exclusive Alloy Compositions
Our gel process fills and vacuums each cell several times. This
multi-step process assures complete evacuation of air and
complete gel-to-plate contact. Our computerized process also
weighs every SLI and Stationary battery before and after filling
as a check for proper gel levels. The result is a battery with
more consistent and reliable performance.
Our AGM topping process assures that the maximum retainable electrolyte quantity is held within the battery separators,
to produce a complete electrolyte-to-plate contact optimizing
battery performance and power.
Our exclusive alloy compositions provide the optimal combination of longer shelf life, more power conductance, enhanced
durability, and superior corrosion resistance. By using special
grain refiners, we can dramatically improve performance and
life. Calcium strengthens the grid for processing in the plant
so that its integrity is upheld in the battery to withstand the
forces of vibration and shock in service.
Heavy-Duty Grid Style Design
for Heavy-Duty Service
Gel Ultra-Premium, Glass Mat, Double
Insulating Separators
East Penn uses a high-performance deep cycle grid designed
for durability. The thick grid wires not only lock the active
material onto the grid, but also act as “bus bars” to collect and
direct the energy to the terminals.
Another critical component is the separator, which isolates
the positive from the negative plate. The separator must
allow maximum charge flow between the plates for maximum performance.
East Penn’s Gel battery utilizes a separator with two layers:
n The first fiberglass sheet layer maintains compression
force over the entire surface of the positive plate prohibiting active material shedding. The fiberglass strands
from this layer also prevent shedding by embedding
themselves into the surface of the plates. This acts like
reinforcing rods in concrete. These extra reinforcements
lock the active material to prevent capacity degradation
for longer life performance.
n The second layer is a porous organic polymer. The quantity and size of the pores is optimized to balance the
performance characteristics of the battery with its life
characteristics. This layer has ribs on both sides to allow
gel to reach the entire surface of both plates and to
maintain the correct plate spacing.
Acid Stratification Prevention
Acid stratification can occur in conventional flooded cells.
During charge, acid is released at the plate surfaces. During
discharge, acid is consumed at the plate surfaces. Since the
concentration is not uniform, diffusion (spontaneous mixing
by random molecular motions) begins. If this mixing
occurred rapidly, stratification would not occur, but it is
relatively slow, allowing lighter parts of electrolyte to “float”
toward the surface and heavier parts to “sink” toward the
bottom. The top portion of the plates do not perform as well
in contact with lower concentration electrolyte. The bottom
portion of the plates do not perform as well with the higher
concentration and will corrode prematurely. High voltage
“equalization” charging is sometimes used in flooded
batteries to make gas bubbles that remix the electrolyte.
Immobilized gel or separator-absorbed electrolyte will not “float”
or “sink” within itself when a non-uniform concentration exists
so it cannot stratify. Therefore, no high-voltage equalizing charge
is necessary. Simply recharge at the recommended recharge
settings. This means longer life and consistent performance.
Gel Polyester Element Wrap
To prevent life-shortening mossing in our gel batteries, we use
a special polyester fiber sheet that is wrapped around the edge
Proprietary Case, Cover, and One-Way,
Pressure-Relief Valve
humidity to create the optimal environment to facilitate the
curing process.
n Cast-On-Strap and Assembly Audits. Monitors lead
temperatures, line speed, alloy sampling, weld quality,
terminal burn depth, and leak testing all to ensure the
final assembled product meets rigid specifications and
standards providing a solid construction to support
premium VRLA battery products.
We design our own highly functional polypropylene cases,
valves, and covers. Many are molded in our on-site, state-of
the-art plastics molding facility. This provides ultimate control
of our high performance designs, quality and delivery to our
manufacturing plant, assuring you the highest quality battery
and most reliable service.
East Penn’s Quality Assurance Checks
Below are a few examples of the hundreds of quality checks
that are performed on Gel or AGM battery types to assure total
confidence in the performance and life of our batteries:
n Extended Shelf Stand Test. Before shipment, every battery
is required to stand for a period of time and ending voltages are analyzed. This extra quality assurance step verifies
that the batteries are optimized for electrical performance.
n Computer-Enhanced Filling Controls. During this computerized process, batteries are monitored and filled to
exacting levels for precision separator absorption and
complete permeation.
n Multi-Staged Filling and Vacuuming Process. Every battery is filled and vacuumed several times during this
computerized process. Multi-staged vacuuming assures
complete electrolyte-to-plate interface.
n Computerized Polarity Check. Every battery is checked by
computer analysis for proper polarity.
n Discharge Test. High-precision calibrated sensors allow
computers to monitor the voltage drop during this discharge to assure that every battery performs as designed.
n Grid Casting Inspections. Specified checks such as alloy
sampling, lead pot temperatures, ladle temperatures, grid
weight and thickness analysis assures patented alloy blend
and precise conditions for proper grid formation and application into battery production.
n Acid Mixing Checks. Regulatory acid temperature
and specific gravity monitoring optimizes battery
performance and longevity.
n Paste Mixing Monitoring. Computer-assisted formula
monitoring and extensive acid gravity and temperature
checks provide best attributes for paste adhesion, power
absorption and delivery performance.
n Paste-to-Grid Application Monitoring. Temperature,
thickness, weight and line speed analysis assures proper
adhesion and extended service life.
n Curing Checks. Assures proper time, temperature, and
What do I need to know about
VRLA battery charging?
All lead-acid batteries release hydrogen from the negative
plate and oxygen from the positive plate during charging.
VRLA batteries have one-way, pressure-relief valves.
Without the ability to retain pressure within the cells, hydrogen and oxygen would be lost to the atmosphere, eventually
drying out the electrolyte and separators.
Voltage is electrical pressure (energy per unit of charge).
Charge (ampere-hours) is a quantity of electricity. Current
(amperes) is electrical flow (charging speed). A battery can
only store a certain quantity of electricity. The closer it gets
to being fully charged, the slower it must be charged.
Temperature also affects charging. If the right voltage is used
for the temperature, a battery will accept charge at its ideal
rate. If too much voltage is used, charge will be forced
through the battery faster than it can be stored.
Reactions other than the charging reaction also occur to
transport this current through the battery—mainly gassing.
Hydrogen and oxygen may be given off faster than the
recombination reaction. This raises the pressure until the
one-way, pressure-relief valve opens. The gas lost cannot
be replaced. Any VRLA battery will dry out and fail prematurely if it experiences excessive overcharging.
Note: It is too much voltage that initiates this problem, not too
much charge — a battery can be “over-charged” (damaged
by too much voltage) even though it is not fully “charged.”
Never install any lead-acid battery in a sealed container
or enclosure. Hydrogen gas must be allowed to escape.
Can continual undercharging
harm a VRLA battery?
In many respects, undercharging is as harmful as overcharging. Keeping a battery in an undercharged condition
allows the positive grids to corrode and the plates to
shed, dramatically shortening life. Also, an undercharged
battery must work harder than a fully charged battery,
which contributes to short life as well.
An undercharged battery has a greatly reduced capacity. It
may easily be inadvertently over-discharged and eventually
Do VRLA batteries have a “memory”
like Ni-Cad batteries?
affected area with water immediately and consult a physician if splashed in the eyes. Consult MSDS for additional
precautions and first aid measures.
2. Prohibit smoking and open flames, and avoid arcing in
the immediate vicinity of the battery.
3. Do not wear metallic objects, such as jewelry, while
working on batteries. Do not store un-insulated tools in
pockets or tool belt while working in vicinity of battery.
4. Keep the top of the battery dry and clear of all tools and
other foreign objects.
5. Provide adequate ventilation as regulated by Federal,
State and Local codes and follow recommended
charging voltages.
6. Extinguishing media: Class ABC extinguisher. Note: CO2
may be used but not directly on the cells due to thermal
shock and potential cracking of cases.
7. Never remove or tamper with pressure-relief valves.
Warranty void if vent valve is removed.
One of the major disadvantages of nickel-cadmium (ni-cad)
batteries is that after shallow discharge cycles, the unused
portions of the electrodes “remember” the previous cycles
and are unable to sustain the required discharge voltage
beyond the depth of the previous cycles. The capacity is
lost and can only be restored by slowly discharging completely (generally outside the application), and properly
recharging. VRLA lead-acid batteries do not exhibit this
robbing effect known as memory.
What are the safety precautions
for VRLA batteries?
Although all valve-regulated batteries have the electrolyte
immobilized within the cell, the electrical hazard associated
with batteries still exists. Work performed on these batteries
should be done with the tools and the protective equipment
listed below. Valve-regulated battery installations should be
supervised by personnel familiar with batteries and battery
safety precautions.
Can VRLA batteries be installed
in sealed battery boxes?
Protective Equipment
To assure safe battery handling, installation and maintenance,
the following protection equipment should be used:
n Safety glasses or face shield (Consult application
specific requirements)
n Acid-resistant gloves
n Protective aprons and safety shoes
n Proper lifting devices
n Properly insulated tools
NO! Never install any type of battery in a completely sealed
container. Although most of the normal gasses (oxygen and
hydrogen) produced in a VRLA battery will be recombined and
not escape, oxygen and hydrogen will escape from the
battery in an overcharge condition (as is typical of any
type battery).
These potentially explosive gasses must be allowed to vent
to the atmosphere and must never be trapped in a sealed
battery box or tightly enclosed space!
Does depth of discharge affect cycle life?
Consult user manual of specific application for safety &
operating requirements. The following safety procedures
should be followed during installation: (Always wear safety
glasses or face shield.)
1. These batteries are sealed and contain no free flowing
electrolyte. Under normal operating conditions, they do
not present any acid danger. However, if the battery jar,
case, or cover is damaged, acid could be present.
Sulfuric acid is harmful to the skin and eyes. Flush
Yes! The harder any battery has to work, the sooner it will fail.
The shallower the average discharge, the longer the life.
It’s important to size a battery system to deliver at least twice
the energy required, to assure shallow discharges.
Follow these tips for the longest life:
Proposition 65
Batteries, battery posts, terminals and related accessories
contain lead and lead compounds, and other chemicals known
to the state of California to cause cancer and birth defects or
other reproductive harm. Wash hands after handling.
Avoid ultra-deep discharges. The definition of ultra-deep
discharge may vary with application and battery type.
n Don’t leave a battery at a low stage of charge for an
extended length of time. Charge a discharged battery as
soon as possible.
n Don’t cycle a battery at a low state of charge without
regularly recharging fully.
Use the highest initial charging current available (up to 30%
of the 20-hour capacity per hour) while staying within the
proper temperature-compensated voltage range.
has time to take place, each cell can hold an internal gas pressure above external pressure before venting. Batteries with very
large cells will slightly bulge as this normal pressure builds.
This is especially noticeable at higher temperatures because
the polypropylene case is more pliable when warm. Therefore,
a certain amount of bulge is normal. If a battery bulges severely on charge, this is not normal. It is an indication of a blocked
valve or an overcharge situation. Such a battery should be
removed from service.
What is a thermal runaway?
The appropriate charge voltage depends on the battery temperatures. A warmer battery requires a reduced voltage. If the
voltage is not reduced, current accepted by the battery
increases. When the current increases, the internal heating
increases. This can rise to destructive levels if not taken into
Thermal runaway can be prevented with:
n Temperature compensation monitoring at the battery —
not at the charger.
n Limiting charging currents to appropriate levels.
n Allowing for adequate air circulation around the batteries.
n Using timers or ampere-hour counters.
n Using smart chargers that recognize the signature of a
thermal runaway event which will shut the charger down.
ACTIVE MATERIAL — The porous structure of lead compounds
that produce and store electrical energy within a lead-acid battery.
The active material in the positive plates is lead dioxide and that in
the negative is metallic sponge lead. When an electrical circuit is
created, these materials react with sulfuric acid during charging
and discharging according to the following chemical reaction:
PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.
AGM (Absorbed Glass Mat) — A type of non-woven separator
material comprised almost entirely of glass microfibers that
absorbs and retains the electrolyte leaving no free electrolyte in
the cell to spill. VRLA batteries made with this material are often
referred to as “AGM” batteries.
AMPERE (Amp, A) — The unit of measure of the electron flow
rate, or current, through a circuit.
AMPERE-HOUR (Amp-Hr, Ah) — A unit of measure for a battery’s
electrical storage capacity, obtained by multiplying the current in
amperes by the time in hours of discharge. (Example: A battery
that delivers 5 amperes for 20 hours delivers 5 amperes X 20
hours = 100 Amp-Hr of capacity.)
Why do some VRLA batteries have a concave or
convex appearance?
The gas pressure in a VRLA battery can be lower than ambient pressure under certain circumstances. This partial
vacuum will pull the container walls and cover inward. This
may give the ends, sides of each cell, and tops of each cell a
noticeable concave (inwardly dished) appearance. This is
normal. The product is not defective. Its performance is not
compromised in any way. In some situations charging will
reduce or eliminate this appearance. Internal gas pressure
being lower than external pressure has several potential
causes that can operate alone or in combination. The
recombination process continues after charging ends
consuming most of the headspace oxygen — decreasing
internal pressure. An increase in external pressure will result
from a decrease in altitude. Cooling the battery reduces the
internal gas pressure by contraction and also by causing some
water vapor to return to liquid form. Severe discharging
shrinks the volume of the internal materials. This leaves more
volume for the gas to fill reducing the internal pressure.
To prevent the permanent loss of gases so that recombination
BOOST CHARGE — The process of ensuring that the cells and
plates within a battery are charged sufficiently for the battery to
perform its desired function. Boost charging is typically done for a
short duration at a high current.
CAPACITY — The capacity of a battery is specified as the number
of Amp-Hrs that the battery will deliver at a specific discharge rate
and temperature. The capacity of a battery is not a constant value
and is seen to decrease with increasing discharge rate. The capacity of a battery is affected by a number of factors such as: active
material weight, density of the active material, adhesion of the
active material to the grid, number, design and dimensions of
plates, plate spacing, design of separators, specific gravity and
quantity of available electrolyte, grid alloys, final limiting voltage,
discharge rate, temperature, internal and external resistance, age,
and life history of the battery.
CONTAINER AND COVER — The reservoir and lid containing the
battery parts and electrolyte made from impact and acid resistant
material such as polypropylene.
CELL — The basic electrochemical current-producing unit in a
battery, consisting of a set of positive plates, negative plates,
electrolyte, separators, and casing. In a lead-acid battery the cell
has an open-circuit voltage of approximately 2-volts. There are
six cells in a 12-volt lead-acid battery.
CIRCUIT — An electrical circuit is the path followed by a flow of
and plates within a battery are all at full charge and that the electrolyte is uniform and free of stratification. This is normally done
by charging the battery under controlled conditions (charge current, time and upper voltage limits are usually specified).
electrons. A closed circuit is a complete path. An open circuit has
a broken, or disconnected, path.
CIRCUIT (Series) — A circuit that has only one path for the flow
of current. Batteries arranged in series are connected with negative
of the first to positive of the second, negative of the second to
positive of the third, etc. If two 12-volt batteries of 50 amperehours capacity each are connected in series, the circuit voltage is
equal to the sum of the two battery voltages, or 24 volts, and the
ampere-hour capacity of the combination is 50 ampere-hours.
FORMATION — In battery manufacturing, formation is the process of charging the battery for the first time. Electrochemically,
formation changes the lead oxide paste on the positive grids into
lead dioxide and the lead oxide paste on the negative grids into
metallic sponge lead.
GEL — Electrolyte that has been immobilized by the addition of a
chemical agent, normally fine silica, to prevent spillage. Batteries
made with gelled electrolyte are often referred to as Gel batteries.
Gel batteries are one typical type of VRLA battery.
CIRCUIT (Parallel) — A circuit that provides more than one path
for the flow of current. A parallel arrangement of batteries (usually of like voltages and capacities) has all positive terminals
connected to a conductor and all negative terminals connected to
another conductor. If two 12-volt batteries of 50 ampere-hour
capacity each are connected in parallel, the circuit voltage is 12
volts, and the ampere-hour capacity of the combination is 100
GRID — A lead alloy framework that supports the active material
of a battery plate and conducts current.
GROUND — The reference potential of a circuit. In automotive
use, the result of attaching one battery cable to the body or frame
of a vehicle that is used as a path for completing a circuit in lieu of
a direct wire from a component. Today, over 99% of automotive
and LTV applications, use the negative terminal of the battery as
the ground.
COLD CRANK RATING — The cold crank rating refers to number
of amperes a lead-acid battery at 0°F (-17.8°C) can deliver for 30
seconds and while maintaining at least 7.2 volts (1.2 volts per
cell). This is commonly referred to as CCA (Cold Cranking Amps).
CONDUCTANCE — The ability to transmit current in a circuit or
HYDROMETER — A device used to measure the strength (i.e., the
concentration of sulfuric acid in the electrolyte) of the electrolyte
through specific gravity of the electrolyte.
CORROSION — The chemical or electrochemical reaction between
a material, usually a metal, and its environment that produces a
deterioration of the material and its properties. The positive lead
grids in a battery gradually corrode in service often leading to battery failure. Battery terminals are subject to corrosion if they are
not properly maintained.
INTERCELL CONNECTORS — Lead structures that connect
adjoining cells in series, positive of one cell to the negative of the
next, within a battery.
CURRENT — The rate of flow of electricity, or the movement of
electrons along a conductor. It is comparable to the flow of a
stream of water. The unit of measure for current is the ampere.
LOAD TESTER — An instrument that draws current (discharges)
from a battery using an electrical load while measuring voltage. It
determines the battery’s ability to perform under actual discharge
CURRENT (ALTERNATING) (AC) — A current that varies periodically in magnitude and direction. A battery does not deliver
alternating current (AC).
LOW WATER LOSS BATTERY — A battery that requires little to no
water additions under normal operating conditions; also referred
to as maintenance-accessible batteries.
CURRENT (DIRECT) (DC) — An electrical current flowing in an
electrical circuit in one direction only. A secondary battery delivers
direct current (DC) and must be recharged with direct current in
the opposite direction of the discharge.
MAINTENANCE-FREE — A battery that normally requires no
service watering during its lifetime of use.
NEGATIVE — Designating, or pertaining to, electrical potential.
The negative battery terminal is the point from which electrons
flow during discharge.
CYCLE — In a battery, one discharge plus one recharge equals
one cycle.
OHM — A unit for measuring electrical resistance or impedance
within an electrical circuit.
DISCHARGING — When a battery is delivering current, it is said to
be discharging.
OHM’S LAW — Expresses the relationship between volts (V) and
amperes (I) in an electrical circuit with resistance (R). It can be
expressed as follows:
V = IR
Volts (V) = Amperes (I) x Ohms (R). If any two of the three
values are known, the third value can be calculated using the
above equation.
ELECTROLYTE — In a lead-acid battery, the electrolyte is sulfuric
acid diluted with water. It is a conductor that supplies water and
sulfate for the electrochemical reaction:
PbO2 + Pb + 2H2SO4 = 2PbSO4 + 2H2O.
ELECTRONIC TESTER — An electronic device that assesses the
condition of a battery through an ohmic measurement such as
resistance or conductance, typically without drawing large current loads.
OPEN CIRCUIT VOLTAGE — The voltage of a battery when it is
not delivering or receiving power.
PLATES — Thin, flat structures comprised of a grid and active
material. The grid supports the active material and conducts electrons out of the cell. Plates are either positive or negative,
ELEMENT — A set of positive and negative plates assembled with
EQUALIZATION CHARGE — The process of ensuring that the cells
under the same discharge conditions. If the battery is fully
charged the “State of Charge” is said to be 100%.
depending on the active material they hold.
POSITIVE — Designating, or pertaining to, a kind of electrical
potential; opposite of negative. A point or terminal on a battery
having higher relative electrical potential. The positive battery terminal is the point to which electrons flow during discharge.
PRIMARY BATTERY — A battery that can store and deliver electrical energy but cannot be recharged. A lead-acid battery is NOT a
primary battery.
RESERVE CAPACITY RATING — The time in minutes that a new,
fully charged battery will deliver 25 amperes at 27°C (80°F) and
maintain a terminal voltage equal to, or higher than, 1.75 volts per
cell. This rating represents the time the battery will continue to
operate essential accessories if the alternator or generator of a
vehicle fails.
RESISTANCE — The opposition to the free flow of current in a
circuit or battery. It is commonly measured in Ohms.
SECONDARY BATTERY — A battery that can store and deliver
electrical energy and can be recharged by passing direct current
through it in a direction opposite to that of discharge. A lead-acid
battery is a secondary battery.
SEPARATOR — A porous divider between the positive and negative plates in a cell that allows the flow of ionic current to pass
through it, but not electronic current. Separators are made from
numerous materials such as: polyethylene, polyvinyl chloride,
rubber, glass fiber, cellulose, etc.
SHORT CIRCUIT — An unintended current-bypass in an electric
device or wiring. Outside the battery a short circuit is established when a conductive path is established between the two
terminals of a battery. Inside a battery, a cell short circuit is the
result of contact between the positive and negative plates and
will cause a cell to discharge and render the battery useless.
SPECIFIC GRAVITY (Sp. Gr. or SG) — Specific Gravity is a
measure of the electrolyte concentration in a battery. This measurement is based on the density of the electrolyte compared to
the density of water and is typically determined by the use of a
hydrometer (see Hydrometer). By definition, the specific gravity of
water is 1.00 and the specific gravity of the sulfuric acid electrolyte in a typical fully charged battery is 1.265-1.285. Specific
gravity measurements are typically used to determine if the battery is fully charged or if the battery has a bad cell.
STRATIFICATION — The unequal concentration of electrolyte due
to density gradients from the bottom to the top of a cell. This condition is encountered most often in batteries recharged from a
deep discharge at constant voltage without a great deal of gassing.
Continued deep cycling of a ‘stratified’ battery will result in softening of the bottoms of the positive plates. Equalization charging is a
way to avoid acid stratification.
SULFATION — The generation or conversion of the lead sulfate
discharge in the plates to a state that resists normal recharge.
Sulfation often develops when a battery is stored or cycled in a
partially discharged state at warm temperatures.
TERMINALS — The electrical structures on the battery to which
the external circuit is connected. Typically, batteries have either
top-terminals (posts) or side-terminals. Some batteries have both
types of terminals (dual-terminal).
VENTS — Mechanisms that allow gasses to escape from the battery while retaining the electrolyte within the case. Flame arresting
vents typically contain porous disks that reduce the probability of
an internal explosion as a result of an external spark. Vents come
in both permanently fixed and removable designs.
VOLT — The unit of measure for electrical potential or voltage.
VOLTMETER — An electronic device used to measure voltage,
normally in a digital format.
VOLTAGE DROP — The net difference in the electrical potential
(voltage) when measured across a resistance or impedance
(ohms). Its relationship to current is described in Ohm’s law.
VRLA — Valve Regulated Lead Acid battery. AGM and Gel are the
two types of VRLA batteries. These batteries have no “free” liquid
electrolyte and in the cell operate on the oxygen recombination
cycle, which is designed to minimize water loss. VRLA batteries
feature valves that have a one-way, pressure-relief design. These
low-pressure valves prohibit air entering the cell while permitting gases to vent from the cell if necessary. The pressure
maintained in the battery, though only very slight, is required to
facilitate the oxygen recombination reaction, which converts the
oxygen generated at the positive plates back into water.
STATE OF CHARGE — The amount of deliverable low-rate electrical energy stored in a battery at a given time expressed as a
percentage of the energy when fully charged and measured
East Penn Manufacturing Co. Lyon Station, PA 19536-0147
E.P.M. Form No. 1927
Phone: 610-682-6361
© 2015 by EPM Printed in U.S.A.
Fax: 610-682-4781
Order Department Hotline: 610-682-4231
All data subject to change without notice. No part of this document may be copied or
reproduced, electronically or mechanically, without written permission from the company.
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