Guide to VRLA Batteries

7
e
lectrons. 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 ampere-
hours capacity each are connected in series, the circuit voltage is
equal to the sum of the two battery voltages, or 24 volts, and the
a
mpere-hour capacity of the combination is 50 ampere-hours.
CIRCUIT (Parallel) — A circuit that provides more than one path
for the flow of current. A parallel arrangement of batteries (usu-
ally 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
ampere-hours.
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
battery.
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 bat-
tery failure. Battery terminals are subject to corrosion if they are
not properly maintained.
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.
CURRENT (ALTERNATING) (AC) — A current that varies periodi-
cally in magnitude and direction. A battery does not deliver
alternating current (AC).
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.
CYCLE — In a battery, one discharge plus one recharge equals
one cycle.
DISCHARGING — When a battery is delivering current, it is said to
be discharging.
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:
PbO
2
+ Pb + 2H
2
SO
4
= 2PbSO
4
+ 2H
2
O.
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 cur-
rent loads.
ELEMENT — A set of positive and negative plates assembled with
separators.
EQUALIZATION CHARGE — The process of ensuring that the cells
a
nd plates within a battery are all at full charge and that the elec-
trolyte is uniform and free of stratification. This is normally done
by charging the battery under controlled conditions (charge cur-
rent, time and upper voltage limits are usually specified).
FORMATION — In battery manufacturing, formation is the pro-
cess 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
m
etallic 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.
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.
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.
INTERCELL CONNECTORS — Lead structures that connect
adjoining cells in series, positive of one cell to the negative of the
next, within a battery.
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
conditions.
LOW WATER LOSS BATTERY — A battery that requires little to no
water additions under normal operating conditions; also referred
to as maintenance-accessible batteries.
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.
OHM — A unit for measuring electrical resistance or impedance
within an electrical circuit.
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.
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 elec-
trons out of the cell. Plates are either positive or negative,