required for low-maintenance batteries that is not
required on maintenance-free (sealed) batteries.
NOTE: Vehicles using a Maintenance-Free battery,
should be replaced with a Maintenance-Free battery.
Maintenance-free batteries have non-removable
battery vent caps (Fig. 1). Water cannot be added to
this battery. Under normal service the composition of
this battery reduces gassing and water loss at nor-
mal charge rates. If the battery electrolyte level
becomes low, this battery must be replaced.
Low-maintenance batteries have removable battery
cell caps (Fig. 2). Water can be added to this battery.
Under normal service the composition of this battery
reduces gassing and water loss at normal charge
rates.
The battery is a device used to store electrical
energy potential in a chemical form. When an electri-
cal load is applied to the battery terminals, an elec-
trochemical reaction occurs within the battery. This
reaction causes the battery to discharge electrical
current.
The battery is made up of six individual cells that
are connected in series. Each cell contains positive
charged plate groups made of lead oxide, and nega-
tively charged plate groups made of sponge lead. The
dissimilar metal plates are submerged in a sulfuric
acid and water solution called an electrolyte.
OPERATION
The battery has three major electrical system func-
tions: First, it provides an energy source for cranking
the engine; second, it acts as an electrical system
voltage stabilizer; third, it delivers electrical current
to operate various electrical systems in the vehicle,
for a limited time, when the electrical load exceeds
the generator output or during engine off conditions.
As the battery discharges, a gradual chemical
change takes place within each cell. The sulfuric acid
in the electrolyte combines with the plate material
causing both plates to slowly change to lead sulfate.
At the same time, oxygen from the positive plate
material combines with hydrogen from the sulfuric
acid, causing the electrolyte to become mainly water.
The chemical changes within the battery are
caused by the movement of excess or free electrons
between the positive and negative plate groups. This
movement of electrons produces a flow of electrical
current through the load device attached to the bat-
tery terminals. As the plate materials become more
similar chemically, and the electrolyte becomes less
acid, the voltage potential of each cell is reduced.
However, by charging the battery with a voltage
higher than that of the battery, the battery discharg-
ing process is reversed.
Charging the battery gradually changes the sul-
fated lead plates back into sponge lead and lead
oxide, and the water back into sulfuric acid. This
action restores the difference in the electron charges
deposited on the plates, and the voltage potential of
the battery cells.
For a battery to remain useful, it must be able to
produce high-amperage current over an extend
period. A battery must also be able to accept a charge
so that its voltage potential may be restored.
In addition to producing and storing electrical
energy, the battery serves as a capacitor, or voltage
stabilizer, for a vehicle’s electrical system. It absorbs
most abnormal or transient voltages caused by the
switching of any of the vehicle’s electrical compo-
nents.
The battery is vented to release excess hydrogen
gas that is created when the battery is being charged
or discharged. However, even with these vents, the
hydrogen gas can collect in or around the battery.
hydrogen gas is exposed to flame or sparks, it might
ignite.
If the electrolyte level is low, the battery may arc
internally and explode. If the battery is equipped
with removable cell caps, add distilled water when-
ever the electrolyte level is below the top of the
plates. If the battery cell caps cannot be removed, the
battery must be replaced if the electrolyte level
becomes low.
BATTERY CHARGER CAPACITY
DESCRIPTION
A charger which can supply only five amperes will
require a much longer period of charging than a
charger that can supply 20 amperes or more.
OPERATION
Refer to the individual battery charger instructions
for charging information.
BATTERY IGNITION OFF DRAW (IOD)
DESCRIPTION
The IOD fuse (M1) is located in the Junction Block.
Refer to the raised fuse or the cover of the Junction
Block for proper fuse location.
OPERATION
A completely normal vehicle will have a small
amount of current drain on the battery with the key
out of the ignition. It can range from 5 to 25 milli-
amperes after all the modules time out. If a vehicle
will not be operated for approximately a 20 days, the
IOD fuse should be pulled to eliminate the vehicle
electrical drain on the battery during storage.
8A - 2 BATTERY LH
DESCRIPTION AND OPERATION (Continued)
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