BATTERY TEST PROCEDURES ON-VEHICLE
INDEX
page
page
Battery Charging
. . . . . . . . . . . . . . . . . . . . . . . . . . 7
Battery Load Test
. . . . . . . . . . . . . . . . . . . . . . . . . 6
Battery Open Circuit Voltage Test
. . . . . . . . . . . . . 4
Causes of Battery Discharging
. . . . . . . . . . . . . . . 4
General Information
. . . . . . . . . . . . . . . . . . . . . . . . 3
State of Charge Tests
. . . . . . . . . . . . . . . . . . . . . . 4
Test Indicator
. . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
GENERAL INFORMATION
The battery stores, stabilizes, and produces electri-
cal current to operate various electrical systems in
the vehicle. The determination of whether a battery
is good or bad is made by the battery’s ability to ac-
cept a charge. It also must produce high amperage
current output over an extended period to be able to
start the vehicle. The capability of the battery to
store electrical current comes from a chemical reac-
tion. This reaction takes place between the sulfuric
acid solution electrolyte and the lead +/- plates in
each cell of the battery. As the battery discharges,
the plates react with the acid from the electrolyte.
When the charging system charges the battery, the
water is converted to sulfuric acid in the battery. The
amount of acid, specific gravity in the electrolyte can
be measured with a hydrometer. The factory in-
stalled battery is equipped with a built in hydrome-
ter as a test indicator (Figs. 3, 4 and 5) to help in
determining the battery’s state of charge. The factory
installed battery also is sealed. Water cannot and
should not be added.
The battery is vented to release gases that is cre-
ated when the battery is being charged and dis-
charged. The battery top, posts, and terminals should
be cleaned when other under hood maintenance is
performed (Fig. 3).
WARNING: DO NOT ASSIST BOOST, CHARGE, ADD
WATER, OR LOAD TEST BATTERY WHEN ELEC-
TROLYTE LEVEL IS BELOW THE TOP OF THE
PLATES. PERSONAL INJURY MAY OCCUR.
When the electrolyte level is below the top of the
plates a yellow or bright color indicator in sight glass
(Figs. 4 and 5), the battery must be replaced. Refer
to Test Indicator. The battery must be completely
charged with a green color in sight glass. The top,
posts, and terminals should be properly cleaned be-
fore diagnostic procedures are performed. Also refer
to Group 8B, Battery/Starter/Generator Service.
TEST INDICATOR
The test indicator a hydrometer is viewed through
a sight glass, it is built into the top of battery case
(Figs. 3, 4 and 5). This provides visual information
for battery testing. The test indicator sight glass is to
be used with diagnostic procedures described in this
Group.
Fig. 3 Battery Construction and Test Indicator
Fig. 4 Built in Test Indicator
Fig. 5 Test Indicator Sight Glass
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BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
8A - 3