Dodge RAM TRUCK 1500 1995 Service Manual page 338

BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 5
BUILT-IN TEST INDICATOR
A test indicator (hydrometer) built into the top of
the battery case, provides visual information for bat­
tery testing (Fig. 3). It is important when using the
test indicator that the battery be level and have a
clean sight glass to see correct indications. Additional
light may be required to view indicator.
WARNING: DO NOT U S E OPEN FLASHE A S A
S O U R C E O F ADDITIONAL LIGHT FOR VIEWING
T E S T INDICATOR. E X P L O S I V E HYDROGEN G A S
MAY B E P R E S E N T IN THE A R E A SURROUNDING
BATTERY.
Fig. 3 Built-in Test Indicator
Like a hydrometer, the built-in test indicator mea­
sures the specific gravity of the electrolyte. Specific
gravity will indicate battery state-of-charge. How­
ever, the test indicator will not indicate cranking ca­
pacity of the battery. See Load Test in this group for
more information.
Look into the sight glass and note the color of the
indicator (Fig. 4). See the following description, as
the color indicates:
• GREEN - indicates 75% to 100% state-of-charge.
The battery is adequately charged for further test­
ing or return to use. If the vehicle will not crank for
a minimum of 15 seconds with a fully-charged bat­
tery, perform Load Test.
• BLACK OR DARK - indicates 0% to 75% state-of-
charge.
The battery is inadequately charged and must be
charged until green indicator (Fig. 4) is visible in
sight glass (12.4 volts or more) before the battery is
tested further or returned to use. See Abnormal Bat­
tery Discharging in this group to diagnose cause of
discharged condition.
• YELLOW OR BRIGHT - indicates low electrolyte
level.
The electrolyte level in the battery is below test in­
dicator. A maintenance-free battery with non-remov­
able cell caps must be replaced if electrolyte level is
low. Water can be added to a low-maintenance bat­
tery with removable cell caps. A low electrolyte level
may be caused by an over-charging condition. See
Charging System in this group to diagnose an over­
charging condition.
WARNING: DO NOT ATTEMPT TO CHARGE, TEST,
OR A S S I S T BOOST BATTERY W H E N Y E L L O W OR
BRIGHT COLOR I S V I S I B L E IN SIGHT G L A S S OF
T E S T INDICATOR. LOW ELECTROLYTE L E V E L CAN
A L L O W BATTERY TO ARC INTERNALLY AND EX­
PLODE. P E R S O N A L INJURY MAY OCCUR.
TEST INDIGATOR/STATE-OF-CHARGE
100% 75% O
LOW
100% 75% O
ELECTROLYTE
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GREEN
BLACK YELLOW
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Fig. 4 Built-in Test Indicator Sight Glass
HYDROMETER TEST
The hydrometer test reveals the battery state-of-
charge by measuring the specific gravity of the elec­
trolyte. This test cannot be performed on batteries
with non-removable cell caps. If battery has non-re­
movable cell caps, see Built-in Test Indicator or Open
Circuit Voltage Test.
Specific gravity is a comparison of the density of
the electrolyte to the density of pure water. Pure wa­
ter has a specific gravity of 1.000, and sulfuric acid
has a specific gravity of 1.835. Sulfuric acid makes
up approximately 35% of the electrolyte by weight, or
24% by volume.
In a fully-charged battery the electrolyte will have
a temperature corrected specific gravity of 1.260 to
1.290. However, a specific gravity of 1.235 or above is
satisfactory for battery load testing and/or return to
service.
Before testing, visually inspect battery for any
damage (cracked case or cover, loose posts, etc.) that
would cause the battery to be faulty. Then remove
cell caps and check electrolyte level. Add distilled wa­
ter if electrolyte level is below the top of the battery
plates.
To use the hydrometer correctly, hold it with the
top surface of the electrolyte at eye level. Refer to the
hydrometer manufacturer's instructions for correct
use of hydrometer. Remove only enough electrolyte
from the battery so the float is off the bottom of the
hydrometer barrel with pressure on the bulb re­
leased.