Dodge RAM TRUCK 1500 1995 Service Manual page 336

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BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS 8A - 3
The battery is vented to release excess gas that is
created when the battery is being charged or dis­
charged. However, even with these vents, hydrogen
gas can collect in or around the battery. If hydrogen
gm is exposed to flame or sparks, it can ignite.
If the electrolyte level is low, the battery could arc in­
ternally and explode. If the battery is equipped with re­
movable cell caps, add distilled water whenever the
electrolyte level is below the top of the plates. If the bat­
tery cell caps cannot be removed, the battery must be
replaced when the electrolyte level is low.
WARNING: DO NOT ATTEMPT TO A S S I S T BOOST,
CHARGE, OR T E S T BATTERY W H E N E L E C T R O ­
LYTE L E V E L IS B E L O W THE TOP OF THE P L A T E S .
P E R S O N A L INJURY MAY OCCUR.
.BATTERY RATINGS
Currently, there are 2 commonly accepted methods for
rating and comparing battery performance. These rat­
ings are called Cold Cranking Amperage (CCA), and Re­
serve Capacity (RC). Be certain that a replacement
battery has CCA and RC ratings that equal or exceed
the original equipment specification for the vehicle be­
ing serviced. See Battery Classifications and Ratings
charts in Specifications at the back of this group.
COLD CRANKING AMPERAGE
The Cold Cranking Amperage (CCA) rating speci­
fies how much current (in amperes) the battery can
deliver for 30 seconds at -17.7°C (0°F). Terminal volt­
age must not fall below 7.2 volts during or after the
30 second discharge. The CCA required is generally
higher as engine displacement increases, depending
also upon the starter current draw requirements.
RESERVE CAPACITY
The Reserve Capacity (RC) rating specifies the
time (in minutes) it takes for battery terminal volt­
age to fall below 10.2 volts at a discharge rate of 25
amps. RC is determined with the battery fully-
charged at 26.7°C (80°F). This rating estimates how
long the battery might last after a charging system
failure, under minimum electrical load.
DIAGNOSIS
The battery must be completely charged and the
top, posts, and terminal clamps should be properly
cleaned before diagnostic procedures are performed.
Refer to Group 8B - Battery/Starter/Generator Ser­
vice for more information.
Models equipped with the diesel engine op­
tion are equipped with two 12-volt batteries
connected in parallel (positive-to-positive/nega­
tive-to-negative). The secondary battery on the
passenger side is dedicated to providing cur­
rent for the operation of the intake manifold
air heater. The primary battery on the driver's
side is dedicated to all other vehicle electrical
requirements. In order to ensure accurate diag­
nostic results, these batteries MUST be discon­
nected from each other as well as from the
vehicle electrical system when being tested.
The condition of a battery is determined by two cri­
teria:
(1) State-Of-Charge - This can be determined by
viewing the built-in test indicator, by checking spe­
cific gravity of the electrolyte (hydrometer test), or by
checking battery voltage (open circuit voltage test).
(2) Cranking Capacity - This can be determined by
performing a battery load test, which measures the abil­
ity of the battery to supply high-amperage current.
If the battery has a built-in test indicator, use this
test first. If it has no test indicator, but has remov­
able cell caps, perform the hydrometer test first. If
cell caps are not removable, or a hydrometer is not
available, perform the open circuit voltage test first.
The battery must be charged before proceeding
with a load test if:
• the built-in test indicator has a black or dark color
visible
• the temperature corrected specific gravity is less
than 1.235
• the open circuit voltage is less than 12.4 volts.
A battery that will not accept a charge is faulty
and further testing is not required. A battery that is
fully-charged, but does not pass the load test is
faulty and must be replaced.
Completely discharged batteries may take
several hours to accept a charge. See Charging
Completely Discharged Battery.
A battery is fully-charged when:
• all cells are gassing freely during charging
• a green color is visible in the sight glass of the
built-in test indicator
• three corrected specific gravity tests, taken at 1-hour
intervals, indicate no increase in specific gravity
• open circuit voltage is 12.4 volts or greater.
ABNORMAL BATTERY DISCHARGING
Any of the following conditions can result in abnor­
mal battery discharging:
(1) Corroded battery posts and terminals.
(2) Loose or worn generator drive belt.
(3) Electrical loads that exceed the output of the
charging system, possibly due to equipment installed
after manufacture or repeated short trip use.
(4) Slow driving speeds (heavy traffic conditions) or
prolonged idling with high-amperage draw systems in
use.
(5) Faulty circuit or component causing excessive
ignition-off draw. See Ignition-Off Draw in this group
for diagnosis.
(6) Faulty charging system.
(7) Faulty or incorrect battery.