Dodge ram truck 3500 1996 Service Manual page 359

BR
BATTERY 8A -11
SERVICE PROCEDURES
( C o n t i n u e d )
is too low for the polarity-sensing circuitry to detect,
the charger will not operate. This makes It appear
that the battery will not accept charging current.
Refer to the Instructions provided with the battery
charger to bypass the polarity-sensing circuitry.
After the battery has been charged to 12.4 volts or
greater, perform a load test to determine the battery
cranking capacity. I f the battery will endure a load
test, return the battery to use. I f the battery will not
endure a load test,' i t Is faulty and must be replaced.
Clean and inspect the battery holddowns, tray, ter­
minals, posts, and top before completing service. See
the Battery Removal and installation procedures In
this group for more information.
CHARGING
A COMPLETELY DISCHARGED
BATTERY
The following procedure should be used to recharge
a completely discharged battery. Unless this proce­
dure is properly followed, a good battery may be
needlessly replaced.
(1) Measure the voltage at the battery posts with a
voltmeter, accurate to 1/10 (0.10) volt (Fig. 9). I f the
reading is below 10 volts, the charge current will be
low. I t could take some time before the battery
accepts a current greater than a few milliamperes.
Such low current may not be detectable on the
ammeters built into many chargers.
898A-12
Fig. 9 Voltmeter Accurate to 1/10 Volt Connected
(2) Disconnect and isolate the battery negative
cable. Connect the battery charger leads. Some bat­
tery chargers are equipped with polarity-sensing cir­
cuitry. This circuitry protects the charger and/or
battery from being damaged i f they are improperly
connected. I f the battery state-of-charge is too low for
the polarity-sensing circuitry to detect, the charger
will not operate. This makes it appear that the bat­
tery will not accept charging current. Refer to the
instructions provided with the battery charger to
bypass the polarity-sensing circuitry.
. (3) Battery chargers vary in the amount of voltage
and current they provide. The amount of time
required for a battery to accept measurable charger
current at various voltages is shown i n the Charge
Rate chart. I f the charge current is still not measur­
able at end of the charging time, the battery is faulty
and must be replaced. I f the charge current is mea­
surable during the charging time, the battery may be
good and the charging should be completed in the
normal manner.
Charge Rate
Voltage
Hours
16.0 volts maximum up to 4 hours
14.0 to 15.9 volts up to 8 hours
13.9 volts or less
up to 16 hours
CHARGING TIME REQUIRED
The time required to charge a battery will vary,
depending upon the following factors:
• Battery Capacity - A completely discharged
heavy-duty battery requires twice the charging time
of a small capacity battery.
• Temperature - A longer time will be needed to
charge a battery at -18°C (0°F) than at 27°C (80°F).
When a fast charger is connected to a cold battery,
the current accepted by the battery will be very low
at first. As the battery warms, i t will accept a higher
charging current rate (amperage).
• Charger Capacity - A charger that supplies
only 5 amperes will require a longer charging time. A
charger that supplies 20 amperes or more will
require a shorter charging time.
• State-Of-Charge - A completely discharged bat­
tery requires more charging time than a partially
discharged battery. Electrolyte is nearly pure water
in a completely discharged battery. At first, the
charging current (amperage) will be low. As the bat­
tery charges, the specific gravity of the electrolyte
will gradually rise..
Battery Charging Timetable
Charging
Amperage
5
Amperes
10
Amperes
20
Ampere
Open Circuit
Voltage
Hours Charging at 21 °C (70°F)
12.25 to 12.39 6 hours
3 hours
' 1.5 hours
12.00 to 12.24 8 hours 4 hours 2 hours
11.95
to
11.99
12 hours 6 hours 3 hours
10.00
to
11.94
14 hours 7 hours 3.5 hours
less than 10.00 See Charging Completely
Discharged Battery