ity. Refer to Battery Load Test. If the battery will
endure a load test, return the battery to use. If bat-
tery will not endure a load test, it must be replaced.
Properly clean and inspect battery hold downs, tray,
terminals, cables, posts, and top before completing
service. Also refer to Group 8B, Battery/Starter/Gen-
erator Service.
CHARGING TIME REQUIRED
The time required to charge a battery will vary de-
pending upon the following factors:
• SIZE OF BATTERY
A completely discharged large heavy-duty battery
requires more than twice the recharging time as a
completely discharged small capacity battery (Fig.
16).
• 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,
current accepted by battery will be very low at first.
In time, the battery will accept a higher rate as bat-
tery warms.
• CHARGER CAPACITY: A charger which, can sup-
ply only five amperes will require a much longer pe-
riod of charging than a charger that can supply 30
amperes or more.
• STATE OF CHARGE: A completely discharged
battery requires more charging time than a partially
charged battery. Electrolyte is nearly pure water in a
completely discharged battery. At first, the charging
current amperage will be low. As water is converted
to sulfuric acid inside the battery, the current amp
rate will rise. Also, the specific gravity of the electro-
lyte will rise, bringing the green dot (Fig. 5) into
view.
WARNING:
NEVER
EXCEED
20
AMPS
WHEN
CHARGING A COLD -1°C (30°F) BATTERY. PER-
SONAL INJURY MAY RESULT.
CHARGING COMPLETELY DISCHARGED
BATTERY
The following procedure should be used to recharge
a completely discharged battery. Unless procedure is
properly followed, a good battery may be needlessly
replaced (Fig. 17).
(1) Measure the voltage at battery posts with a
voltmeter accurate to 1/10 volt (Fig. 18). If below 10
volts, charge current will be low, and it could take
some time before it accepts a current in excess of a
few milliamperes. Such low current may not be de-
tectable on amp meters built into many chargers.
(2) Connect charger leads. Some chargers feature
polarity protection circuitry which, prevents opera-
tion unless charger is connected to battery posts cor-
rectly. A completely discharged battery may not have
enough voltage to activate this circuitry. This may
happen even if the leads are connected properly.
(3) Battery chargers vary in the amount of voltage
and current they provide. For the time required for
the battery to accept measurable charger current at
various voltages, refer to Fig. 17. If charge current is
still not measurable after charging period the battery
should be replaced. If charge current is measurable
during charging time, the battery may be good, and
charging should be completed in the normal manner.
Fig. 16 Battery Charging Time
Fig. 17 Charge Rate
Fig. 18 Voltmeter Accurate to 1/10 Volt (Connected)
8A - 8
BATTERY/STARTING/CHARGING SYSTEMS DIAGNOSTICS
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