Self-Discharging Rate; Hydrometer Test - Jeep 1987 Wrangler Workshop Manual

ELECTRICAL
BATTERIES
The condition of a battery may be determined
from the result of two tests - state of charge
(Hydrometer Test) and the ability to supply
current (Heavy Load Test).
Perform the hydrometer test first. If the specific
gravity is less than 1.225, the battery must be
charged before proceeding with further testing.
A battery that will not accept a charge is
defective and further testing is not necessary.
N O T E : A battery with sulfated plates may
require an overnight "slow charge" to determine
if the sulfate coating is thin enough to be
eliminated by a "charge".
A battery that has been fully charged but does
not pass the heavy load test is defective.
If a battery discharges and no apparent cause
can be determined, the battery should be fully
charged and allowed to stand on a shelf for three
to seven days to determine if the self-discharge
is excessive.
NOTE: The Self-Discharge Rate Chart lists the
amount of allowable self-discharge for the first
ten days of standing after a battery has been
fully charged.
A battery is fully charged when all cells are
gassing freely and three corrected specific
gravity tests, taken at one-hour intervals,
indicate no increase in specific gravity.
Apply a thin coating of petroleum jelly or silicone
grease to the cable terminals and the battery
posts.
Inspect the negative cable connections on the
engine and vehicle body for condition, security,
and electrical continuity.
Self-Discharging Rate
Temperature
Approximate Allowable
Self -OiKharfe Per Day
For First Ten Days
1 0 0 ° F ( 3 7 . 8 ° C )
8 0 ° F (26.7°C)
5 0 ° F (10°C)
0.0024 Specific Gravity
0.0009 Specific Gravity
0.0003 Specific Gravity
60338
Hydrometer
Test
N O T E : Periodically disassemble the hydro-
meter and wash the components with soap and
water. Inspect the float for possible leaks. If the
paper inside has turned brown, the float is
defective.
Prior to testing, visually inspect the battery for
any damage (cracked case or cover, loose post,
etc.) that would c a u s e the battery to be
unserviceable. To interpret the hydrometer
correctly, hold it with the top surface of the
electrolyte in the hydrometer at eye level.
Disregard the curvature of the liquid (1) where
the surface rises against the float because of
surface c o h e s i o n . R e m o v e only enough
electrolyte from the battery to keep the float (2)
off the bottom of the hydrometer barrel (3) when
pressure on the bulb (4) is released.
C-8