Battery Testing; Hydrometer Test - Jeep 1979 CJ-5 Technical & Service Manual

BATTERIES 1D-5
(1) Remove vent caps from booster battery and
cover cap openings with dampened cloth.
CAUTION: If the vehicle is being jump-started by a
battery in another vehicle, the vehicles must not contact
each other.
(2) Connect jumper cable between positive posts of-
batteries. Positive post has " + " stamped on it. POS is
also embossed on battery cover in 1/8-inch letters adja-
cent to battery terminal.
(3) Connect one end of second jumper cable to nega-
tive terminal of booster battery. NEG is embossed on
battery cover in 1/8-inch letters adjacent to battery
terminal. Make certain clamps are making good contact.
DO NOT CONNECT OTHER END OF JUMPER
C A B L E TO N E G A T I V E T E R M I N A L OF D I S -
CHARGED BATTERY. Connect to screw, bracket or
nut on engine. Do not connect jumper to carburetor, air
cleaner or fuel line. Keep cable clear of belts and pulleys.
(4) When engine starts, remove jumper cables. Dis-
connect clamp on engine first.
(5) Discard cloth used to cover cap openings because
it has been exposed to sulfuric acid.
(6) Install battery caps.
T E S T l I t
General
NOTE: A complete battery test includes cleaning the
top of the battery case, cleaning terminals and cable
clamps and performing hydrometer and heavy load
tests.
The condition of a battery may be determined from
the results of two tests—state of charge (hydrometer
test) and ability to deliver current (heavy load test).
Refer to Battery Diagnosis and Repair Simplification
(DARS) Chart.
Perform the hydrometer test first. If specific gravity
indicates less than 1.225, the battery must be charged
before further testing can be done. A battery which does
not accept a charge is defective and no further testing is
required.
NOTE: A sulfated battery may require an overnight
slow charge to determine if the sulfation is light enough
to be broken down by a charge.
In rare cases where a battery goes dead and no appar-
ent cause can be found, the battery should be fully
charged and allowed to stand on a shelf for three to
seven days to determine if self-discharge is excessive.
The Self-Discharge Rate chart shows allowable self-dis-
charge 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 readings, taken at hourly intervals, indicate no
increase in specific gravity.
Hydrometer Test
NOTE: Periodically disassemble the hydrometer and
wash 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 (broken container, cover, loose post, etc.) that
would make the battery unserviceable. To read the hy-
drometer correctly, position the top surface of the elec-
trolyte in the hydrometer at eye level (fig. 1D-3).
Disregard the curvature of the liquid where the surface
rises against the float due to surface cohesion. Draw in
only enough electrolyte to keep the float off the bottom
of the hydrometer barrel with the bulb released. Keep
the hydrometer in a vertical position while drawing in
liquid and taking the reading. Be careful when inserting
the tip of the hydrometer into the cell to avoid damage
to separators. Broken separators could result in pre-
mature battery failure. !
B U L B -
B A R R E L -
F L O A T —
T H E R M O M E T E R .
/
D I S R E G A R D
SLIGHT
C U R V A T U R E
A battery which is over 75 percent charged and does
not pass the heavy load test is defective.
4 2 1 4 3
Fig. 1D-3 Hydrometer and Proper Method of Reading