Open-Circuit Voltage Test; Testing Open-Circuit Voltage - Typical - Jeep 200 Cherokee Service Manual

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DIAGNOSIS AND TESTING (Continued)
rection factor is approximately a specific gravity
value of 0.004, which may also be identified as four
points of specific gravity. For each 5.5° C above 26.7°
C (10° F above 80° F), add four points. For each 5.5°
C below 26.7° C (10° F below 80° F), subtract four
points. Always correct the specific gravity for temper-
ature variation.
EXAMPLE: A battery is tested at -12.2° C (10° F)
and has a specific gravity of 1.240. Determine the
actual specific gravity as follows:
(1) Determine the number of degrees above or
below 26.7° C (80° F): 26.6° C - -12.2° C = 38.8° C
(80° F - 10° F = 70° F)
(2) Divide the result from Step 1 by 5.5° C (10° F):
38.8° C 5.5° C = 7 (70° F
(3) Multiply the result from Step 2 by the temper-
ature correction factor (0.004): 7 X 0.004 = 0.028
(4) The temperature at testing was below 26.7° C
(80° F); therefore, the temperature correction factor
is subtracted: 1.240 - 0.028 = 1.212
(5) The corrected specific gravity of the battery cell
in this example is 1.212.
Test the specific gravity of the electrolyte in each
battery cell. If the specific gravity of all cells is above
1.235, but the variation between cells is more than
fifty points (0.050), the battery should be replaced. If
the specific gravity of one or more cells is less than
1.235, charge the battery at a rate of approximately
five amperes. Continue charging the battery until
three consecutive specific gravity tests, taken at one-
hour intervals, are constant. If the cell specific grav-
ity variation is more than fifty points (0.050) at the
end of the charge period, replace the battery.
When the specific gravity of all cells is above 1.235,
and the cell variation is less than fifty points (0.050),
the battery may be load tested to determine its
cranking capacity. Refer to Load Test in this section
for the proper battery load testing procedures.

OPEN-CIRCUIT VOLTAGE TEST

A battery open-circuit voltage (no load) test will
show the state-of-charge of a battery. This test can be
used in place of the hydrometer test when a hydrom-
eter is not available, or for maintenance-free batter-
ies with non-removable cell caps.
WARNING:
• IF THE BATTERY SHOWS SIGNS OF FREEZ-
ING, LEAKING, LOOSE POSTS, OR LOW ELECTRO-
LYTE LEVEL, DO NOT TEST, ASSIST-BOOST, OR
CHARGE. THE BATTERY MAY ARC INTERNALLY
AND EXPLODE. PERSONAL INJURY AND/OR VEHI-
CLE DAMAGE MAY RESULT.
• EXPLOSIVE HYDROGEN GAS FORMS IN AND
AROUND THE BATTERY. DO NOT SMOKE, USE
FLAME, OR CREATE SPARKS NEAR THE BATTERY.
10° F = 7)
PERSONAL INJURY AND/OR VEHICLE DAMAGE
MAY RESULT.
• THE BATTERY CONTAINS SULFURIC ACID,
WHICH IS POISONOUS AND CAUSTIC. AVOID CON-
TACT WITH THE SKIN, EYES, OR CLOTHING. IN
THE EVENT OF CONTACT, FLUSH WITH WATER
AND CALL A PHYSICIAN IMMEDIATELY. KEEP OUT
OF THE REACH OF CHILDREN.
• IF THE BATTERY IS EQUIPPED WITH REMOV-
ABLE CELL CAPS, BE CERTAIN THAT EACH OF
THE CELL CAPS IS IN PLACE AND TIGHT BEFORE
THE BATTERY IS RETURNED TO SERVICE. PER-
SONAL INJURY AND/OR VEHICLE DAMAGE MAY
RESULT FROM LOOSE OR MISSING CELL CAPS.
Before proceeding with this test, completely charge
the battery. Refer to Battery Charging in the index
of this service manual for the location of the proper
battery charging procedures.
(1) Before measuring the open-circuit voltage, the
surface charge must be removed from the battery.
Turn on the headlamps for fifteen seconds, then
allow up to five minutes for the battery voltage to
stabilize.
(2) Disconnect and isolate both battery cables, neg-
ative cable first.
(3) Using a voltmeter connected to the battery
posts (see the instructions provided by the manufac-
turer of the voltmeter), measure the open-circuit volt-
age (Fig. 9).
Fig. 9 Testing Open-Circuit Voltage - Typical
See the Open-Circuit Voltage chart. This voltage
reading will indicate the battery state-of-charge, but
will not reveal its cranking capacity. If a battery has
an open-circuit voltage reading of 12.4 volts or
greater, it may be load tested to reveal its cranking
capacity. Refer to Load Test in this section for the
proper battery load testing procedures.
BATTERY 8A - 11