Jeep Cherokee XJ 1999 Manual - page 8
In a fully-charged battery the electrolyte will have
a temperature-corrected specific gravity of 1.260 to
1.290. However, a specific gravity of 1.235 or above is
satisfactory for battery load testing and/or return to
service.
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.
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 testing, visually inspect the battery for any
damage (a cracked case or cover, loose posts, etc.)
that would cause the battery to be faulty. Then
remove the cell caps and check the electrolyte level.
Add distilled water if the electrolyte level is below
the top of the battery plates.
See the instructions provided by the manufacturer
of the hydrometer for recommendations on the cor-
rect use of the hydrometer that you are using.
Remove only enough electrolyte from the battery cell
so that the float is off the bottom of the hydrometer
barrel with pressure on the bulb released.
CAUTION: Exercise care when inserting the tip of
the hydrometer into a cell to avoid damaging the
plate separators. Damaged plate separators can
cause early battery failure.
To read the hydrometer correctly, hold it with the
top surface of the electrolyte at eye level (Fig. 4).
Hydrometer floats are generally calibrated to indi-
cate the specific gravity correctly only at 26.7° C (80°
F). When testing the specific gravity at any other
temperature, a correction factor is required.
The correction 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 grav-
ity for temperature variation. Test the specific grav-
ity of the electrolyte in each battery cell.
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 (10):38.8°
C
4
5.5 = 7 (70° F
4
10 = 7)
(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
The corrected specific gravity of the battery cell in
this example is 1.212.
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 consecu-
tive specific gravity tests, taken at one-hour inter-
vals,
are
constant.
If
the
cell
specific
gravity
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),
Fig. 4 Hydrometer - Typical
8A - 8
BATTERY
XJ
DIAGNOSIS AND TESTING (Continued)