Content .. 362 363 364 365 ..

Jeep Grand Cherokee WK. Manual - part 364

SPECIAL TOOLS

BATTERY SYSTEM SPECIAL TOOLS

8F - 8

BATTERY SYSTEM - SERVICE INFORMATION

BATTERY

DESCRIPTION

This vehicle is equipped with a single, 12-volt, mainte-
nance-free battery located in the engine compartment.
The battery is comprised of the following components:

•

Positive Post (1)

•

Vent (2)

•

Cell Cap (3)

•

Vent (4)

•

Cell Cap (5)

•

Vent (6)

•

Negative Post (7)

•

Indicator Eye (8) if equipped

•

Electrolyte Level (9)

•

Plate Groups (10)

•

Maintenance Free Battery assembly (11)

This battery is designed to provide a safe, efficient and reliable means of storing electrical energy in a chemical
form. This means of energy storage allows the battery to produce the electrical energy required to operate the
engine starting system, as well as to operate many of the other vehicle accessory systems for limited durations
while the engine and/or the charging system are not operating. The battery is made up of six individual cells that are
connected in series. Each cell contains positively charged plate groups that are connected with lead straps to the
positive terminal post, and negatively charged plate groups that are connected with lead straps to the negative ter-
minal post. Each plate consists of a stiff mesh framework or grid coated with lead dioxide (positive plate) or sponge
lead (negative plate). Insulators or plate separators made of a non-conductive material are inserted between the
positive and negative plates to prevent them from contacting or shorting against one another. These dissimilar metal
plates are submerged in a sulfuric acid and water solution called an electrolyte.

The battery Group Size number, the Cold Cranking Amperage (CCA) rating, and the Reserve Capacity (RC) rating
or Ampere-Hours (AH) rating can be found on the original equipment battery label. Be certain that a replacement
battery has the correct Group Size number, as well as CCA, and RC or AH ratings that equal or exceed the original
equipment specification for the vehicle being serviced. (Refer to 8 - ELECTRICAL/BATTERY SYSTEM - SPECIFI-
CATIONS) for the proper factory-installed battery specifications.

OPERATION

The battery is designed to store electrical energy in a chemical form. When an electrical load is applied to the
terminals of the battery, an electrochemical reaction occurs. This reaction causes the battery to discharge electrical
current from its terminals. As the battery discharges, a gradual chemical change takes place within each cell. The
sulfuric acid in the electrolyte combines with the plate materials, causing both plates to slowly change to lead sul-
fate. At the same time, oxygen from the positive plate material combines with hydrogen from the sulfuric acid, caus-
ing the electrolyte to become mainly water. The chemical changes within the battery are caused by the movement
of excess or free electrons between the positive and negative plate groups. This movement of electrons produces
a flow of electrical current through the load device attached to the battery terminals.

As the plate materials become more similar chemically, and the electrolyte becomes less acid, the voltage potential
of each cell is reduced. However, by charging the battery with a voltage higher than that of the battery itself, the
battery discharging process is reversed. Charging the battery gradually changes the sulfated lead plates back into
sponge lead and lead dioxide, and the water back into sulfuric acid. This action restores the difference in the elec-
tron charges deposited on the plates, and the voltage potential of the battery cells. For a battery to remain useful,
it must be able to produce high-amperage current over an extended period. A battery must also be able to accept
a charge, so that its voltage potential may be restored.

The battery is vented to release excess hydrogen gas that is created when the battery is being charged or dis-
charged. However, even with these vents, hydrogen gas can collect in or around the battery. If hydrogen gas is
exposed to flame or sparks, it may ignite. If the electrolyte level is low, the battery may arc internally and explode.
If the battery cell caps cannot be removed, the battery must be replaced if the electrolyte level becomes low.

BATTERY SYSTEM - SERVICE INFORMATION

8F - 9

DIAGNOSIS AND TESTING

BATTERY

The battery must be completely charged and the terminals should be properly cleaned and inspected before diag-
nostic procedures are performed. (Refer to 8 - ELECTRICAL/BATTERY SYSTEM - CLEANING) and (Refer to 8 -
ELECTRICAL/BATTERY SYSTEM - INSPECTION) for the proper battery cleaning and inspection procedures. (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY - STANDARD PROCEDURE - BATTERY CHARGING) for the
proper battery charging procedures.

MICRO 420 BATTERY TESTER

The Micro 420 automotive battery tester is designed to help diagnose the cause of an inoperative battery. (Refer to
8 - ELECTRICAL/BATTERY SYSTEM/BATTERY - STANDARD PROCEDURE - USING MICRO 420 BATTERY
TESTER) for instructions on the use of the Micro 420 battery tester.

WARNING: IF THE BATTERY SHOWS SIGNS OF FREEZING, LEAKING OR LOOSE POSTS, DO NOT TEST,
ASSIST-BOOST, OR CHARGE. THE BATTERY MAY ARC INTERNALLY AND EXPLODE. PERSONAL INJURY
AND/OR VEHICLE DAMAGE MAY RESULT.

WARNING: 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.

WARNING: 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.

A battery that will not accept a charge is inoperative, and must be replaced. Further testing is not required. A fully-
charged battery must be load tested to determine its cranking capacity. A battery that is fully-charged, but does not
pass the load test, is inoperative and must be replaced.

NOTE: Completely discharged batteries may take several hours to accept a charge. Refer to Standard Pro-
cedures for the proper battery charging procedures.

STANDARD PROCEDURE

BATTERY CHARGING

Battery charging is the means by which the battery can be restored to its full voltage potential. A battery is fully-
charged when:

•

Micro 420 electrical system tester indicates battery is OK.

•

All of the battery cells are gassing freely during battery charging.

•

Open-circuit voltage of the battery is 12.65 volts or above.

WARNING: NEVER EXCEED TWENTY AMPERES WHEN CHARGING A COLD (-1° C [30° F] OR LOWER) BAT-
TERY. THE BATTERY MAY ARC INTERNALLY AND EXPLODE. PERSONAL INJURY AND/OR VEHICLE DAM-
AGE MAY RESULT.

WARNING: IF THE BATTERY SHOWS SIGNS OF FREEZING, LEAKING, LOOSE POSTS, DO NOT TEST,
ASSIST-BOOST, OR CHARGE. THE BATTERY MAY ARC INTERNALLY AND EXPLODE. PERSONAL INJURY
AND/OR VEHICLE DAMAGE MAY RESULT.

WARNING: 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.

8F - 10

BATTERY SYSTEM - SERVICE INFORMATION

WARNING: IF THE BATTERY IS EQUIPPED WITH REMOVABLE CELL CAPS, BE CERTAIN THAT EACH OF
THE CELL CAPS IS IN PLACE AND TIGHT BEFORE THE BATTERY IS RETURNED TO SERVICE. PERSONAL
INJURY AND/OR VEHICLE DAMAGE MAY RESULT FROM LOOSE OR MISSING CELL CAPS.

CAUTION: Always disconnect and isolate the battery negative cable before charging a battery. Do not
exceed sixteen volts while charging a battery. Damage to the vehicle electrical system components may
result.

CAUTION: Battery electrolyte will bubble inside the battery case during normal battery charging. Electrolyte
boiling or being discharged from the battery vents indicates a battery overcharging condition. Immediately
reduce the charging rate or turn off the charger to evaluate the battery condition. Damage to the battery
may result from overcharging.

CAUTION: The battery should not be hot to the touch. If the battery feels hot to the touch, turn off the
charger and let the battery cool before continuing the charging operation. Damage to the battery may result.

After the battery has been charged to 12.65 volts or greater, perform a load test to determine the battery cranking
capacity, (Refer to 8 - ELECTRICAL/BATTERY SYSTEM/BATTERY - STANDARD PROCEDURE - USING MICRO
420 BATTERY TESTER) for the proper battery load test procedures. If the battery will endure a load test, return the
battery to service. If the battery will not endure a load test, it is inoperative and must be replaced.

Clean and inspect the battery hold downs, tray, terminals, posts, and top before completing battery service. (Refer
to 8 - ELECTRICAL/BATTERY SYSTEM - CLEANING) and (Refer to 8 - ELECTRICAL/BATTERY SYSTEM -
INSPECTION) for the proper battery system cleaning and inspection procedures.

CHARGING A COMPLETELY DISCHARGED BATTERY

The following procedure should be used to recharge a completely discharged battery. Unless this procedure is prop-
erly followed, a good battery may be needlessly replaced.

1. Measure the voltage at the battery posts with a voltmeter, accurate to 1/10 (0.10) volt. If the reading is below ten

volts, the battery charging current will be low. It could take some time before the battery accepts a current
greater than a few milliamperes. Such low current may not be detectable on the ammeters built into many battery
chargers.

2. Disconnect and isolate the battery negative cable. Connect the battery charger leads. Some battery chargers are

equipped with polarity-sensing circuitry. This circuitry protects the battery charger and the battery from being
damaged if they are improperly connected. If the battery state-of-charge is too low for the polarity-sensing cir-
cuitry to detect, the battery charger will not operate. This makes it appear that the battery will not accept charg-
ing current. See the instructions provided by the manufacturer of the battery charger for details on how to bypass
the polarity-sensing circuitry.

3. Battery chargers vary in the amount of voltage and current they provide. The amount of time required for a bat-

tery to accept measurable charging current at various voltages is shown in the Charge Rate Table. If the charg-
ing current is still not measurable at the end of the charging time, the battery is inoperative and must be
replaced. If the charging current is measurable during the charging time, the battery may be good and the charg-
ing should be completed in the normal manner.

CHARGE RATE TABLE

Voltage

Hours

16.0 volts maximum

up to 4 hours

14.0 to 15.9 volts

up to 8 hours

13.9 volts or less

up to 16 hours

BATTERY SYSTEM - SERVICE INFORMATION

8F - 11

Content .. 362 363 364 365 ..