Battery Size And Ratings; Battery Operation - Jeep Cherokee 2000 Service Manual

8A - 2 BATTERY
DESCRIPTION AND OPERATION (Continued)
ing against one another. These dissimilar metal
plates are submerged in a sulfuric acid and water
solution called an electrolyte.
The factory-installed battery has a built-in test
indicator (hydrometer). The color visible in the sight
glass of the indicator will reveal the battery condi-
tion. For more information on the use of the built-in
test indicator, refer to Battery in the index of this
service manual for the location of the proper battery
diagnosis and testing procedures. The factory-in-
stalled low-maintenance battery has removable
battery cell caps. Water can be added to this bat-
tery. The battery is not sealed and has vent holes in
the cell caps. The chemical composition of the metal
coated plates within the low-maintenance battery
reduces battery gassing and water loss, at normal
charge and discharge rates. Therefore, the battery
should not require additional water in normal ser-
vice. If the electrolyte level in this battery does
become low, water must be added. However, rapid
loss of electrolyte can be caused by an overcharging
condition. Be certain to diagnose the charging system
after replenishing the water in the battery for a low
electrolyte condition and before returning the vehicle
to service. Refer to Charging System in the index of
this service manual for the location of the proper
charging system diagnosis and testing procedures.
For battery maintenance schedules and jump start-
ing procedures, see the owner's manual in the vehicle
glove box. Optionally, refer to Maintenance Sched-
ules and Jump Starting, Towing and Hoisting in
the index of this service manual for the location of
the recommended battery maintenance schedules and
the proper battery jump starting procedures. While
battery charging can be considered a maintenance
procedure, the battery charging procedures and infor-
mation are located in the service procedures section
of this service manual. This was done because the
battery must be fully-charged before any battery
diagnosis or testing procedures can be performed.
Refer to Battery Charging in the index of this ser-
vice manual for the location of the proper battery
charging procedures.
NOTE: This group covers both Left-Hand Drive
(LHD) and Right-Hand Drive (RHD) versions of this
model. Whenever required and feasible, the RHD
versions of affected vehicle components have been
constructed as mirror-image of the LHD versions.
While most of the illustrations used in this group
represent only the LHD version, the diagnostic and
service procedures outlined can generally be
applied to either version. Exceptions to this rule
have been clearly identified as LHD or RHD, if a
special illustration or procedure is required.

BATTERY SIZE AND RATINGS

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
Battery in the index of this service manual for the
location of the proper factory-installed battery speci-
fications. Battery sizes and ratings are discussed in
more detail below.
• Group Size
The outside dimensions and terminal placement of
the battery conform to standards established by the
Battery Council International (BCI). Each battery is
assigned a BCI Group Size number to help identify a
correctly-sized replacement.
• Cold Cranking Amperage
The Cold Cranking Amperage (CCA) rating specifies
how much current (in amperes) the battery can
deliver for thirty seconds at -18° C (0° F). Terminal
voltage must not fall below 7.2 volts during or after
the thirty second discharge period. The CCA required
is generally higher as engine displacement increases,
depending also upon the starter current draw
requirements.
• Reserve Capacity
The Reserve Capacity (RC) rating specifies the time
(in minutes) it takes for battery terminal voltage to
fall below 10.5 volts, at a discharge rate of 25
amperes. RC is determined with the battery fully-
charged at 26.7° C (80° F). This rating estimates how
long the battery might last after a charging system
failure, under minimum electrical load.
• Ampere-Hours
The Ampere-Hours (AH) rating specifies the current
(in amperes) that a battery can deliver steadily for
twenty hours, with the voltage in the battery not fall-
ing below 10.5 volts. This rating is also sometimes
identified as the twenty-hour discharge rating.
OPERATION
When an electrical load is applied to the terminals
of the battery, an electrochemical reaction occurs.
This reaction causes the battery to discharge electri-
cal current from its terminals. As the battery dis-
charges, 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 sulfate. At the same
time, oxygen from the positive plate material com-
bines with hydrogen from the sulfuric acid, causing
the electrolyte to become mainly water. The chemical
changes within the battery are caused by the move-
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