Suzuki XL7 2007 Service Manual page 896

1J-3 Charging System:
The battery specification label, example below, contains information about the following:
• The test ratings
• The original equipment catalog number
• The recommended replacement model number
Battery Ratings
A battery may have 3 ratings:
• Amp hour
• Reserve capacity
• Cold cranking amperage
When a battery is replaced, use a battery with similar
ratings. Refer to the battery specification label on the
original battery or refer to "Battery Usage".
Amp Hour
The amp hour rating of a battery is the amount of time it
takes a fully charged battery, being discharged at a
constant rate of 1 amperes and a constant temperature
of 27°C (80°F), to reach a terminal voltage of 10.5 volts.
Refer to "Battery Usage" for the amp hour rating of the
original equipment battery.
Reserve Capacity
Reserve capacity is the amount of time in minutes it
takes a fully charged battery, being discharged at a
constant rate of 25 amperes and a constant temperature
of 27°C (80°F), to reach a terminal voltage of 10.5 volts.
Refer to "Battery Usage" for the reserve capacity rating
of the original equipment battery.
Cold Cranking Amperage
The cold cranking amperage is an indication of the ability
of the battery to crank the engine at cold temperatures.
The cold cranking amperage rating is the minimum
amperage the battery must maintain for 30 seconds at −
18°C (0°F) while maintaining at least 7.2 volts. Refer to
"Battery Usage" for the cold cranking amperage rating
for this vehicle.
Charging System Description and
Operation
Electrical Power Management (EPM) Overview
The electrical power management (EPM) system is
designed to monitor and control the charging system and
send diagnostic messages to alert the driver of possible
problems with the battery and generator. This EPM
system primarily utilizes existing on-board computer
capability to maximize the effectiveness of the generator,
to manage the load, improve battery state-of-charge and
life, and minimize the system's impact on fuel economy.
The EPM system performs 3 functions:
• It monitors the battery voltage and estimates the
battery condition.
• It takes corrective actions by boosting idle speeds,
and adjusting the regulated voltage.
• It performs diagnostics and driver notification.
The battery condition is estimated during ignition-off and
during ignition-on. During ignition-off the state-of-charge
(SOC) of the battery is determined by measuring the
open-circuit voltage. The SOC is a function of the acid
concentration and the internal resistance of the battery,
and is estimated by reading the battery open circuit
voltage when the battery has been at rest for several
hours.
The SOC can be used as a diagnostic tool to tell the
customer or the dealer the condition of the battery.
Throughout ignition-on, the algorithm continuously
estimates SOC based on adjusted net amp hours,
battery capacity, initial SOC, and temperature.
While running, the battery degree of discharge is
primarily determined by a battery current sensor, which
is integrated to obtain net amp hours.