Suzuki XL7 2007 Service Manual page 897

In addition, the EPM function is designed to perform
regulated voltage control (RVC) to improve battery SOC,
battery life, and fuel economy. This is accomplished by
using knowledge of the battery SOC and temperature to
set the charging voltage to an optimum battery voltage
level for recharging without detriment to battery life.
The Charging System Description and Operation is
divided into 3 sections. The first section describes the
charging system components and their integration into
the EPM. The second section describes charging
system operation. The third section describes the
instrument panel cluster (IPC) operation of the charge
indicator, driver information center (DIC) messages, and
voltmeter operation.
Charging System Components
Generator
The generator is a serviceable component. If there is a
diagnosed failure of the generator it must be replaced as
an assembly. The engine drive belt drives the generator.
When the rotor is spun it induces an alternating current
(AC) into the stator windings. The AC voltage is then
sent through a series of diodes for rectification. The
rectified voltage has been converted into a direct current
(DC) for use by the vehicles electrical system to maintain
electrical loads and the battery charge. The voltage
regulator integral to the generator controls the output of
the generator. It is not serviceable. The voltage regulator
controls the amount of current provided to the rotor. If
the generator has field control circuit failure, the
generator defaults to an output voltage of 13.8 volts.
Body Control Module (BCM)
The body control module (BCM) is a GMLAN device. It
communicates with the engine control module (ECM)
and the instrument panel cluster (IPC) for electrical
power management (EPM) operation. The BCM
determines the output of the generator and sends the
information to the ECM for control of the generator field
control circuit. It monitors the generator field duty cycle
signal circuit information sent from the ECM for control of
the generator. It monitors a battery current sensor, the
battery positive voltage circuit, and estimated battery
temperature to determine battery state of charge (SOC).
The BCM performs idle boost.
Battery Current Sensor
The battery current sensor is a serviceable component
that is connected to the negative battery cable at the
battery. The battery current sensor is a 3-wire hall effect
current sensor. The battery current sensor monitors the
battery current. It directly inputs to the BCM. It creates a
5-volt pulse width modulation (PWM) signal of 128 Hz
with a duty cycle of 0-100 percent. Normal duty cycle is
between 5-95 percent. Between 0-5 percent and 95-100
percent are for diagnostic purposes.
Engine Control Module (ECM)
The ECM directly controls the generator field control
circuit input to the generator. The ECM receives control
decisions based on messages from the BCM. It monitors
the generators generator field duty cycle signal circuit
and sends the information to the BCM.
Instrument Panel Cluster (IPC)
The IPC provides a means of customer notification in
case of a failure and a voltmeter. There are 2 means of
notification, a charge indicator and a driver information
center (DIC) message of SERVICE BATTERY
CHARGING SYSTEM.
Charging System Operation
The purpose of the charging system is to maintain the
battery charge and vehicle loads. There are 6 modes of
operation and they include:
• Battery Sulfation Mode
• Charge Mode
• Fuel Economy Mode
• Headlamp Mode
• Start Up Mode
• Voltage Reduction Mode
The engine control module (ECM) controls the generator
through the generator field control circuit. It monitors the
generator performance though the generator field duty
cycle signal circuit. The ECM controls the generator
through the generator field control circuit. The signal is a
5-volt pulse width modulation (PWM) signal of 128 Hz
with a duty cycle of 0-100 percent. Normal duty cycle is
between 5-95 percent. Between 0-5 percent and 95-100
percent are for diagnostic purposes. The following table
shows the commanded duty cycle and output voltage of
the generator:
Commanded Duty Cycle
10%
20%
30%
40%
50%
60%
70%
80%
90%
The generator provides a feedback signal of the
generator voltage output through the generator field duty
cycle signal circuit to the ECM. This information is sent
to the body control module (BCM). The signal is a 5-volt
PWM signal of 128 Hz with a duty cycle of 0-100
percent. Normal duty cycle is between 5-99 percent.
Between 0-5 percent and 100 percent are for diagnostic
purposes.
Charging System: 1J-4
Generator Output
Voltage
11 V
11.56 V
12.12 V
12.68 V
13.25 V
13.81 V
14.37 V
14.94 V
15.5 V