Silverado 1500 2WD V8-6.0L Hybrid (2009)
Charging System: Description and Operation
Charging System Description and Operation
12-Volt Battery
The following information is for the 12-Volt battery only.
For information about charging the high voltage drive motor batteries, refer toJump Assist Description and Operation (See: Hybrid Drive
Systems/Battery System, Hybrid Drive/Description and Operation/Jump Assist) .
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. This EPM system primarily utilizes existing on-board computer capability to maximize the effectiveness of the charging system,
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:
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It monitors the battery voltage and estimates the battery condition.
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It takes corrective actions by adjusting the regulated voltage.
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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.
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.
Charging System Components
Drive Motor/Generators
The drive motor/generators are serviceable components located within the transmission housing. When the rotors are spun, an alternating current (AC) is
induced into the stator windings. This AC voltage is then sent to the drive motor generator power inverter module (PIM) where it is converted to high
voltage direct current (DC) power. The output of the PIM is converted into low voltage electrical power by the accessory DC power converter module
(APM) for use by the vehicle's electrical system to maintain electrical loads and battery charge.
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 desired voltage set point and sends the information to the APM. The BCM
monitors a battery current sensor, the battery positive voltage circuit, and estimated battery temperature to determine battery state of charge (SOC).
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 receives control decisions based on messages from 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.
