Charging System: Description and Operation

CHARGING SYSTEM DESCRIPTION AND OPERATION

GENERATOR
The generator features the following major components:
- The delta stator
- The rectifier bridge
- The rotor with slip rings and brushes
- A conventional pulley
- Dual internal fans
- The regulator

The pulley and the fan cool the slip ring and the frame.

The generator features permanently lubricated bearings. Service should only include tightening of mount components. Otherwise, replace the generator as a complete unit.

REGULATOR
The voltage regulator controls the rotor field current in order to limit the system voltage. When the field current is on, the regulator switches the current on and off at a rate of 400 cycles per second in order to perform the following functions:
- Radio noise control
- Obtain the correct average current needed for proper system voltage control

At high speeds, the on-time may be 10 percent with the off-time at 90 percent. At low speeds, the on-time may be 90 percent and the off-time 10 percent.

REGULATED VOLTAGE CONTROL (RVC)
The LY7 engine comes equipped with GEN II regulated voltage control (RVC). RVC is used to more accurately control the amount of voltage put into the battery based upon the battery state of charge (SOC) and battery temperature.

The main components of the RVC system is a new voltage regulator, dash integration module (DIM), and the engine control module (ECM).
- Voltage regulator-Uses a pulse width modulation (PWM) signal on the generator L-terminal circuit instead of a 5-volt reference signal from the ECM to determine voltage output of the generator.
- ECM-Controls the PWM signal to the regulator and provides diagnostics for the generator L-terminal and generator F-terminal. It also provides feedback of the generator F-terminal to the DIM for its calculations.
- DIM-Calculates an estimate of the battery SOC and battery temperature based upon, battery voltage and internal calibrations.

When the DIM has determined what voltage the battery should receive, a message is sent to the ECM. This message tells the ECM what percentage to set the PWM signal at.

With RVC in closed loop control of the generator, it can vary the voltage at the battery from 13.4 volts, battery temperature above 70°C (158°F) and battery SOC 95 percent or higher, to 14.9 volts, battery temperature below -30°C (-22°F) and battery SOC 65 percent or lower. If RVC looses control of the generator because of a failure the voltage regulator will default to 13.9 volts at the battery and function as a normal generator.

CIRCUIT DESCRIPTION
The generator provides voltage to operate the vehicle electrical system and to charge its battery. A magnetic field is created when current flows through the rotor. This field rotates as the rotor is driven by the engine, creating an AC voltage in the stator windings. The AC voltage is converted to DC by the rectifier bridge and is supplied to the electrical system at the battery terminal.

When the engine is running, the engine control module (ECM) sends a pulse width modulation (PWM) signal to the voltage regulator. The generator's voltage regulator then controls the current to the rotor according to the PWM signal received, thereby controlling the output voltage. The rotor current is proportional to the electrical pulse width supplied by the regulator. The PWM signal may vary between 12-88 percent. The lower the PWM signal percentage the lower the generator voltage output will be. Below 12 percent and above 88 percent the voltage regulator defaults to 13.9 volts. This generator is self starting and does not require voltage on the L-terminal circuit to initiate battery charging. This also means that the generator cannot be commanded OFF with the scan tool. When the voltage regulator detects a charging system problem, it grounds the generator L-terminal circuit to signal the ECM that a problem exists. The ECM also monitors the generator field duty cycle signal circuit for failures.

CHARGING SYSTEM INDICATORS
The instrument panel cluster (IPC) illuminates the charge indicator when the following occurs:
- The engine control module (ECM)/powertrain control module (PCM) detects that the generator output is less than 11 volts or greater than 16 volts. The IPC receives a class 2 message from the ECM/PCM requesting illumination.
- The IPC determines that the system voltage is less than 11 volts or greater than 16 volts. The IPC receives a class 2 message from the dash integration module (DIM) indicating the system voltage.
- The IPC performs the displays test at the start of each ignition cycle. The indicator illuminates for approximately 3 seconds.

BATTERY NOT CHARGING - 7
The IPC illuminates the BATTERY NOT CHARGING - 7 indicator in the driver information center (DIC) when the ECM/PCM detects a malfunction with the generator output. The IPC receives a class 2 message from the ECM/PCM requesting illumination.

BATTERY SAVER ACTIVE - 27
The IPC illuminates the BATTERY SAVER ACTIVE - 27 indicator in the DIC when the DIM reduces or disables the performance of some vehicle systems in order to reduce the load on the charging system. The IPC receives a class 2 message from the DIM requesting illumination.

BATTERY VOLTAGE HIGH - 8
The IPC illuminates the BATTERY VOLTAGE HIGH - 8 indicator in the DIC when the IPC determines that the system voltage is greater than 16 volts. The IPC receives a class 2 message from the DIM indicating the system voltage.

BATTERY VOLTAGE LOW - 6
The IPC illuminates the BATTERY VOLTAGE LOW - 6 indicator in the DIC when the IPC determines that the system voltage is less than 11 volts. The IPC receives a class 2 message from the DIM indicating the system voltage.

SERVICE CHARGING SYS - 102
The IPC illuminates the SERVICE CHARGING SYS - 102 indicator in the DIC when the PCM/ECM detects a malfunction with the generator output. The IPC receives a class 2 message from the PCM/ECM requesting illumination.