| Description and Operation 'Smart charge' generator control system General The generator creates electrical current to supply the vehicle electrical system and maintain the battery in a charged condition. The generator is driven by the accessory drive belt.
For additional information, refer to: Accessory Drive (303-05 Accessory Drive, Description and Operation) /
Accessory Drive - 1.6L (303-05, Description and Operation).
When the engine is started, the generator begins to generate alternating current (AC) which it converts to direct current (DC) internally. The DC current is supplied to the battery and vehicle electrical loads at a voltage controlled by the voltage regulator (located on the back of the generator). The charging system voltage is controlled by the powertrain control module (PCM). The battery is more efficiently charged with a higher voltage when the battery is cold and a lower voltage when the battery is warm. The PCM is able to adjust the charging voltage according to battery temperature, which it calculates based on intake air temperature (IAT) and engine coolant temperature (ECT). The PCM simultaneously monitors and controls the voltage output of the generator. When the current consumption is high or the battery is excessively discharged, the system is able to increase the idle speed. To minimize the engine drag when starting the engine, the PCM deactivates the generator. When the engine has started, the PCM then progressively increases the output of the generator. The PCM controls the operation of the charging system warning indicator which is located in the instrument cluster. The PCM is therefore responsible for turning the warning indicator off after the engine is started and illuminating it under fault conditions, the warning indicator will also be illuminated by the PCM at key–on, engin-off, and stall conditions. The smart charging system consists of the following functions: - Battery temperature estimation and charging voltage control
- Generator load feed forward
- Generator deactivation during engine crank
- Idle speed increase under low voltage / high electrical load conditions (to increase alternator output and reduce battery discharge)
- Low voltage electrical load deactivation
- Over-voltage activation of electrical loads
By continually calculating the battery temperature and controlling generator output voltage the battery charging current is optimized. The generator load feed forward function gives the PCM advance warning of impending electrical load, and hence impending changes in alternator torque. Using this information, the PCM is able to achieve a greater degree of idle stability. The PCM also controls the generator activation during crank, and the idle speed increase functions. The passenger junction box (PJB) controls the two remaining smart charging functions, low voltage electrical load deactivation and over-voltage activation of electrical loads. When the battery voltage drops below the low voltage threshold, the PJB disables the following components in this order with a 5 second delay between each load deactivation: - Heated windshield
- Heated rear window
- Air conditioning
The PJB re-enables all previously disabled electrical loads when the battery voltage is above the low voltage threshold. The order for re-enabling loads is air conditioning, then the heated rear window, then the heated windshield, with a 5 second delay between each load reactivation. When re-enabled, the electrical loads are returned to normal mode, therefore the component is switched off awaiting a PJB input signal from the switch. Over-voltage activation of electrical loads is enabled when the PJB recognizes the battery voltage is above the over-voltage threshold for a 20 second period, and the charging system warning indicator is on. When the threshold is reached the PJB activates the following components in this order with a 5 second delay between each load: - Heated rear window
- Heated windshield
The purpose of this is to reduce the voltage back within specification, and reduce any overcharging damage to the battery. The PJB returns the electrical loads to normal mode if the battery voltage drops below the high voltage threshold for a 20 second period. This is in order to prevent excessive battery drain. The order for returning loads to normal mode is heated windshield then heated rear window, with a 5 second delay between each load reactivation. A cycling condition may occur where loads are repeatedly activated and deactivated as the voltage levels increase and decrease. This behavior is to be expected in a continuous over-voltage fault condition, and serves to minimize both damage to the battery due to overcharging, and the battery current drain due to activation of the heated rear window and heated windshield. In normal mode, the electrical loads are switched off awaiting a PJB input signal from the switch. The low voltage threshold is approximately 10.3 volts and the over-voltage threshold is approximately 16 volts. Schematic of the 'Smart charge' generator control system 2 - Battery voltage sensing line 4 - Battery junction box (BJB) 5 - Generator required output signal from the PCM 8 - Generator operation monitoring signal to the PCM Starting the generator during engine starting In the "smart charge" generator control system", the generator is deactivated during engine starting. The generator is only switched on after the engine has started. Switching on is done electronically by the PCM. The generator power is then increased smoothly to the value required. Increased idle speed At idle with high generator load, the idle speed is increased in order to increase the generator power. The system can increase the idle speed in steps by up to 150 rev/min above the base idle speed. Diagnosis There is a self-test facility for the Smart Charge System, stored in the PCM and which can be accessed through the WDS. If a fault occurs in the system, the charging system warning indicator is illuminated by the PCM. If voltage regulation fails, the generator operates with a fixed charging voltage of approximately 13.5 Volts. With fixed charging voltage the generator operates as usual and still delivers enough current for the vehicle systems. After the ignition is switched on, the PCM switches on the charging system warning indicator to check that it operates. After the engine starts the charging system warning indicator is switched off again. During the engine run condition, the charging system warning indicator will only illuminate if the PCM identifies that there is a fault present for a 20 second period. (Voltage out of range, internal generator fault, or PCM to generator communication fault). | 
