General information
The powertrain control module (PCM) controls the alternator charging voltage. The connection between the PCM and the generator is made via the control module subnetwork (LIN) bus.
If the load on the alternator is high, the PCM can increase the idle speed.
The alternator is temporarily deactivated during engine starting so that the engine drag moment is minimized and it is reactivated again after the starting procedure.
The PCM controls the charge control lamp in the instrument cluster via the controller area network (CAN) bus.
Smart Charge system
In addition to the familiar functions, the Smart Charge system also performs the following functions:
The battery charging current is optimized through continuous calculation of the battery temperature and monitoring of the alternator output voltage.
By receiving the forwarded alternator load signal, the PCM is given early warning whenever an electric consumer is switched on or off. This means that the PCM receives information about imminent changes in the torque drawn by the alternator. By evaluating this information the PCM can provide a higher level of idling stability.
The two remaining functions of the Smart Charge System are controlled by the GEM.
Electrical consumers are switched off due to low voltage when the GEM determines (on the basis of the message received from the PCM on the CAN bus via the instrument cluster) that the battery voltage has dropped below the threshold.
When the threshold for low battery voltage is reached the GEM automatically deactivates the following consumers - in this order and with a gap of 5 seconds between each:
If the battery voltage rises back above the lower threshold then the GEM re-enables all of the electrical consumers which were previously disabled. They then have switched off status and must be switched back on by the driver.
Electrical consumers are switched on due to excessively high voltage if the GEM determines that the battery voltage is above the threshold for overvoltage and the charge control lamp has been switched on.
When the threshold is reached the GEM automatically activates the following consumers - in this order and with a gap of 5 seconds between each:
If the battery voltage drops back below the threshold then the GEM automatically deactivates any consumers that were switched on. However, if they were switched on by the driver before the automatic activation, they will then be switched on again in turn with a 5-second time interval.