Regulation

Regulation

The alternator communicates with the Engine Control Module (ECM) via the BSD (bit-serial data interface). The alternator conveys data such as model and manufacturer. This is necessary to allow the engine management system to adapt it's calculations and specific control to the type of alternator fitted.

The ECM takes on the following functions:

- Activation/deactivation of the alternator.
- Informing the alternator regulator of the nominal voltage value to be set.
- Controlling the alternator's response to load.
- Diagnosing the data line between the alternator and the ECM.
- Storing alternator fault codes.
- Activating the charge indicator lamp in the instrument cluster.

The connection with the ECM makes it possible to equalize the alternator load torque for nearly all operating conditions. This supports the engine idling speed control and the battery load balance. In addition, the ECM receives information from the Power Module about the battery's calculated temperature and charge status. This means that alternator output can be adapted precisely to the temperature and load status of the battery which increases the battery service life.

The charge indicator display strategy has not changed in comparison with the alternators currently in use. Regulating the alternator output is particularly important when activating Valvetronic operating motors.

A temperature protection function is implemented in the voltage regulator. If the alternator overheats, the alternator voltage is reduced until an appropriate temperature has been reached.

The ECM can recognize the following faults:

- Mechanical faults such as blockages or belt drive failure.
- Electrical faults such as exciter diode defects or over/under voltage caused by regulation defects.
- Connection defects between the ECM and the alternator.

Coil breaks and short-circuits cannot be recognized. The basic alternator function is in operation even if the BSD interface fails.


NOTE: The alternator regulator voltage is influenced by the ECM - BSD interface. The battery charge voltage can therefore be up to 15.5 V, depending on the battery temperature. If a battery charge voltage of up to 15.5 V is measured, the regulator is not faulty. A high charge voltage indicates a low battery temperature.