NGBSDG BSD interface to alternator: Identification
WARNING: This page is about a different car, the 2013 BMW X5, 2012 BMW X5, and 2011 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
The above-cited calculation of an alternator's torque and of the proportion of this alternator's capacity being used display substantial variations according to the type (output) and manufacturer.
This is why the engine-management control unit receives these data from the alternator. The engine-management control unit adapts its calculations and operational specifications to the precise type.