[richardodn]

Might as well follow up with an explanation of how the system actually works. The BMW smart charging system tries to keep the battery at a specific state of charge that is less than 100%. For the sake of this explanation, let's say that value is 80%. I don't know what the actual value is. The alternator is capable of varying it's charging load on the engine. The higher the charge rate, the higher the engine load.

The basic idea is to convert the kinetic energy of the vehicle to energy stored in the battery. So when the car is slowing down or braking, it can up the charging load and charge the battery above it's target charge state. Now you've converted kinetic energy to battery energy. Now that the battery is above its target, the alternator can ignore charge requests at non-optimal times.