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      04-03-2013, 03:17 PM   #17
mr_milo's Avatar

Drives: 2011 E93 328i
Join Date: Jan 2011
Location: SF Bay Area, CA

iTrader: (1)

Originally Posted by krhodes1 View Post
One thing to keep in mind, as part of their "Efficient Dynamics" program BMW does things a little differently with the charging system than most cars. They intentionally try to run the alternator as little as possible, the idea being that they then run it very hard while coasting or stopping. This saves gas - think of it as a very, very, very, very mild hybrid system. But I can see why short commutes can be a problem. Great theory, possibly not the best execution. There was a fascinating white paper on this floating around the forum a year or so back, but I can't find it now.

Note that this is also why there is the whole battery registration thing - the computer needs to know the state and what size/type the battery is so it doesn't go too far in that hard charging.
Thanks for the info. I started digging around and found out about that too. The BMW's Brake Energy Regeneration system apparently only charges the battery "when you take your foot from the accelerator or apply the brake", therefore even if you are driving the car it may not be charging the battery!

They even acknowledged that "today's vehicles require much more electrical energy than older models, due to the much wider array of electric and electronic on-board comfort and safety systems", yet they think allowing the generator to only be active at certain times somehow makes good sense????

Needless to say I'm disappointed in BMW.