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Old 01-29-2013, 12:03 PM
jadnashuanh jadnashuanh is offline
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Location: NH
Join Date: Jun 2011
Posts: 1,571
Mein Auto: 535ix-drive GT; i3 BEV
The alternator has a clutch similar to an a/c compressor on this vehicle. The computer only activates the alternator when it wants (or needs?) to, otherwise, it's just freewheeling. My question is when does it actually engage the clutch to charge the battery? I know it is doing it when the dash indicator says, but cruising down the interstate, I've never seen that come on. I have seen it come on once when coasting down a long hill and at the same time, while on cruise, it downshifted to keep the car from exceeding the setpoint (which surprised me!). That's only happened once, but I don't go that way often, and then, can only use the cruise when there's not much traffic.

Well, to be honest, on an alternator, they could control it by adjusting the field current, but I think I remember reading somewhere that it has a clutch.

Last edited by jadnashuanh; 01-29-2013 at 12:04 PM.
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