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30FF <3
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2,619 Posts
could be a couple things..

lose cables, bad VR (behind the alt), bad ground/power etc....

first thing is to, get the battery checked out which you did, if it passed, then I would read codes via INPA/Carly if you have it.

If not you could test your alternator at a local autozone, either by taking it out or use their battery tester...

Also make sure you dont have any extra things in the car that could be plugged up thats causing your battery drain.

Another easy step is to, see what your voltages are while driving the car, remember the battery is only attended to start the car, not keep it running, so if you have weird voltages drop while driving, it could be your alternator.
 

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1,157 Posts
remember the battery is only attended to start the car, not keep it running, so if you have weird voltages drop while driving, it could be your alternator.

If that were true modern cars would not need the size of batteries that they have in them. Will the car run after it is started with the battery removed? Sure. Will the car function as designed with the engine running and the battery removed? No
 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 99K miles NOKIAN WR G3 12K miles
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17,471 Posts
Closed-circuit current measurement

I drive a 2009 535i I recently got a increased battery discharge message and tested the battery could it possible be the alternator?
Increased battery discharge warnings HAVE NOTHING TO DO WITH THE GD BATTERY!

Increased discharge warnings are caused by excessive / unauthorized current from the battery while the car is off and not charging. Causes are a module not sleeping properly, a module being wakened too often or an improperly powered accessory.

https://www.newtis.info/tisv2/a/en/...hicle-electrical-system/61-20-battery/YDj5gs8
 
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