BMS and charging
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AudiWorld Member
Joined: Apr 2023
Posts: 123
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BMS and charging
quick sanity check and guidance. I took the S8 in to get the windows tinted. While there they hooked up a charger to positive and negative battery posts not the grounding post. When I went to pick up the car after it had been sitting for an hour or two it was no start and click instead of crank for one time and then the car was completely dead with no lights at all and really low battery voltage 2.3v. I disconnected the battery until I could come back with VCDS and check everything. Car sat overnight and battery had recovered to 10.1V so hopefully not ruined. Connected negative battery cable and voltage dropped as expected systems came on but no start no crank as expected.I jumped it properly to get it home and it is on charge now. Question I have is did they break my BMS and is there a 100% certain way to test it? Or is it ok to charge direct via battery which I don't think is the case
AudiWorld Wiseguy
Joined: Aug 2012
Posts: 4,071
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From: Chicago
Oh jeez, this old chestnut again. Why was a window tint place hooking up a battery charger? WTF were they doing?
Anyway, they’ve blown the battery management module by connecting direct to -ve battery terminal, and not the jumper post.
Read the user manual and/or google to find out the proper way to do it.
Anyway, they’ve blown the battery management module by connecting direct to -ve battery terminal, and not the jumper post.
Read the user manual and/or google to find out the proper way to do it.
Thread Starter
AudiWorld Member
Joined: Apr 2023
Posts: 123
Likes: 10
Yeah I went oh F! As soon as I popped the trunk and saw the battery compartment open. I knew what had happened. I was just hoping a charger wasn't enough to blow it.
Last edited by zen beer; Jun 17, 2026 at 07:25 PM.
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