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msw357 · Joined: 29 Jun 2006 Posts: 13 Location: San Diego

Hi All,
Just starting having a battery issue on the 850. So, went out and had the existing battery replaced with a new batt. Interstate is the brand, as the old one did have some warranty left. I have only owned the car since last August and it has been trouble-free until lately. Any commonly known issue on 8 series cars with battery life? I don't drive it alot, but if I let it set for more than 2 days, the battery is dead! Any ideas would be appreciated! Thanks

edjack · Joined: 04 Feb 2002 Posts: 3887 Location: San Jose, CA

One of the electronic subsystems is not going to sleep. You'll need to monitor the battery current as you pull fuses of the different subsystems.

Is your HVAC blower erratic? If so, the cause of the battery drain may be the final stage resistor.
_________________

Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.

msw357 · Joined: 29 Jun 2006 Posts: 13 Location: San Diego

Thanks for the tip. It was actually the second battery that is on the passenger side that was draining the new one down. It still had some warranty remaining, so Interstate changed it out for $40. Now its all good. Thanks for your help.

Mark

edjack · Joined: 04 Feb 2002 Posts: 3887 Location: San Jose, CA

Aha! I didn't know that the 850 has 2 batteries. If they are in parallel, you must replace them together.
_________________

Ed BMW CCA member since 1987 (Nr. 62319).
'97 540i 6 speed Aspensilber over Aubergine interior.

msw357 · Joined: 29 Jun 2006 Posts: 13 Location: San Diego

I found out the hard way! But, now I know. The 850 has a lot of features that others do not have. 2 batteries is one of them. 12 cylinders is another! Thanks again.

Mark