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Discussion Starter #1
Hey guys,

I'm kinda stuck with a one year old problem that's eating batteries like cookies. I kept having problems starting the car after parking it 8-10 hours which let to numerous dealer and self troubleshoots, new batteries, new fan relays, current drain tests etc...

Long story short, I just purchased a new battery since the old one was nuked due to several discharges.

- New battery's voltage at the shop was 12.62v and the 'eye' was green.
- New battery with the car turned on shows 14.2 - 14.6v thus alternator/charing system should be OK.
- New Battery voltage after a 10-15min drive is 12.6v (12.72 sometimes, 12.8v)
- I Hooked up an meter in series and checked the drain which was at around 3A then after 15 minutes it was 0.02A both with the alarm on and with the alarm off. I glanced at it several times over the course of 2-3 hours and it seemed to stay around the 0.02-0.03A range.
- Sometimes while the car is parked armed, the alarm still randomly goes off.
- After parking 8-10 hours, the battery shows around 12.5v, slightly lower than a full charge.

All this leads me to believe there's an intermittent problem that wakes the car *sometimes* and that's slowly eating the battery. In case the drive wasn't long enough to full charge the battery, the battery can drain during the time that it's sitting parked. After a couple discharges the battery is as good as dead.

My hope is to not drain this brand new batt. Any troubleshooting suggestions? I'm thinking pulling 1 fuse per night and seeing if in the AM there's a lower voltage than in the evening. Can you suggest which fuses are the common culprits that I should start with?
 

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This has only ocurred to someone I know that was a "person of interest" in the eyes of the law.
Police place bugging, tracking and monitoring devices in the vehicle that often drain batteries.
Only you or a PO might know if this is a possibility.

Otherwise I have no other idea
 

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Discussion Starter #3
Hmm yeah I doubt it's something like that. Such a device would drain extra current at all times, not really intermittent I would think. When the car sleeps it's at 0.02A as long as I could watch it.
 

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It can be intermittent.
Remote activation.
GPS input for activation.
Voice activation.
Stationary activation.
Timed activation.
Random activation.

Don't ask me how I know.
Have you had any indicator bulbs fail?
 

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Check the usual like your final stage?

Have a meter that makes an audible alert if it goes over a set range? (i.e. 0.02A)

I would start with pulling fuses of main components that are unneccessary, like the NAV, IHKE, etc.

Another thing to consider but I don't have a lot of information on right now is that there was something somewhere once when I worked at BMW that talked about a certain component waking the CAN bus randomly. I don't remember exactly what it was but for some reason I think it was due to a faulty Nav computer.
 

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I can relate to the battery drain and random activation of the alarm. Sometimes i could hear it going off in the garage in the middle of the night. I exhausted all of the normal drain possisbilities..The only code the car was throwing was a lock actuator malfunction, I replaced this, and the power drain hasnt happened since....just my .02
 

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Discussion Starter #7 (Edited)
It can be intermittent.
Have you had any indicator bulbs fail?
AussieM, Sometimes the hazards (turnsignals) flash and sometimes they don't on disarming the alarm randomly.

Verruckt, The FSU was checked as faulty and already replaced by the dealer. I've had several battery failures after that.

lehigh_guy, do you recall the code? Did you check the code yourself or did you take it to the dealer to have them look at it? The car was there overnight and they 'didn't find anything wrong'.
 
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