I also have a '07 4.8 that is heavily loaded with electronic options. I had the same high battery drain that others have reported. The dealer has recoded it and gave me a trickle charger because they thought I wasn't driving enough. However, I read in the other thread that someone recommended that locking the doors every time solved a similar problem in a Mercedes S class. Since I started locking the car every time I park it (even in my garage at night), I have never had the high battery drain again. I'm now going on 12 months without a recurrence of the problem.

Although I am not certain this fixed it (could be coincidence), I did notice that if the X is parked and unlocked, it periodically makes electronic sounds. It doesn't do this when it is locked, which makes me believe that when it is unlocked, there is some program that runs to periodically check systems.

It can't hurt to try.

PS: My M3 or 335 doesn't seem to have this problem but now I lock the M3 all the time too.

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2012 F10 550xi Carbon black/oyster
2011 E92 M3 SSII/black
2012 W166 ML63 Steel grey/porcelain
2007 E93 monaco blue/beige (retired)
2010 E70 35d Space grey/saddle brown (retired)