About the electrical system... hmmm... sounds like a recall in waiting to me at some point... what's the std battery capacity on the X35d? Its either too small of a battery or problems w/alternator and/or very varied electrical system usage which can kill a battery. I've done that w/my 528 several times. I have a custom sound system w/1.5kW RMS power and sometimes like to "punch it" ... I've gone through about 3 batteries over the past ~5 years. It could also be something just draining the battery while the engine's off - again need a larger battery or the system (car) needs to make sure all is OFF when the engine is not turning.

Good thing I still have a BMW Battery Tender I had my bike hooked up to when parked and un-ridden for years

spacey