to do w/the "37 degree warning tone" on the out.side temp guage deal. Suspect the OBC didn't fully turn off, and even parked and "off",when the ambient temp got <40, '37', the OBC monster, and it is a Freaking Monster, woke up and the radio on deal was simply a default and drained the batt. Sorry for the Long sentence. Thought I was back in the U! :) BMWNA guy didn't disagree w/observation/hypothesis.