There is a known battery drain issue. My new in May 2007 X4 4.8 is on its third battery and has died twice. Once without any control message. There is a parasitic battery drain that is not constant but will kill the battery over time. If it is the case with my SUV it has to be in others. It is not a driving issue, blue tooth or any other excuse. The problem is my SUV has been in service since Feb 8th and the dealer and BMWNA can not isolate it so bottom line there is an issue but they do not know what it is so no idea how to fix it. Just keep records as you may well need to take other actions