Happened to us during the winter. Had the battery checked 3 times and the diagnostic kept returning 'Unfavorable driver profile' or some-such. The service rep told us we did not do enough long drives for the battery to keep its charge, which was obviously BS since we had the car for 1.5 years before it happened and our driving habbits stayed the same for that time.
Finally, the third time we took it in, the battery failed a stresstest and they put in a new one. Fixed the problem.
I heard that BMW may have changed the type of battery used in production and that changing to the new type of battery will take a reprogram of car. Can't really tell if that is true but our car was reprogrammed in the process of getting a new battery.
Held og lykke - haaber du finder ud af hvad problemet er
