Originally Posted by wadny
I've been having the same problem with my 2011 135i, which was bought in April of 2010, so the battery is 2 1/2 years old now. My dealer also said they get a lot of complaints about this from people who don't drive the cars a lot (I have 17k miles on mine, but haven't been driving as much since I retired in May of 2012). My previous car was a 2002 330i, and it still had the original battery when I sold it in 2010. I guess it's time for the trickle charger.
When I first called my dealer about this problem, on a 15 degree day during the fourth winter I had the car, I told him my clock and my heater shut down when I drove the car that day. He immediately said "I bet you don't drive your car very much. The car makes a lot of demands on the battery, including when the car is not being driven, so the charge can run low with infrequent use and the problem shows up especially on cold days".
Now it is the fifth winter and the problem has become chronic if I don't use the trickle charger.
I assume the problem is just an aging battery, but I am buying an Equus 3721 Battery and Charging System Monitor
at Amazon to see if I can assure myself the charging system is still trying to charge the battery properly when I am driving the car.
This voltmeter just plugs into the cigarette lighter, so I am hoping it will not screw up any of my 135i's sensitive computer chip-controlled electric circuits.