I want tho keep the batteries to my 840ci 1995, charged charged through the winter but don't plan on driving it very often. BMW sold me a bmw advanced battery charger that plug from the wall to the cigarette lighter in my car, however i think it will not work because the car has two batteries and it will false peak the charge. can I use this charger or do i need to do something else?

It will work. The 2 batteries are in Parallel connection. However, I use a trickle charger and connect the underhood battery posts.

cool, thanks for your help. I was hoping I would not have to take this thing back and they said that once it is opened it is not returnable.