they charge through the ignition,,,,, this means that the charger in the ignition is broken... i am told but havent tried it that you can put your key next to a re-charargeable toothbrush stand and the battery will be recharged....
This happened in my 320cd and the charger in the ignition had to be changed
the keys charge in the ignition but sometimes when totally dead they require re initialisation. I had to do this recently with my key after i left a battery depressed in my pocket.
there is a simple key press sequence to do this, but i cant find it right now :?