I think if it was related to charge, the device would stop charging but keep playing, but maybe the iPhone detects the drop in charge and treats like a disconnection.
If it is down to charge, charging from the 12V will solve this problem. There are some other threads about the charge from the USB socket in BMWs not being enough to charge iPhones and iPods.
I've not had any problems charging a 5th gen iPod nano and an iPhone 4 from the USB. Charging the iPhone 4 from the cradle always works too
F25 xDrive20d SE __ professional multimedia package | dynamic package | climate package | 309s | xline | xenons | electric seats | folding mirrors | business speakers