Our 5 series frightened me yesterday big warning messages on the i drive 'excessive battery discharge' and all I thought I had done is opened the door. I had been sat in the car having lunch so the car had 'gone to sleep' and opening the door 'wakes it up'. Couldn't get the error to go away so after internet research could be battery dying or the battery condition monitoring system or some other expensive trip to Dealers. One post mentioned after-market items such as tow bars or I pod connectors so I thought could it be the usb charger for my phone so I unplugged it this morning and lo and behold no more error messages. Just after that the flat tyre monitor went off so got to fix the slow puncture now. Still the zed keeps going.