I assume you mean you ruined the phone batteries, not the car battery. In that case the most likely culprit would be the cheap cigarette lighter adapter you got for 3 bucks at the quickie-mart. If you're using a decent charger/adapter you shouldn't have that issue. 

well..  it is a BMW ( MINI) what did you expect? bc

I'm not sure how a phone charger can ruin the battery... Even if you left them connected, the cigarette lighter should become unpowered when you shut off the car....

As for the sensors - what sensors?

This can be an electrical issue, or perhaps the computer software has been corrupted (not unheard of). If this is the case, a reflash of the software by the dealer 'may' correct this...

I bought a 2007 Mini Cooper Base used.  I have all sorts of weird problems.  I have plugged into the cigarette lighter to charge my phone  and ruined 2 batteries.  (Won't do that again.)

Also, sensors come on, go off, come back, then go off again forever.

Would that be an electrical problem?  And does anyone know how I might diagnose/fix it?