The 12v battery in my 2014 model S died or the circuit disconnected on me without warning at all. I was locked out of the car completely. Even after the towing company forced open the door the car could not start, completely dead with no warning at all. I had to pay $300 for the towing company to do the force open and get the car to the dealer. I think the design of the 12v circuit is problematic. A critical function of opening the car door and starting a car can not rely only on a single battery or a non-redundant wire! Tesla refused to respond to my comment on the design.