So my Model S P100D is giving me an error message "12V Battery Needs Service - Replace 12V Battery Soon". Its winter here in the mid-Atlantic, but the car sits in a garage and is plugged into a wall charger when its not being driven. I called the local Tesla sales/service and scheduled a replacement. They called the morning of the replacement and cancelled the appointment, because they did not have any 12V batteries for a Model S. I am really worried about Tesla, this is poor service and its poor design. I have other vehicles that can sit for months without being plugged in and start right up from their 12V. I have farm equipment that can stay on a trickle charge all winter and start right up. You would think a company that prides itself in electric vehicles and power management would be able to do better than this for a vehicle that has been plugged in and is less than a year old.