The nerd in me is getting curious about how the traction battery, 12V battery and vampire load are interrelated. Assumptions based on other posts There is a 12V battery that powers the car when the traction battery is not engaged (when your butt is not on the driver's seat). This battery is a "normal" lead acid type. The traction battery looses x miles per day above simple self discharge in what has been described as Vampire Load. The 12V battery is charged from the traction battery at 15V when the traction battery is engaged (car on). Questions 15 volts seems mighty high to be charging a lead acid battery. Is the 12 volt battery a (sealed) lead acid type? A vampire load on the traction battery while parked would indicate that the traction battery is being engaged for a period of time on a regular basis to replenish the 12 volt battery system. Has anyone verified this? What is the current draw profile on the 12 volt battery? It would be interesting to log this with a current probe to see what the static draw is, how often the traction battery is engaged to replenish the 12 volt battery and exactly what charge rate is used to replenish the 12 volt battery. I am sure there are lots more questions to be asked but I figured this would be a good place to start.