Read a rather interesting blog on the techniques used by the Tesla software to tender the on board 12 volt battery. Briefly, there is some history of the onboard 12 volt (lead acid) battery on each Tesla (S and X) wearing out much quicker than in a modern ICE vehicle. The blog I read (sorry, no link) talked about how the onboard software was essentially never letting the 12 volt battery fully recover with a float charge. The blogger recommended a larger capacity 12 volt battery, have the software rewritten to allow the 12 volt battery to get a float charge as soon as being plugged into shore power (even to the detriment of recharging the main traction battery as fast as possible) and have the 12 volt battery kept at float charge off of the main traction battery when not plugged into shore power. Opinion: I really hope that the 12 volt battery system is less prone to maintenance in the Model 3 compared to the Models S and X. I also hope that its location is such that a swap out does not entail alot of trim disassembly . Thoughts?