I've also encountered the idea of swapping batteries at the fill station. This idea has a lot of problems too but probably gives the best end user experience.

I've also encountered the idea of swapping batteries at the fill station. This idea has a lot of problems too but probably gives the best end user experience. You're probably thinking of a startup called http://www.betterplace.com http://www.betterplace.com . I wonder what their analysis on gas prices would be to come to the continental US (their strategy right now is to go for densely populated areas).