All you'd really have to do is have the car's battery banks set up like an array of cartridges. If they all had an individual charge display, you could simply pull into a 'filling station' and swap out (by popping your hood and just pulling them out, like hot swappable hard drives) your run down batteries for fully charged ones, just like people do with propane tanks. Hell, the station could even charge you only for the difference between the energy in the battery(ies) you swap out and the fully charged one(s)...