Have you seen www.betterplace.com? Their basic idea is to have a standard set of batteries which can be topped up at charging stations at home, work, and elsewhere. For longer trips, there are automated battery switching stations. From the how it works section:
"For trips longer than 100 miles (161 km), battery switching stations will be available roadside. Stations are completely automated, and the driver’s subscription takes care of everything. The driver pulls in, and the depleted battery is quickly replaced with a fresh one, without anyone having to leave the vehicle. The process takes less time than it does to fill a tank of liquid fuel. "
"For trips longer than 100 miles (161 km), battery switching stations will be available roadside. Stations are completely automated, and the driver’s subscription takes care of everything. The driver pulls in, and the depleted battery is quickly replaced with a fresh one, without anyone having to leave the vehicle. The process takes less time than it does to fill a tank of liquid fuel. "