Couple things to consider:
I once saw a proposal where EV's would be designed such that the battery packs will be swapped out at a "battery station" — similar to where you swap out a propane tank for your BBQ. Process world take less than it takes to fill up with gas if designed right.
Idea sounds interesting except for one thing: I don't think the idea will fly as I don't know about you guys but if I'm driving my brand spanking new EV with brand new batteries, not sure how thrilled I would be to swap them out for who knows how old replacements.
Also, if the batteries now cost, say $8K to replace, and have a life of 125K miles (two big assumptions), then you need to figure in an additional 6.4 cents per mile cost for each fill up. For 320 miles that comes out to $20.48 per charge. So in effect a "fill up" would effectively cost $22 + $20.48.
Also, it seems to me that the 320 mile range assumes some minimal cabin heater use (would need to be electric and energy used would come right out of the batteries, whereas with gas engine just uses waste heat from the combustion process) or some minimal air conditioner use (again would be electric and not powered by engine and energy for it would come from the batteries.)
Finally, I've also seen proposals where a charging line would be placed in the roadway, say in the interstate highways, such that even if it didn't keep that batteries completely charged , at the minimum would greatly increase range.