So I was reading about Tesla's plan for battery swapping. I didn't think that was such a great idea, since you would be leaving behind something that was a good fraction of the cost of the car. Might there be a better way?: So, it's the future: You've been driving around town, and used up half your cheap car's 90 mile range. (Not a Tesla, obviously.) Suddenly there is a big crisis-or-opportunity, and you need to jump on the highway and get somewhere 200 miles away as fast as possible! There is no need to go home first, (which is the wrong way anyway.) So what can you do? Answer: You drive to the nearest rental place and have them latch a gas trailer to the back of your car. This device would be a gas generator plus tank, and would charge your battery while you are driving. (I assume, it would need to generate power faster than your car can consume it at highway speeds.) It effectively turns your car into a hybrid. But the advantage is that the car would cost less, and you wouldn't need to carry the weight of the engine and tank around except on the days you'd need them. (Maybe 3 days a year for most people?) So my question is: How big would such a generator need to be? Could it attach to a hitch like a carrier rack? Or would it need it's own wheels like a trailer? (I'm assuming that the latter would make the car more difficult to drive.) I suppose the government would have to mandate a standard plug for power and brake lights. How difficult would that be?