Yep, 10-4 thanks 

Chrome - I knew what you were talking about when you asked the original question. Even a car battery wouldn’t last that long due to the amp draw that electric heaters have. Even when used in a car, the battery is constantly being recharged by the alternator. About the only way that electric heat would be a viable heat source would be if it was connected to a generator.

They do make a number of small car heaters intended for defrosting car windows things like that that plug into a cigarette lighter. I understand that carrying out a big car battery so I get that, not that stupid.

If you're looking not to buy 1lb cans all the time, get yourself a Flame King refill kit.

12 car batteries = one 16.04 oz can of propane

Chrome- Seeing that electric heaters are direct resistance. I don’t think that you would want to carry a battery large enough for that to be a viable option.