1) If you want to run any electrical device for any period of time from a non-mains source, you should do the necessary calculations on power/endurance, or get a techie oriented friend to do it - the life of car batteries - or even laptop batteries is surprisingly short, especially when under heavy drain.


2) If you want to cook/heat food/make coffee etc in a remote or camping site - you would be better off forgetting electrical devices unless you have a portable generator - and use some chemical form of stove/burner - gas or liquid if you can't get access to a campfire.