I have a "plan" (we'll see where it goes when I get to it) to do something like this on my Jeep for camping. Except, instead of an external battery, my plan is

I have a "plan" (we'll see where it goes when I get to it) to do something like this on my Jeep for camping. Except, instead of an external battery, my plan is to get either an Optima or Odyssey hybrid battery (maybe two, if I can fit them under the hood), that can be used for cranking and deep-cycling.