Not a direct answer to your question.
A close friend owns an older Jeep. He parks it outside and does not drive it that much. He keeps a solar panel on the windshield/dashboard that plugs into the power point (used to be called the cigar lighter). I ask him if it works and his response was "the battery does not go dead anymore". I also ask him where he got it.... harbor freight.
Never been to a camping world. I prefer Dick's to be honest.