Years ago I used coolers.. Bought ice from the park.. Then the park gave us the bad word.. It was going to cost us to plug in..Yup, I think it was 4.00 more a night to plug in... So I bought a small (Dorm/office size) Fridge and instead of buying ice.. I made it (just enough for drinks) Used that Fridge for several years.. In fact I used it right up to the day I brought the Class A home.. Sold it to another camper who uses it still far as I know.
With the door tied shut (I used a "Tie down" strap) the thing will remain cool 8 hours and is very hard to open.. I set it on planks next to my trailer in country where it waS safe to do that.. in Bear country I'd have locked it up inside but I figured if I was going to pay to use electricity. I was NOT going to pay for ICE.. That thing saved it's purchase price several times over.