I have
I have done the exact same thing but only with a 30 amp plug. I made my own adapter for my old trailer, I just purchased an adapter at wally world for less than the one I made from HD depot parts. I gave my old one away with my trailer when I sold it. I would not exceed 15 amps draw so no air micro wave or any combinations that have a heavy draw beside you circuit breaker should trip but who knows. So common sense needs to prevail but I see no problem charging your battery and cooling down the fridge. Well that's my 2 cents worth
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