I agree with ardvark. It comes down to a question of haw many AMPS do the jacks draw, vs how many amps the converter can supply. For high current loads, the converter may not supply enough current and they really need to draw power from a fully charged battery to work properly.
I don't like to make plans. They cause the word "PREMEDITATED" to get used in court!
DON'T FEED THE VULTURES!
My Body is a Temple! Ancient, Crumbling, Probably Cursed . . .