I have been charging my AC70 through the supplied 12v car adapter but have recently come into some issues with heat and melting of the thin wires in my camper as well as a blown fuse when trying to charge it in my truck cab. I do not have an inverter in my camper so charging off AC power on the road is not an option, instead I would like to try and wire an output off my house battery terminals so i can pull DC power directly from those while in transit (I have a dc-dc charger connecting my alternator so the camper batteries charge when its on).
I attempted to do this already and was having reverse polarity issues. I wired heavy 10awg cable directly to my camper battery bank with mc4 connectors on the other end (so I could connect the bluetti supplied solar input charging cord that plugs into the xt60 dc input on the AC70), purchased a separate mc4 in line positive fuse, all good up to this point, multimeter reading 13.79v. I then connected the mc4 to xt60 cable and checked the polarity at the male end (the one that fits into the bluetti) and the polarity was negative 13.79.
I am not sure if this is an issue with how I wired it or how mc4 connectors work in general? I am thinking maybe someone has a better more practical solution so that I can actual charge this unit while on the road.