Seems like it’d be cheaper to throw away the batteries every time you use them and just keep buying new ones.
If the truck can’t charge the camper batteries it can’t charge it’s own batteries either.
If the camper batteries are connected via heavy cables directly to the truck batteries, they will charge as much as the truck batteries do. If they’re cabled directly together, the truck cannot separate the path of electricity.
And... if you only get 13.8V ever from the truck alternator, while it may not be technically ideal, it’ll work and the truck apparently works fine that way.
I’d just add another battery before spending all the extra $$ on the DC to DC converter.
Less money for more real world gain.
It’s a false statement to say that you must have 13.8V to replace ANY energy into the batteries.
