The original extra battery wiring for my once-was-riviera had a
strange setup -the 120 went to a built in battery charger, which
powered all the 12v accesories, as well as charged up the extra
battery. No connection at all to the Vw system and the conversion; the
stock battery and 2nd battery never so much as waved at each other.

This van isn't set up for double batteries except for the above
system, which I still have, but I would like to be able to charge the
second battery while driving, and run all the kitchen stuff from it as
well.

I imagine I can just run all the Dc power to the kitchen from the
second battery, but how about charging it? I know some vendors sell
"kits" but this kind of thing is usually $10 bucks worth of generic
FLAPS parts.

I would like to understand; why can't you just parallel the batteries;
why do you need relays and stuff? Is there a schematic kicking around
somewere?

Nathaniel