12V circuit only works on shore power or generator

So I took the advice to have the battery checked out. Battery is good. Talked to a couple vendors about my current system produced by B-M Manufacturing. They led me to Parallax Power who makes a replacement for the bottom end of the 6345. They say the problem is in the bottom of the unit which handles the charging and converting. So for $220 bucks, I'll give it a shot.

I'll report back when I get it installed.