Re: Strange battery issue
Reply #2 –
I can't say this is your problem, but those terminals on the starting battery need to go. They probably aren't conducting too well.
Quality profession cables with permanent terminals will save you so much grief. Not the cheap stuff consumer grade stuff, the heavy duty ones from NAPA or similar.
Personally if they are otherwise in good shape, I would probably pull both cables and solder on lug terminals and heat shrink them, then install military or ordinance style terminals on the battery and bolt the cables to them. Since you are using conventional flooded batteries, some anti-corrosion spray would also be in order, and maybe anti-corrosion washers on the posts.
You might want to double check those are the correct batteries for that application. They seem awfully small for the battery box.
I don't like the wing nuts on the coach battery. They really should be switched to military or ordinance style terminals on the posts. The wing nuts will loosen and they provide very little contact area.