[TAKPAK]

I see by your post that you have a 2013 model Montana. They had the newer "smart" converters/chargers then, so that shouldn't be a problem. I would suspect a weak cell in the battery. Even a group 24 should last overnight. HOWEVER, that said, were any of the vent fans running? Was the hot water heater running? You already said the "fridge" was on. Yes, there are a lot of "phantom" draws, but still it should have run overnight.

The argument rages on about what batteries are best. Generally, if you are plugged in to shore power most all the time, then one GOOD 12 volt deep cycle will do. IF you occasionally dry camp for a weekend once in awhile, then I'd put two good 12 volt batteries in, for the extra amp hours. If you dry camp a LOT, or have solar systems, then I would go with the "golf cart" six volt batteries. The BIG difference is........the 12 volt batteries (depending on size) will have a bit more amp hours to draw from, assuming same number of batteries, i.e. two 12's (in parallel) or two 6's (in series). BUT, the six volt ones will stand up to REPEATED charge/discharge cycles a lot longer than the 12's would, due to their difference in construction. So, occasional dry camping.....one or two 12 volt batteries. Lots of dry camping, then six volt batteries will have a longer life span. And, if you have a generator, that changes things a bit too. Hope this helps...........