Sunseeker House Batteries not charging

My friend has a 2012 Forest River Sunseeker Model 2860DS that doesn't seem to be charging the two 12v house batteries when plugged into shore power.

There is a large rotary switch next to the battery compartment that has: "Blue Sea System Single Circuit 6006" printed on it and it has an "ON" and "OFF" position. I assume this is the disconnect switch.

When I switch it to "ON" the batteries are being charged with about 14v, or so, but will NOT go into a float charge when the batteries are brought back up to full charge. It just keeps charging away to the point to where the electrolyte starts boiling.

When I first checked this, after my friend noticed that water was dripping on the ground below the batteries, I check and found all battery cells were full to the absolute top of both batteries. I removed a bunch of electrolyte out (abut 48 ozs) so that the level is down about half way to the cells.

Does this unit have a 3-stage converter/charger on it....or just a single that is manually operated? Never heard of such a thing.

Any and all info will be greatly appreciated.

thanks

Ron