If it was tested underload with a clamp on tester then the battery is good. You say that you have a BIG Boy and a B.I.R.D that controls the Bog Boy. When on the genny or shore power the BIRD charging system first charges the house batteries and then when they reach 13.2 volts the Big Boy solenoid is activated so that the system now charges the chassis batteries. If you house batteries are not getting up to 13.2 volts then the chassis batteries will not get charged except by the alternator.
Now you have to ask what is running the chassis batteries down that fast overnight. Either something is left on, or the chassis batteries are only maintaining a surface charge but that is normally detected when you test the batteries underload. The first thing I would do is to buy a battery terminal wire brush and remove the battery cables and clean the posts and the inside of the cables until they are bright silver in color and I would also check the water level in the batteries. Most of the chassis batteries are low or no maintence batteries but you can still pop the tops and check most of them. Once full of distilled water and clean terminals then try it again. If they still run down then I would have somebody check the batteries under load again.
Your RV30 will charge both the house and chassis batteries at the same time. There is a fuse on the RV30 for the house batteries and one in the chassis battery box for the chassis batteries. Also look around the battery compartment and make sure nobody has left a cable off of either the house or chassis batteries. It is easy to have one fall down when working on the batteries and miss connecting it back up. Let us know what you find out and we can go from there.
"Gunner" USN Retired, Airdale
2004 Monaco Signature 44' Conquest. Detroit 60