Here is a PFD
of the battery systems in a Newmar coach.
Your chassis engine battery is at the mercy of your house batteries when plugged in and the battery cut off switch is on. The house batteries will be charged first than the engine battery and with coach under cover the small solar panel will not be able to make up for the parasite drains off the chassis battery, radio, ECM, TCM, LP Detector.
You will have either the Bird System or the B.M.I. System to charge your batteries.
With the power cut off and if batteries are wet cells and not topped off with water plus aging the batteries will begin to weaken in holding a charge.
The house batteries will need to be almost fully charged before the chassis battery begins to receive its charge.
Most years I have had my coach plugged in all winter, this winter I did not have plugged in until mid Feb when it was real cold.
Batteries were not charged since Nov to Feb period.
Placed batteries back on charge in Feb and steps would not move because of a dead chassis battery, tried in March still no steps but could start the coach engine using the battery boost button on the dash because the house batteries were now charged.
I have AGM's two 12v I installed in 09 when I removed the two 6v wet cells.
AGM's worked great when traveling back and forth to FL. dry camping at CB's overnight on trip.
The coach has been plugged in since Feb and all batteries including the chassis battery are now fully charged my chassis battery is the original chassis battery with the 03 coach.
I just picked up a MADP for someone and all batteries were dead while coach was at a campground in N.H. all winter.
Nothing worked used a car jumpers on chassis battery for a couple of hours and was able to get coach started and drive home.
Chassis battery was charged but house batteries needed work 8 of them cut them down to 4 and swapped one of the four with broken lug and redress all connections and battery cables and put a stand alone battery charger on batteries to bring charge up and now have that coach plugged into house working off it converter.
If your batteries and cables are good and clean plus ground cables to chassis frame are clean the batteries will recover pretty fast some times you may need a stand alone battery charger to help.