The small panel is for the chassis battery for parasitic loads that will discharge the chassis battery.
One item over looked for chassis battery discharge is the LP detector that on older coach's had a switch in the display area to cut off the 12 volts for LP.
Bay Star owners have been having battery discharge problems with the house batteries so not sure where your LP is feeding from.
There have been threads, Bay Star Section, in
QT's # 3 with some Mods that might help with the battery problems also
this link describing the Solar panel wiring at end of the link. Wiring for panel was wired into the heavy battery wiring box on my firewall.
If you have the ability to keep your coach plugged into a 120 outlet all the time your battery charging system a
BIRD OR B.I.M. System will keep all your batteries fully charged.
All the links below in my signature are for your Newmar.
Enjoy the forum and safe travels.