One 100 watt solar panel and a small controller will assure you never have another dead battery IF the unit is stored where it can get sun light. I got tired of watching my batteries go way down in two weeks. I started pulling fuses of the parasitic circuits when I would leave it.
Then I installed disconnect switches to both batteries. That worked, but was a pain remembering to cut them off each time.
Installed one 100 watt solar panel, 20 amp MPPT controller and then started just leaving all switches on and fuses in place. Batteries are now always at or above 12.8 vdc.
This was a $250 fix that I should have done when I first bought the Aviator, but hey, live and learn.
I know NOTHING about cold weather effects on batts as I avoid cold weather like the plague!
2013 Silverado 2500 HD Duramax/Allison Tuned
Aviator Wright Flyer #1919
"First In, Last Out". 11B4Y
DAV, MOPH, VFW, 5/7 Cav,1/8 Cav Assoc.
11th ABN Pathfinder Co. N7MIP