UPDATE-
Went back to the trailer last night for bed with a frost warning overnight (COLD) and battery still showing 75%.
Turned the furnace on and instantly went to 65% then 30 seconds later to R and the gas sensor red light turned on meaning low battery.
Decided to sleep at the inlaws cottage just in case since we have a 19 month old. Wife just went back to the trailer this morning and says its back to 75%.
I'm really confused