Not sure that storing a battery inside the trailer is a great idea. If it is left that way long enough to discharge, it could freeze and crack, letting acid out. Also fumes given off, even while not charging, can accumulate over time, and a spark from anywhere, even static discharge, might cause an explosion. I would not want to take the risk.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.