Originally Posted by 33 RLDS
Minimally it should be un-plugged as the CO2 and Propane detector will suck it down quick. Ideally you want to take it with you and leave it on a trickle / maintainer charger like a battery tender or such. If it was discharged and froze its probably shot. If not, it should come back up again when plugged in to shore power..
^^^ This. I remove my battery at the end of a camping event, and take it home with me and connect it to a trickle/maintainer charger. They are cheap (around 30 bucks or less).
I have three of these chargers; one for the camper battery, and the other two maintain the batteries in the jet skis. I used to replace the jet ski batteries once a year it seemed. With a trickle charger, they go well over three years of good service.