What is the best way to keep batteries charged during the winter while in storage with no electric, I don't want to bring them home. Addendum: It is a FW with no Generator.
Make sure they're charged and then disconnect the battery cables. Mine last just fine that way in my DP.
The three batteries in my rig pictured below get used during Sept moose hunting, the battery disconnect flipped (which unlike most MHs, kills everything) and then it sits for 11 month until next hunting season. The batteries lasted 9 years. I changed them two years ago.