Batteries don't mind the cold of a garage (though they can be effected in flying in very cold weather). They'll self-discharge about 2% per day if you just leave them set. I leave mine in the cellar on a wall-wart plugged into an appliance timer to jab them for 30 minutes (NiCads) or 45 minutes (NiHM) every day. That way they're always topped off. A couple of us in the local club(s) fly year-round. Skis turn the winter world into one big airstrip. Frozen lakes are perfect fields, too.

Last year we had bare & taxiiable ground every month of the year. Global warming I guess. Best part is: no bugs.