I have a fairly new battery but the cold just kills it. I left it outside last night as an experiment.. It was on a charger all night the night before and then sat all day and night and it's dead right now. It's a big worry laying in the tent at night and wondering if it will start. I have taken the battery out and stuffed it in the bottom of my sleeping bag for the night and had success, but that is a pain in the ass.
I'm blaming some of this on the cheap Bikemaster battery I installed. I just don't think it's as powerful as the Yuasa I replaced. I'm going to install a stock Yuasa and try an 8 cell as a backup and see what happens.