I store all my stuff in my unheated shop, for years now. I just go out and put the batteries on charge once a week, cycle them once or twice during the winter. It hasn't affected my fuel, or any of my guns or ammunition. The thing I would think about would be some ventilation, to keep moisture from building up, that would affect the wood some, and if you have any unsealed fuel, could cause a moisture problem in it. My shop is a 24x20 frame with metal covering type structure. I also keep a lot of computer stuff out there, switches, routers, parts, printers and whatever.