The freezing cold is really bad for batteries. I had a couple of brand new AGM batteries that I stored outside all last year (inside my trailer) and they both went bad. This year I have taken the one battery from my new trailer and stored it inside. I think also if you store it in your basement you should elevate it off the concrete floor. And keep it on trickle charge/maintainer if possible - I havent yet started doing this as it was fully charged when I brought it inside.