My 2000 350ES Fourtrax is stored in an outside shed which is connected to the main barn at a pubic horse boarding barn. We've had extremely cold weather lately and it would not start. We pushed it into the main barn and left it overnight, it started right up. Battery is new. What can I do to get it to start while being stored outside? It cannot stay inside the main barn and I do not want to leave anything like a battery tender plugged into it for any length of time. I can hook up something for maybe 20-30 minutes before I start it, not sure if that would help.