Was this colder than the day you saw it say 45 miles? I've been riding on 25-30 degree mornings and I can see a drastic shift in my battery level when I'm out too long , or when its windy. As long as I keep the battery indoors at home and at work I don't see the problem. One night I experimented and left the battery on the bike overnight in my unheated garage. (25 degree low)When climbing the biggest hill on the way to work the next morning, the battery indicator went to zero. When I got to work and warmed up the battery without charging it, by bringing it indoors, the battery said full charge all the way home that same day. Since then I always keep it warm and I haven't seen it do that again. It helps that the plastic casing around the battery is black, on warm afternoons I put it back on the bike in the sun.