you actually want to charge the lipo's at room temp, or 70 to 80F. Charging at 40F or refrigerator temps will damage the pack =)

A fan is great for cooling off a lipo, but be careful because it will cool off the outside faster than the inside, and you want to make sure the very most inside part of the pack is about 80F before you start charging. you can get away with up to 90F or so, but it's getting more risky. Usually w/o a fan it takes 10 to 15 min. With one, it might cut that time in half if you use room temp air and there aren't deep internal parts in the pack that would keep the heat in when the surface is cool.