About subzero temperatures, I've not much experience with my phantom, because I only have it since summer, but I have long experience with computers so I have a couple tips that can be important here:
- first, about condensation, the problem is not when you are flying, is when you put it again inside home or inside the car: if the phantom is cold, and you put it inside a warm environment, condensation would appear. Don't use it then! Try to help it dry faster near (not too close) to a heater, in a dry room (avoid kitchen, bathroom, etc).
- second, about lithium batteries and freezing temperatures: while cold doesn't break lithium batteries permanently, they last less time, and can stop working at all if they freeze, so don't let them outside if you are not using them. Fortunately, they will recover their capacity when they unfreeze (while a hot environment would damage them permanently). If you are in the field and have several batteries, keep the spare ones inside the house, the car, or close to your body while they are not used. Don't let them in a backpack over the snow because they could freeze. Fortunately, while in use, the batteries tend to warm up, so that will help them, but if they are exposed to very cold temps, the cold wind from the propellers could freeze them while flying and suddenly stop! So keep an eye on that! And of course, don't charge them when they are frozen or cold! They can have both problems at the same time: they will store less energy, and can have condensation, and nobody wants liquid on their batteries! Wait until they are at room temperature!