I learned the other day that the decline in battery power in cold weather is not linear, it seems exponential. I discovered this when flying low under the overhang of a grove of trees on a very cold day my battery quickly declined. The P2V first tried to land on its own without going up. It was only about 30 feet away from me so I thought I could fly it back. The alternative was to land it in deep, powdery snow and I didn't want to fill it up with snow. While trying to fly back it switched to RTH mode, and wanting to be at 60 feet altitude, shot up into the trees. No damage other than 3 broken props. BTW, when it decides to come home it goes up in a hurry. What's interesting is how quickly the battery went away. I had started the flight with a warm battery, having had it in the house. I think the propwash in cold weather really cools the battery down in a hurry. The lesson learned is that in really cold weather when the battery is at 50 percent you want to be pretty close to home, because the other 50 percent is not going to last for long. It's not linear.