Originally Posted by ruzam
Many years of personal experience with using LiPos in cold wx. It's all about the internal resistance of the cells, which determines how well they hold voltage under load, and therefore how much power you get. High-quality, high-performance lipos have lower internal resistance at normal temps. That's why they you get more power, with less battery heat. As the internal cell temp drops, their internal resistance increases at a much lower rate than the low-quality cells. Therefore, they maintain voltage much better under load in cold wx.
Check the PZ Sukhoi XP & other 1s UM threads. You will find plenty of info regarding flying UM aircraft with exposed batteries in the winter. Many of us have been flying these UMs & testing UM batteries for a number of years already, so there is no need to reinvent the wheel.
For a number of years, Hyperion 160s were far superior to any other UM cells in the cold. Of course, they were also by far the best performers in normal temps. Many of us have flown in -15 F wx with them, and flight-times to the 80% discharge point are far better than the cheapies. The older Turnigy Nanos were useless in the cold, but then they had very poor performance in normal temps as well. The newer Turnigy 160 mAh 30c cells seem to perform similarly to the Hyp 160s in normal temps, so they may also fare much better in the cold than the old Nanos. The MA cells also perform similarly to the Hyps, so they may also be good choices for winter ops.
A number of us also made little LiPo blankets to keep the cells from cooling off so quickly in the air.