I have the battery warmer linked to above and it works great. I used it today to keep 2 of my Phantom 3 Standard batteries warm on a hike along a river in -10C temps. Had no problems at all. I plan on using it when I get a Spark at Christmas.Cold weather will definitely shorten your flight time. Keep them warm prior to use. I keep them in my pocket so they don't get cool. You can also buy battery warmers. Cold = Bad
https://www.amazon.com/Turnigy-Programmable-Lipo-Battery-Warmer/
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I have the battery warmer linked to above and it works great.
Yes, I power it with one of my batteries that I use for my Syma X8G drone. It takes 3 cell lipos. I just had to buy an adapter to connect it to the lipo banana plug. Right now just use a cd pocket stuck to the outside to hold the Syma battery but will be buying an extension so I can put it in the bag to keep it warm also.