Winter Flights Need Warm LiPo Batteries

The winter chill will arrive if it hasn't already. Time to look at your power sources and how you can help squeeze more flight time in frigid temperatures. LiPo battery packs lose about 20-40% of their capacity and performance potential in cold weather. Voltage levels fluctuate when the internal battery temperatures slow the release of the battery's stored charge. They can start fully-charged but appear to empty very quickly because the demand is greater than the supply is releasing. This can cause flight systems to have inaccurate reactions to power measurements. Systems will report low battery power remaining or trigger shutdown early. Warming batteries before flights can significantly improve cold weather performance.

The Bebop packs are enclosed inside a thin-walled black plastic shell that does provide a little protection from the elements. However, if a battery is charged and rested in a home before a flight outfoors its internal temp could be rather low for to perform as expected. LiPo packs have a starting-temperature sweetspot of about 95F to maintain winter flight as expected. That is a good start to have enough heat built-up to sustain normal performance throughout a cold flight.

I use this $15 'Turnigy LiPo Battery Warmer Bag' I bought from Hobbyking.com last year. It is Adjustable and monitors its own temperatures! There's room to warm two Bebop 2 battery packs. Making a DIY warmer isnt rocket science. But, this battery warmer is the best commercial-off-the-shelf thing I have used yet. Such hi-tech warming methods in the past..like, pockets, a baby bottle warmer, and chem-pack hand-warmers. Last winter, a user covered the Bebop battery with a patch of fur. It was stylish and may have even kept it warmer to some degree.

Regulating specific temperatures should not be left to the warmer controls. It is thermo-regulated..but I would acquire a second opinion and limit potential over-heating problems.

So, warming is good...but too warm is not good. Damages occur inside LiPo cells when internal temperatures approach 140F. Bebop packs do not seem to run hot normally (even in Texas summer heat). But, heat and heating can become a problem if a pack is warmed too hot and then ran hotter during a flight..+140F can happen. Measuring pack temps after flights and monitoring the temps in the warmer bag can give you a better idea how much heating can be applied safely. 

Here is the warmer powered by a LiPo pack and an adjustable low-voltage alarm to monitor the battery's charge level. This alarm will let you know when the battery reaches its lowest safe capacity before over-discharge and damage. But this alarm will not prevent over-discharge all by itself. The user needs to remove the LiPo when the alarm reports the low-voltage condition. Allowing it to continue to discharge below 9.6 volts will cause cell damage within the LiPo pack. It is a good idea to stay nearby when using this configuration.

Here is an $15 12v Sealed Lead-Acid Battery powering the warmer. That is the cable included with the warmer. This is a similar battery to what is in automobiles..and commonly used in RC base stations and support equipment. Here is an adapter to use a car cigarette-lighter.

These batteries can supply power for along time. However, it is a good idea to also use a 12v low-voltage alarm..or even with an automatic cut-off function. Like the 12v Battery Low-Voltage Alarm & Over-Discharge Protection Board. Just program it to cut-off at 10.4volts. $11 of Yes, Please! It is connected between the battery and the warmer or any other 12v load.

Maintaining battery conditions can help flight enjoyment and reduce risk of losses..why not warm'em if you got'em before you fly'em...or, Winter may take a chilly bite..leaving a chunk missing in your drone-soaked soul...

Have Fun!