With my boiler playing up over the last week and a few freezing nights whilst parts have been on order, I’m reminded of two things. How annoying it is to be cold, and how quickly the body adapts and forgets that your house is about as warm as your fridge. Batteries on the other hand, do not forget, and as we know are very temperature sensitive. This is where I could insert a pun about my wife, but as the boiler is now working and we are speaking again I’ll resist the urge.
How do you get good performance from LiPo batteries when filming in the cold?
1. Warm Them Up
The simplest thing of all is to keep them warm – however this is easier said than done. If you are flying an Inspire, DJI have come up with this clever battery warmer thing (below), which uses a small amount of the battery’s charge to heat the battery pack up. Designed to be used for ten minutes immediately before flight, this self-contained unit is a pretty neat idea. The problem is that it’s doesn’t appear to be insulating (simply a heating element), so the little heat it generates will dissipate quickly. On the plus size the whole thing will fit in a coat pocket, so you can get your next battery ready prior to each flight.
DJI Inspire Battery Warmer Thing (about £15)
For everyone else, there’s Hand Warmers. Stick these in your pocket next to a lipo and it will soon start to warm it up. Better still get a few of these and an ice box or themal freezer bag and you’ve got a warm environment to store all the batteries you need for the shoot. Just remember that they crystals take a good ten to fifteen minutes to start putting out good heat, so make sure your battery packs are warmed in advance. Keeping them in the boot of the car won’t work beyond the first hour, particularly if it’s a very cold day. At a push keep them in the front foot-wells with the engine on and heaters pointed at them.
With any heating device make sure you are not putting out too much heat so that you don’t damage the batteries.
Hand Warmers (about a quid a pop)
2. Land Early
No matter how well you warm your packs prior to take-off, you are going to find they lose heat quickly, particularly once airborne with cold-air flowing over them at however many knots you are flying in. You cannot expect to get the same performance out of LiPo’s in the cold. In my experience they do some funny things too. In Iceland at -10°C I had an Inspire battery go from 30% to 0% in an instant. Fortunately I was a few feet from the ground coming in to land when this happened. Oh and this was despite the OSD telling me the battery was 32°C. Don’t believe the instruments if your gut is telling you to land.
Or this could happen:
I’m speculating here, but but it looks to me like the blades have stopped before it hits the deck. I’m going to guess battery voltages fell below the min for the ESC’s which were shut off. If anyone knows differently please let me know and I’ll update this.
3. Don’t Charge LiPos In The Cold
It can reduce the life of the batteries. With the DJI warmer, I find using it before charging helped in cold environments, but ideally charge everything at room temperature. At a pinch if you are using a generator make use of the exhaust heat (again making sure you don’t fry the batteries or start a fire).
4. Don’t Forget To Keep The Pilot Warm Too
Finally, wrap up warm and wear some thick gloves. The cold slows reactions, impairs decision making and is highly distracting. A warm pilot is a safe pilot.