Battery insulation idea and prototype

[bujaman]

After reading how a few people made cold weather battery insulators, I wanted to give it a try. My to have a flexible version that can easily be put on or removed/stored.

From other form members these were the ideas I really liked:

1. The guy who went to Antarctica made his out of thin construction grade materials.

2. Another member made it out of industrial felt and sewed pockets for toe warmers. This seems to have the flexibility I was looking for.

If really wanted to forego the additional heatsource. I decided to pattern after an oven mit.

There are two fabrics used one is a 3m thinsulate and the other is a dual sided with one side reflecting 95% of radiant heat (or so the claim)

The thinsulate has an r score of 2.2. I went 2 pieces thick. I placed the reflective material facing toward the inspire on both pieces. Aside from less than professional sewing, does anyone have any concerns with this build before I test? Please let me know if you can think of anything I should be watching for.

My concerns:

Won't seal well enough and will have too much heat escape.

Seals really well and overheats.

Reflective materials will cause signal interface.

The prototype weighs 18g. If the test works, I can share the cut sizes i used. Let me know if you want to know where I bought fabric in the US, but I had to buy a yard minimum which is way more than you need for one of these.

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[JGF21]

Don't know that you'd need the heat-reflecting side. Once the bird started draining the battery, seems to me that would create enough heat to keep it warm, if properly insulated from the outside temps (which your thinsulate does). I have yet to operate in extreme cold, but was under the impression that the important part was keeping the batteries warm en route to your flight location, which a cooler with some handwarmers should take care of.

 

[Jason Boucher]

Don't know that you'd need the heat-reflecting side. Once the bird started draining the battery, seems to me that would create enough heat to keep it warm, if properly insulated from the outside temps (which your thinsulate does). I have yet to operate in extreme cold, but was under the impression that the important part was keeping the batteries warm en route to your flight location, which a cooler with some handwarmers should take care of.

I've flown in -15 degree weather and can assure you that the reflective surface will def help. I've seen times while flying quickly the wind would cool the battery down enough to get a cold battery warning. In warmer locations it may not be needed, but around here.. Keeping the batteries warn during the flight is also very important!!

 

[Maverik]

Here is a thought.. How about making the attached fabric into a pocket and then slip in a couple of reusable hand warmers..
Hot-Hands makes a single use one that is very light, or the Hot Spot or Hot Snapz Reusable warmers. That should make the battery feel quite toasty..

 

[bujaman]

Thanks everyone for the replies!

@JGF21 I could be wrong, but I thought the members using toe warmers were using them in flight. In case isn't a bad Idea to keep the whole case at temperature. I just drive far enough that my case looses that much temp from my house temp. I can see the merit for trips though. I do have the DJI battery warmer and I am okay with a 3-5% battery consumption for heating the battery that way. If I can get a full length flight in the next battery should be ready by the time I set down.

@Jason Boucher Thanks for the Feedback! I think it will help. Any worries about signal interference?

@Maverik This may not be possible, but my hope is to find a way to do it without the hand warmers. Its just one less thing to remember/forget. I realize that I may have a higher cost in materials, but I am hoping for a lower term cost because I am not buying hand or toe warmers for the batteries.

I am going to try and start testing this afternoon.

 

[droneseyeview]

Has anyone been able to do this with the Inspire 2?


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[bujaman]

@droneseyeview I have not tried with the Inspire 2. Although if someone from SLC has one and wants to give it a shot I have plenty of material to let them give it a shot.

I tested out the insulator yesterday. I think I need to do a little more testing. I took data at 5 minute intervals and at the low battery warning (set at 30%). I tested for two batteries one control and one test. I had about the same battery life with and with out the insulator on.

First off I flew with the following setup:

Inspire 1
x3
TB48

Outside Conditions
21 F
with 4mhp winds

Flight style was hover.

I have done a little analysis on it. If anyone wants to see the raw data let me know and I will try and upload a text file. I only had 2 batteries to test with so I will want to make a few more test trips to fill out the data a bit more.... Anyways here is my starting point:


I was a little shocked that I received about the same amount of battery life with and without the insulator (about 12 minutes with the x3 and TB48). I may jump back to the drawing board and give it another go at making my insulator. However, I did notice a significant drop in the variance between cells at each given interval and an increase in the overall temperature which are both positive. I am not sure how these two compare to other insulators.

 

[JGF21]

Reading other forums regarding ideal battery operating temps, it looks like you want to aim for a temp of at least 32 C at takeoff, with 38c being ideal. It took you almost 10 minutes to reach that temp. Lesson? Heat them up before takeoff. Then, let your insulator do its job keeping them warm.

Source: More performance from your LiPo (Tutorial)

 

[JGF21]

Also would recommend a test with actual flight as phase 2, as the cold air passing over the surface would cool the battery more, and more effectively test the insulator design.

 

[bujaman]

@JGF21 Thanks for the feedback. I will do moving flight next time rather than hover. That is interesting about the forum on temp as I thought the DJI battery warmer only heated a battery to 25 °C?

I will try and test again this weekend.

 

[JGF21]

Does seem rather warm if you ask me. DJI warmer shuts off at 30c, though, and it wouldn't be surprising if they were a little conservative.

 

[Eyeup Aerial Solutions]

I had a job just before Christmas over a cold day. Nothing extreme but I wanted to avoid any battery cooling problems as I wad flying over a fragile roof which would nit allow retrieval of a lost aircraft! I took the batteries in their usual ammo cases together with a couple if hot water bottles in a cool box. Thus works well and gets the batteries to a nice even temperature as the steel boxes spread the heat around. On the early (colder) flights I simply taped a small piece of bubble wrap around the battery compartment. Did it work? Well, the batteries were probably as warm after a gentle flight as they would get during our UK summer.

 

[bujaman]

I tried testing again to night. I removed the battery from the warmer as it shut off. By the time the ready to fly screen was up it was just under 24c. my air temperature was -4c. I didnt get to measure without the insulator this round because my tablet died.

Battery Temp reached 38.8c by 5 minutes which was an improvement. Battery life was still around 12-13 minutes at 30% warning. Although, I think this may also be a calibration issue with my batteries when fully charged I am only showing 4900 mAH on the TB48s and 3900 mAH on my TB47. I am going to try calibrating tonight.

I think I may take another go at creating the insulator too. Being careful this time to overlap the material past the battery housing. I think I have some gaps in my current make.

 

[arcticdronepilot]

I designed and use these to keep the Inspire 1 happy at sub-zero temperatures. They work by protecting the batteries from windchill and have space for handwarmers which provide extra warmth. cinetulz