Keeping batteries warm

Discussion in 'Cinestar Misc' started by Nick Wolcott, Dec 2, 2012.

  1. Nick Wolcott

    Nick Wolcott Member

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    I know to keep batteries warm before flight, but has anybody tried insulating batteries for inflight warmth? I know they generate their own heat but I still get shorter flight times in the cold even if I kept the batteries warm beforehand.
     
  2. Jason Smoker

    Jason Smoker Active Member

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    i have seen pics of hexas with like cooler box deals on AV200 360 gimbals but never tried myself
     
  3. Arthur Vieira

    Arthur Vieira Flight Squad

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    I had the same question posted under the MK Forum in the middle of this year. Sorry I don't have the link right now as I'm on a trip and my internet is very bad.
    The answers I got were very interesting, most people keep them warm before flight and then rely on their self generated heat during operation but some people use those pipe insulators tubes and install the Lipos inside them on the multirotor, just like a "burrito".
     
  4. SteveWilson

    SteveWilson Member

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    I'm not sure I would blame the batteries for shorter flights if they are warm when you start flying. As we know they do generate enough heat to keep themselves warm. I'd be inclined to look at what other influences the cold weather has on the flight efficiency. We need to design a test to control for battery temps I guess. I like Arthur's burrito idea.
     
  5. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    I did some Google searches but have not found anything that would appear to be the link to which Arthur refers. However, based on some web pages I did see, and because, in the USA we have lots of government warning placards, especially on aircraft, I must ask you guys to print out the following text and affix it to your burritos:

    Remove LiPo battery before consuming burrito.

    Seriously, though. Options might be:
    1. Use a layer of thin bubble-wrap or packing foam (about 3mm thick).
    2. I wonder if there's a small enough LiPo/Nomex bag we could use.
    3. Use a pack of chemical hand-warmer (Google "hot hands").

    Certainly place the batteries in a small insulated cooler before you head out on location, put the used batteries back in it and they'll keep the ambient temperature in the "cooler" warm

    Andy.
     
  6. Howard Dapp

    Howard Dapp Active Member

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    Cold air is heavier and more dense that warm air, that along with poor lipo performance in the chill. Could be both factors combined.
     
  7. Nick Wolcott

    Nick Wolcott Member

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    I'll experiment, see if a hand warmer strapped to the burrito makes for longer flight times. As an airplane pilot the cold dense air meant better performance, a lot of that was due to better combustion but I also thought the denser air gave the prop more to bite into.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    That was my afterthought too. I wonder whether the issue is not so much the altered performance of the LiPo but the motors? The conventional wisdom seems to be: "How cold can neodymium magnets get? Generally, the colder they get, the stronger they are. We have yet to find the low temperature that hurts them. Temperatures as low as -40°C to -60°C don't pose a problem." See http://www.kjmagnetics.com/blog.asp?p=temperature-and-neodymium-magnets

    So could it be the bearings that get stiffer and demand more current?

    What else would change beyond air density?

    Andy.
     
  9. SteveWilson

    SteveWilson Member

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    Nick, how much shorter are your flights in cold weather with warm batteries? How cold are you talking? We haven't seen much of a drop in duration as long as our batteries are close to room temps, but I'll admit we haven't been very scientific about documenting our times. When we are testing different props, etc, we keep a very close watch, but after that we don't monitor nearly as close.

    I agree with everyone else, my gut says the props/motors should be more efficient in colder air.
     
  10. Nick Wolcott

    Nick Wolcott Member

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    Steve-

    I'm talking cold, like 10 degrees F and below. It's not that cold now and I'm hitting the road soon, so it might me be a few weeks before I get back to you with some accurate numbers.
     
  11. Shaun Stanton

    Shaun Stanton Active Member

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    I find that sticking the batteries in a soft thermal cooler actually insulates very well. I have flown for a few hours in 15 degree temps and the batteries seemed to stay nominal warm. I would put the used battery's back in the case and the heat from those would keep the pack warm.
     

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