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Inflight Battery Warmer

Discussion in 'Inspire 1 Discussion' started by damoncooper, Jan 23, 2016.

  1. damoncooper

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    Necessity is the mother of invention

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  2. damoncooper

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    Wraparound version
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  3. damoncooper

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    Mad angler had noted

    "Someone posted this earlier today that caught my attention:

    "Looking at the configuration, the Inspire battery cells are located in such a way that 4 cells are along each side of there battery, [and] there is temperature monitoring as part of the smart circuit and its located with in the pack and looks to be buried in the center.

    Due to the open nature of the Inspire and looking at the cell configuration its possible the outermost cells could become susceptible to rapid heat loss in cold conditions and the temperature could drop massively compared to the centre cells causing voltage sag, its easy to see why DJI developed the insulation pads to keep the temperature up.

    Pre heating the pack in cold condition is an absolute must imo and some of the ideas posted around adding insulation around the back end of the craft are also worth looking at if you are flying in colder temps. "

    I agree.
     
    Phatzo and Mad_angler1 like this.
  4. damoncooper

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  5. damoncooper

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    Attached with strips of 3M Dual Lock. Toe warmers have their own adhesive. Good for 6+ hours and multiple batteries.

    Stay warm.
     
  6. KranMc

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    Any chance this would mess up the compass since the active ingredient in the warmers is iron and other chemical(s)?
     
  7. damoncooper

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    I'll find out!
     
  8. bluethundr

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    The temp sensor is NOT in the center like I thought as well. It is on outside of the packs of cells somewhat white caulked between the cells.. I thought this was for sure a funny/bad place for this. I only know this since I got a bad battery for free and had to swap out the white top of one of mine that had been chipped.
     
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  9. Mad_angler1

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    There may be some QC differences as the one I saw was in the centre but that's good info thanks

    Possibly they are just putting it in randomly in assembly.

    White gunk will be heat compound

    It's all about building up as much data as possible, nice work on the warmer I like
     
    #9 Mad_angler1, Jan 24, 2016
    Last edited: Jan 24, 2016
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  10. damoncooper

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    Used this today and it was AWESOME.

    Temp at takeoff was 24.5C and end of 30min flight was 38.5C. Green cells the whole flight except yellow at landing at 10% (normal). Outside temp was -7C.

    Right in the sweet spot for optimal discharge performance between 20C and 40C.

    Previous days flight without inflight battery heater had starting temp of 15.5C, dipped as low as 14C and ended at 19.5C.

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    #10 damoncooper, Jan 24, 2016
    Last edited: Jan 24, 2016
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  11. Rich Sugden MD

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    Not sure I understand ... all LiOn batteries, as far as I know, rapidly heat up when under load ... so, if you start off at a reasonable temp., like 50°F, it should heat up quickly ... Have you ever felt your batteries after flying? Warm, no? Why the problem w. flying in the cold?? I suspect it is a monitoring problem, not a battery problem. I have a LiOn battery in my riding snow blower, and it works fine down to -40°F ... AND, the manufacturer recommends at lower temps to briefly hit the start sw. and wait a few seconds, and the battery will be warm and start fine .. have never had to do that ...ALWAYS starts fine. ...
     
  12. The Editor

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    The Inspire batteries are not Lithium Ion but Lithium Polymer and the effects of low temperatures on battery performance is well documented.
     
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  13. Rich Sugden MD

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    Don't Lithium Polymer batteries heat up when under load? Mine sure seem to, even after short flights ... I know Lithium battery charge is markedly reduced when the battery is cooled down, but once they are being used they shouldn't cool...
     
  14. damoncooper

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    Yes they do but due to the Inspire's unique open body design and battery design, 4 of the 12 internal battery cells are on the outside of the pack exposed to the elements except by a very thin barrier. Coupled with the fact that these are very low C discharge batteries to begin with and the greater demands placed on them by the X5 in particular, battery voltage sags at low temps are quite common.

    In more extreme cases, LVC (low voltage cutoff), induced by low (or high) temp-related voltage sags can bring down your aircraft.
     
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  15. Rich Sugden MD

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    I wonder if it is the monitoring circuitry that may also be on the outside, is being cooled and giving a false reading ...
     
  16. Mad_angler1

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    You guys have made some great progress this year, the knowledge and understanding around the DJI packs seems to have grown massively.

    Only a good thing :)
     
  17. damoncooper

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    Update:

    I have found that using the external blanket and chemical warmers ONLY when ambient temp is < 0C will keep battery temp in the 20C - 40C optimal discharge "Goldilocks" zone if starting battery temp is 20C+. Adding the chemical warmers when ambient temp is >5C can lead to overheating, with battery temps at end of flight >45C.

    Using the blanket WITHOUT chemical warmers between 0C and 15C generally keeps things in the Goldilocks zone.

    So:

    < 0C: blanket and chemical warmers
    > 0C: blanket only
    > 15C: no blanket

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  18. damoncooper

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    Because: stickers suck
     
  19. bluethundr

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    For us that use Fahrenheit I made the degree change in F.

    " I have found that using the external blanket and chemical warmers ONLY when ambient temp is < 32F will keep battery temp in the 68F - 104F optimal discharge "goldilocks" zone if starting battery temp is 68F+. Adding the chemical warmers when ambient temp is >41F can lead to overheating, with battery temps at end of flight >113F.

    Using the blanket WITHOUT chemical warmers between 32F and 59F generally keeps things in the Goldilocks zone. "
     
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  20. damoncooper

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    The chemical warmers had no effect on compass. Hovered steady as a rock.
     
    #20 damoncooper, Feb 3, 2016
    Last edited: Feb 4, 2016