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Cold Battery

Discussion in 'Phantom 2 Vision Discussion' started by grochester, Mar 1, 2014.

  1. grochester

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    I learned the other day that the decline in battery power in cold weather is not linear, it seems exponential. I discovered this when flying low under the overhang of a grove of trees on a very cold day my battery quickly declined. The P2V first tried to land on its own without going up. It was only about 30 feet away from me so I thought I could fly it back. The alternative was to land it in deep, powdery snow and I didn't want to fill it up with snow. While trying to fly back it switched to RTH mode, and wanting to be at 60 feet altitude, shot up into the trees. No damage other than 3 broken props. BTW, when it decides to come home it goes up in a hurry.
    What's interesting is how quickly the battery went away. I had started the flight with a warm battery, having had it in the house. I think the propwash in cold weather really cools the battery down in a hurry. The lesson learned is that in really cold weather when the battery is at 50 percent you want to be pretty close to home, because the other 50 percent is not going to last for long. It's not linear.
     
  2. ClimbrJohn

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    While I agree with your post... how cold is 'really cold'. I've found unless I'm flying below 20ºF I seem to have about the same battery performance. However, I haven't really flown much warmer than 60ºF.
     
  3. grochester

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    Really cold is in the -20C range. Below that it's just not fun.
     
  4. FSJ Guy

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    YIKES!

    Yes, -20C is REALLY COLD!!!!

    Anything approaching -5C and I don't fly. LOL!
     
  5. OI Photography

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    Any idea what triggered RTH when it was that close to you?
     
  6. FSJ Guy

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    Depends on how you have it programmed. You can tell it to auto land with a low battery warning or RTH on a low battery warning.
     
  7. OI Photography

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    You can change the behavior for when failsafe is triggered, but I don't believe the NAZA will let you set RTH for a voltage warning (Wooking will though).
     
  8. Pull_Up

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    That's right, only option in the Vision is to make failsafe either standard RTH, or simply autoland out. Pushing the sticks hard can cause a voltage drop big enough to start a low battery autoland, but there seems to be a short delay before it kicks in, and relaxing a bit of stick pressure can bring things back to normal. But this is all based on my observations and I haven't been out in anything much below freezing...
     
  9. rnrnrn

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    I can't confirm the temperature since my lowest was around +5degC - but this behaviour with RTH with low battery level is a bit alarming though. I just did double check the options - and yes you can configure autolanding or RTH only when failsafe is triggered - but that's only when the connection is lost.

    Nonetheless loss of connection in that kind of temperature would not be out of the question - it is beyond the scope of the official working temperatures. And thanks for the battery drop warning - I would not have assumed it could drop like that so fast.

    It would be good if someone could confirm any strange behaviour in such low temperatures - it would be good to know just in case.