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Lipos for HL 4S 5S 6S? 4S runs way cooler!

Discussion in 'Cinestar 8' started by Chris Newman, Sep 14, 2013.

  1. Chris Newman

    Chris Newman Member

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    So I built a heavy lift.
    wookong, cinestar frame, axi 4120/14, 15inch xoars

    I did test with a 8lb dumbbell as payload. I flew 2 5S 8000mah 25-50C lipos tempture of the battery / escs was 135-140F.
    I then flew the same 8lb payload with 2 4S 9000mah 25-50C lipos and the temperature of the Batteries / escs was around 100F!

    Should I be concerned with the 140ish temp? What are the benefits of higher cells? I didn't seem a huge notice in copter maneuverability power.

    I'm tempted to just use primarily 4S because of the cooler temps. Any reason why I shouldn't?
    Thanks in advance!
     
  2. Gary Haynes

    Gary Haynes Administrator
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    Chris that sounds abnormally high. Have you modeled your setup in ecalc to see what it indicates?
     
  3. Chris Newman

    Chris Newman Member

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    Everything seems to check out I believe. It puts the 5S at being 15F warmer than the 4S. I think my weight might be off though I put my AUW in the "Model weight" category and I think it's adding the battery / motor weight on top of that? Eitherway I don't see any red flags in ecalc.

    Should model weight be the weight without esc, motors and batteries?
     

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  4. Gary Haynes

    Gary Haynes Administrator
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    Model weight incl drive, it's usually the default. Also you have a better throttle percentage with the 5s. Maybe Andy can comment on the temps. Did the 5s puff up at all?
     
  5. Chris Newman

    Chris Newman Member

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    So I did it correct or not? Thanks gary I'm an ecalc noob. What do you think of the results, anything stand out?
     
  6. Gary Haynes

    Gary Haynes Administrator
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    They look correct. 5s is better since the hover throttle is lower but that doesn't explain the batters ay those types of temps. Did they puff up?
     
  7. Chris Newman

    Chris Newman Member

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    Yeah, they were kind of puffy. I was using Turnigy, could that be why?
     
  8. Gary Haynes

    Gary Haynes Administrator
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    Which Turnigy? They have a whole bunch of sub brands. And if they puffed noticeably they may be shot, as in no longer usable.
     
  9. Tyler Olson

    Tyler Olson Member

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    how are you using 4s (16.8V) and 5s (21V) batteries on the same copter?
     
  10. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Chris:
    If you have batteries that are reaching 135F, then they are pretty much toast (or about to be).

    For example, Maxamps, who makes LiPo's state that the maximum operating temperature of a LiPo should be 140F (60C), so you're getting dangerously close. This same number is also cited by Lockheed Martin. http://www.lockheedmartin.com/conte...s2/documents/procerus/LithiumPolymerUsage.pdf
    Mind you, they also say "Never plug batteries into each other." (So much for dual batteries and paracharging.)

    I think you may need to dispose of them. Thunderpower's disposal instructions are at http://thunderpowerrc.com/PDF/DISPOSAL-OF-LIPO-BATTERIES.pdf

    There are numerous other examples, e.g. https://sites.google.com/site/tjinguytech/charging-how-tos/lipo-disposal

    Many seem to recommend the "salt water drowning" approach, but I really have no idea whether this is necessary. Certainly if you can take the voltage down to 0 volts and make sure the voltage does not rebound over 24 hours, the LiPo is inert. The problem seems to be that to go from 2 volts to zero can cause the battery to heat up badly if you do it too fast.

    Whatever you do, do it outside any buildings, use a LiPo bag and simply assume that it will burst into flames before you're done.

    Andy.
     
  11. Steve Maller

    Steve Maller UAV Grief Counselor

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    Sounds iike my BBQ technique.
     
  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Ha! Yeah. Except that for me there's another rule at work: The coals on a barbeque are always at their best when you've finished cooking.

    Andy.
     
  13. Chris Newman

    Chris Newman Member

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    Im flying wookong m.

    They are not that puffy. Theses are the ones. http://www.hobbyking.com/hobbyking/store/__18209__Turnigy_nano_tech_8000mAh_5S_25_50C_Lipo_Pack.html

    Hey Andy, Yeah they are getting warm. They are new batteries, would a higher C rating be the way to go to cool things down? I'm not plugging 2 batteries directly into each other, but 2 ec5 connectors going into the same distribution board.
     
  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    The higher C ratings should improve matters. In my experience you don't want batteries that are hot -- warm is ok, but hot is bad news.

    Andy.
     
  15. Gary Haynes

    Gary Haynes Administrator
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    Chris how about a couple of photos for the puffy view.
     
  16. Chris Newman

    Chris Newman Member

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    The Batteries are not puffy just get a little soft after flight which is normal. I've been flying them on shoots and since I don't use the entire battery at one time my temps stay around 100F. I did have one battery however that had the connector come unsoldered. Luckily the second battery took up the slack until I could land. That battery is definitely puffy and will be put out of commission. I also bought some 65C batteries that i'm experimenting with.
     
  17. Graydon Tranquilla

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    Benefits or higher cell count...... In an effort to remain in the sweet spot for electric motor efficiency the higher horsepower motors must be designed to work with higher voltage level versus simply increasing the current draw. Simply increasing current draw results in lower motor efficiency and evidence of lower motor efficiency first appears as waste heat!
     

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