Very low flight time

Discussion in 'Cinestar 8' started by Anders von Holck, Apr 17, 2015.

  1. Anders von Holck

    Anders von Holck New Member

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    Hi.

    I have a cinestar HL8 with 4012 t-motors and 15*5 props. I run all MK boards (newest).

    I use the QC 10.000 mAh 6S bats but with no extra weight (no gimbal, no camera) i only got around 8 - 10 min flying time.

    Today i put on my movi m10 and a RED camera. My combined weight was around 10 kg (i know its a lot for the motor/prop setup but should do) All i got was approximately 10 seconds of flying time before the alarm started buzzing and it started to descent.

    I read about people that get 15 min with gimbal+camera so i simply dont know what i am doing wrong.

    I charge the QC Bats with the hypirion charger. I was told by QC to set it to 10.000 mAh 6S 5C

    (when i checked the voltage on the bats after today. two was discharged to 18,5 - 19 V but two of them had only been discharged on a single cell. Where the rest of the cells still had 3,7 Volts.)

    I am confused so i hope someone can help me.
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    A 6S LiPo that's reading 18.5-19V at rest (not under load) should not be flown. It sounds a lot like you have a defective or damaged battery. DO NOT fly this battery again.

    6S LiPo batteries should charge up to 25.2V, and should be considered fully depleted (not damaged, just normally used and ready to recharge) at approximately 21-22V. Any lower than that and you begin to risk damage. And the loaded voltage is always going to be lower. Are these brand new batteries? Do you by any chance have a LiPo meter on them? I've found that some LiPo meters can cause batteries do discharge unevenly and can actually damage them if left on for long periods of time (days).
     
  3. Anders von Holck

    Anders von Holck New Member

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    I have always been told (and read) that a 6S max capacity is 22,2 and that you should stop flying at 19 V. Is this wrong?
     
  4. Steve Maller

    Steve Maller UAV Grief Counselor

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    That's wrong.
     
  5. Tim Sessler

    Tim Sessler Active Member

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    A fully charged cell is 4.2V, that will give you 25.2V for a 6S pack - I have my low voltage alarm set to 3.6V/cell or 21.6V, which will give you plenty of time to land before you hit 21V (or 3.5V/cell). Technically you could probably fly even until 3.2 or 3.1V per cell but it would be way too risky as all LIPOS (expensive or cheap doesnt matter) will have a fairly extreme voltage sag at some point. 25-21.6V seems like a very moderate and safe option to fly.

    22.2V is only the resting/storage voltage of a 6S pack - most definitely not the max load.

    Hope this clarifies it a bit :)

    Cheers!
     
  6. Anders von Holck

    Anders von Holck New Member

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    It really does and thanks a lot ! It must explain why i had trouble flying today but now i hope i havn't ruined any of the battery, i ran 4 bats down to 18,5 - 19 :(
     
  7. Dave King

    Dave King Well-Known Member

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    Hi Anders

    Sorry I just got your PM and saw this message. AS the others mentioned the batteries have to be properly charged. If you run the batteries too low they are essentially paper weights as they either won't charge again or hold a charge properly. I usually set my low voltage warning to come on at 21.6 and I am landing no lower than 21.0 to 21.1 volts. Once you land the load is off the batteries the battery voltage should come back up to around 22 volts if you do this correctly.

    With no load and landing gear I was getting close to 30 minutes flight time and can get 16 minutes easy with the 4120 heavy motors carrying 25-26 pounds. I also want to stress that this is with 2 10,000 batteries. I think you are running only one battery? That makes a big difference.

    My recommendation is to start datalogging and making sure everything else looks good with no errors. Check your motor currents and make sure they are pretty level. If you have a motor out of alignment or your COG is not setup correctly it will skew things a lot.
     
  8. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Anders: You wrote "I charge the QC Bats with the hypirion charger. I was told by QC to set it to 10.000 mAh 6S 5C"

    Can you clarify what charging current you set the Hyperion to, please?

    I think setting it to 5C (that is 50 Amps) is too high. I would suggest, if you are not in a hurry, go for 1C (10 Amps), or perhaps 2C (20 Amps).

    Andy.
     
  9. Shaun Stanton

    Shaun Stanton Active Member

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    22.2 is the no load resting min voltage. The lowest voltage under load is around 20.3-20.1 depending on flight mass. I found that carrying 13 pounds I only have 45 seconds to be on the ground at 20.3 before the copter hits 20.1 min load voltage. To understand how batteries work. The lower the voltage sag the more current is being pulled due to having equal power P=VI. once you hit 20.1 the battery will start accelerating its current pull to unsafe levels and potentially causing a thermal runaway and possible fire.

    I would consider all your batteries that went below 20V as unsafe and unreliable. The ones that discharged only oned cell are damaged and not reliable for flight and unsafe to even attempt charge. I would discharge those batteries and never use them again.

    I just had a 6S 10,000 QC battery do that to me on the charger recently. It had an internal resistance of .450 mW. This means that in theory the battery was absorbing 12 to 14 Amps internally which is not good at all could have resulted in a fire if I did not catch it in time. Luckily I found it on the charger and not in flight. I have had it happen flight on an old 4S CS8. I charge at 1/2C most of the time and 1C if and only if I don't have time. I tried a 5C charge once it does not put in the full capacity, I notice that the battery gets to min load voltage quicker.
     

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