Another Flight Time Thread

Discussion in 'Cinestar 8' started by Josh Conley, Apr 9, 2013.

  1. Josh Conley

    Josh Conley New Member

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    Sorry to ask the question you all have seen to many times. I'm getting 8min flying my CX760 got another gimbal to be able to fly my 5D Mark iii (canon 14mm USM II lens) without the frustration of balancing the camera and gimbal and now I'm getting 4:30min. Those flight times seem low compared to what i'm seeing on this board. Can anyone with similar setups comment? I have included logs flying both payloads. Andy?

    CS8
    QC-3328 motors
    MK electronics
    FF 3 axis gimbal
    4S 8000mAh
     

    Attached Files:

  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Josh:
    I ran MK_GPXTOOL for you on the two GPX files.

    The first file (they both have the same file names) shows that the battery went from 16.3V to 14.5v, consumed 6,777 mAh, and the flight lasted 7 minutes 55 seconds. This was on 2013-03-12.

    The second file shows that the battery went from 15.9v to 14.4v, consumed 5,217 mAh, and the flight lasted 4 minutes and 20 seconds. The flight was on 2013-04-09 (today).

    For the second GPX file, the initial battery voltage is only 15.9v -- typically, what I see is that the initial maximum voltage is 16.1v or thereabouts -- bearing in mind a fully charged battery 4S that is not connected a load will be 16.8v or thereabouts.

    The log file doesn't start until you open up the throttle so the copter is at takeoff power, so the voltage sagging to 16.1v seems "normal."
    Not sure why the battery sags to 15.9v so quickly though.

    Can you tell us anything about the battery you were using? Was it the same battery for both flights? How has it been stored between the flights (presuming that it was stored and you didn't fly in between these two dates)?


    The summaries are at the end of this posting.
    Andy.




    First file:
    MK Version: FC HW:2.1 SW:0.88n + NC HW:2.0 SW:0.28p​

    Flight date: 2013-03-12 11:02:17 AM​
    Flight time: 11:02:17 AM - 11:10:12 AM (475 secs, 00:07:55)​
    Batt. time : 473 secs, 00:07:53​

    Elevation(GPS) : 0 13.98 48.652 m (min/avg/max)​
    Altitude(Barom.): -1.3 15.45 53.05 m​
    Vertical speed : -2.98 -0.01 2.5 m/s​
    Max speed : 18.3 km/h​
    Max target dist.: 0 m​

    Sats : 10 11 13​

    Voltage : min. 14.5, max. 16.3 V
    Current : 8.6 51 73.2 A​
    Wattage : 127 787 1098 W​
    Capacity: 6777 mAh​

    Motor1: 3.3 5.6 8.7 A Temp: 12 41 50 °C​
    Motor2: 3.7 5.8 9.8 A Temp: 13 39 48 °C​
    Motor3: 2.0 4.1 6.8 A Temp: 16 32 44 °C​
    Motor4: 2.2 6.0 9.3 A Temp: 13 35 45 °C​
    Motor5: 1.5 4.7 7.5 A Temp: 14 37 48 °C​
    Motor6: 3.3 8.6 11.7 A Temp: 13 50 66 °C​
    Motor7: 2.0 6.1 10.0 A Temp: 15 55 68 °C​
    Motor8: 1.8 8.8 12.6 A Temp: 15 61 78 °C​

    Magnet Field: 105 108 111 % (ok)​
    Magnet Inclination: 59 62 74 deg​

    Errors / warnings:​
    I2C errors: 066​


    Second file:
    MK Version: FC HW:2.1 SW:0.88n + NC HW:2.0 SW:0.28p​

    Flight date: 2013-04-09 6:31:11 AM​
    Flight time: 6:31:11 AM - 6:35:31 AM (260 secs, 00:04:20)​
    Batt. time : 281 secs, 00:04:41​

    Elevation(GPS) : 0 11.56 40.697 m (min/avg/max)​
    Altitude(Barom.): 0.4 14.78 45.25 m​
    Vertical speed : -3.24 0.04 2.16 m/s​
    Max speed : 11.4 km/h​
    Max target dist.: 0 m​

    Sats : 7 7 8​

    Voltage : min. 14.4, max. 15.9 V
    Current : 10.2 67 84.8 A​
    Wattage : 152 1015 1221.12 W​
    Capacity: 5217 mAh​

    Motor1: 0.7 6.3 8.8 A Temp: 20 50 65 °C​
    Motor2: 6.9 9.0 12.1 A Temp: 20 56 73 °C​
    Motor3: 5.5 6.4 8.0 A Temp: 22 51 62 °C​
    Motor4: 0.6 9.8 12.7 A Temp: 22 64 79 °C​
    Motor5: 0.4 6.3 8.6 A Temp: 22 54 65 °C​
    Motor6: 0.6 10.5 12.6 A Temp: 26 69 82 °C​
    Motor7: 1.9 6.8 8.4 A Temp: 26 71 84 °C​
    Motor8: 3.4 10.5 13.6 A Temp: 28 74 95 °C​

    Magnet Field: 109 109 112 % (ok)​
    Magnet Inclination: 55 56 61 deg​

    Errors / warnings:​
    I2C errors: 062​
     
  3. Josh Conley

    Josh Conley New Member

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    Hi Andy,

    The battery used in the first flight was a quadrocopter 4s 8000mAh flown with the cx760 payload. The second was a virgin freely 4s 9000mAh flown With the mark iii. I have constantly noticed batteries sagging at the beginning of flights but it seems to be exponentially worse with the heavier payload. I have 10 - 15 flights each on 6 different 8000mAh batteries and the results are relatively consistent 8min to 14.4v witht the cx760 payload. The 6 flights I did today one with 9Ah and 4 with 8Ah batteries with the mark iii payload were also consistent at the 4 to 5min. I should also mention I'm using the APC 14inch 4.5 props. Are you running the same battery setup on your rig? What flight times are you experiencing?
     
  4. Jason Smoker

    Jason Smoker Active Member

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  5. Dave King

    Dave King Well-Known Member

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    Motor 8 temps on your copter indicate to me that your copter could be a little more balanced. I have done a ton of testing with CG suspended on my ceiling as well as checking it in flight with the balance function of MK tools. If you are seeing temps over 90 degrees I would suspect that it's not quite as balanced as it can be. I found the process to be quite tedious but rewarding if you get it right. I"m getting about 11-12 minutes out of my C8, 3 axis gimbal, sony 760 setup running two QC 6200 batteries. The key is the get the copter as balanced as possible. I noticed that the battery placement on the plate is extremely critical and even with velcro can't prevent the batteries from moving around. The heavier the copter the more critical the CG is. I've made guide rails that can slide up and down on my battery plate that allow me to put the battery at the exact same spot on the plate every time. I also balance the CG of the gimbal so that its very balanced regardless of the camera tilt, or roll. I then double check the CG of the copter with the gimbal on it to make sure everything is still balance.d The more you hover the more I notice it will consume battery power as well.
     
  6. MIke Magee

    MIke Magee Active Member

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    Hey Dave, could you share a shot of your battery guide rails?

    tx,m
     
  7. Dave King

    Dave King Well-Known Member

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    Sure, I'll snap some shots in the next day or so.
     
  8. Dave King

    Dave King Well-Known Member

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  9. Josh Conley

    Josh Conley New Member

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    Thanks Dave and Mike,

    I have spent many hours balancing my gimbals but have spent no time balancing my copter. Do you have any suggestions on balancing such as suspend the copter from a point on the battery tray, use the battery to CG, move components to CG. I like the battery rail idea and will be buying some xoar props.
     
  10. Dave King

    Dave King Well-Known Member

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    What I like doing is balancing the copter with no batteries, then balance the gimbal by itself, then attach the gimbal and doublecheck everything together. When I balance the CG of the gimbal I balance the pan and the tilt and then check the CG. Often I will either make small changes to either one of these factors and it will throw off the other parameters so its a slow back and forth process to balance the gimbal. I then double check the CG of the gimbal with the camera mount in different pan positions as well as different roll and tilt positions to make sure the CG pretty much stays balanced regardless of the position.

    Afte the copter with the gimbal is set, I will add the batteries in and make sure the CG is good. It works well for me.

    Here's a thread that I posted describing how I balance my rig. I have a ceiling that uses recessed can lights that have hooks on them that I can easily attach fishing line too. I made an alunimum plate with a hole in the dead center of the copter which is the mounting point of the rig. http://forum.freeflysystems.com/index.php?threads/my-home-made-copter-balancing-rig.924/#post-11915
     
  11. Steve Maller

    Steve Maller UAV Grief Counselor

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    I'd consider running dual batteries in parallel. You'll have more weight, but you'll have twice the power and will have failsafe redundancy in case one battery screws the pooch in the air. It happens. :eek:
     
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  12. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Alternatively, you have doubled the chance of a failure! :)
    If the failure is that battery shorts out, then you've actually doubled the chance of a crash as the bad battery will take the good one (and the copter) down!

    That said, I don't know whether LiPo's fail by shorting out -- anyone know?

    Andy.
     
  13. Joe Azzarelli

    Joe Azzarelli Active Member

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    I am sold on dual batteries in parallel. Voltage drop-off is more gradual, giving you more time to get home and the batteries are much cooler at the end of the flight.
    Also, get two of these alarms - one for each battery. They beep LOUDLY when any cell dips below the adjustable voltage level.
     
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  14. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Based on the results of the Rather Good Guide I did on LiPo's I have to agree. Dual batteries deliver more than 2x the capacity of a single battery. As you say, Joe, they stay cooler (and, from my observations, are called upon to deliver a lower current) and that seems to be a Good Thing.

    Andy.
     
  15. Josh Conley

    Josh Conley New Member

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    Thanks for all the input. It seems most dual setups I see run 6000mAh. Can anyone shed light on that for me? Anyone running two 8000mAh batteries?
     
  16. Steve Maller

    Steve Maller UAV Grief Counselor

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    I only run 8000mA batteries, and I run two at a time. Quadropowers and Zippys (but in matched pairs). I fly them and charge them together.
     
  17. Josh Lambeth

    Josh Lambeth Well-Known Member

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    I was running dual 8000mAh 5s for a while before I switched to 6s.

    Josh
     
  18. Josh Conley

    Josh Conley New Member

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    Per Dave's suggestion I did some balance checking in MK tools and the first thing I noticed was the yaw measurement on the balance screen of the CS8 was running between -10 and -20. Is anyone else out there checked to see what there copter is having to do for yaw correction? If all the motors are perfectly vertical, what else would you check to get the yaw correction closer to 0? (Example image attached not actual while flying)
     

    Attached Files:

  19. Gary Kaplan

    Gary Kaplan New Member

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  20. Gary Kaplan

    Gary Kaplan New Member

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    A single 4S 8000mAH LiPo has the same capacity a (2) 4S 4000mAH LiPo's connected in parallel. The voltage stays the same but the current capacity is doubled. It would take (2) 2S 8000mAH LiPo's connected in series to have the same voltage and capacity as the previous examples. The batteries capacity stays the same but the voltage is doubled. In a parallel configuration you can (although not recommended) use two batteries with different discharge ratings because if one battery cannot source enough current to the motor when called on the one with the higher dicharge rating will do so. In a series connection (2-2S 8000's) you MUST match the discharge ratings of both batteries because current is drawn from one battery and through the other (- to + to - to +) inline. If one battery has a lower discharge rating than the other then the one with the lower discharge rating will heat up as the higher current amount sourced by the battery with the larger discharge capability gets pulled through it. The result at best will be a ruined battery and at worst it will be an exploded battery and possibly a copter on fire.

    If you look at the specifications of the Quadcopter battery (below) you will see that it is actually (2) 4S 4000mAH batteries connected in parallel inside the package. The label says "8000mAH" and it is at the two leads (black and red) coming out of the battery, but inside the package it is (2) 4S connected in parallel.

    Quadropower 4S 8000mAH Technical Info:• Capacity: 8000+ mAh 4S2P <--- this spec says "4S battery connected in a 2Parallel configuration
    • Voltage: 14.8V (4S)
    • Size: 146*44*40mm (L*W*H)
    • Weight: 823g
    • Discharge rate: 30C continuous; 50C maximum <--- this is the specification that matters the most. It tells you how much current the battery can source to the motor. It can source 30Amps continuously (meaning it wont exceed it maximum temperature rating) and can source a maximum of 50Amps for short bursts of speed or under heavy load with a camera(usually a 15 sec. burst after which you have to back off the throttle to let it cool before attempting it again).

    The reason some batteries run cooler than others (and have less cell voltage sag) is because they have higher C rating. They can source more current continuously as well as provide more under heavy load without getting hot. Also, they will maintain their cell voltage even as the capacity (current) is drained out. A very good battery will have a cell voltage of 3.5~3.7V even if you run the battery almost out of currrent (even below 1/3 of total capacity remaining).

    For example, these Nano-tech batteries have a 65C~130C rating. They will provide 65Amps continuously and up to 130Amps under burst or load! Also, not the battery configuration. Its a (1) 6S battery (meaning there are (6) 3.7V cells inside) connected in a single parallel connection. The same thing holds true if I used a 4S battery example.

    http://www.hobbyking.com/hobbyking/...y_nano_tech_5000mah_6S_65_130C_Lipo_Pack.html
    Turnigy nano-tech 5000mah 6S 65~130C Lipo Pack: Spec.
    Capacity: 5000mAh
    Voltage: 6S1P / 6 Cell / 22.2V <--- Its (1) 6S pack
    Discharge: 65C Constant / 130C Burst <--- This is what you want. It can source 65A all day without breaking a sweat.
    Weight: 844g (including wire, plug & case) <--- This is the trade-off (nothing good comes for free). Its a bit heavier than the 8000mAH Quadropower and less airtime. BUT it will last a long time and will take a lot of charge/discharge cycles before it starts to degrade and its a lot cheaper. You can always put (2) 4000mAH packs together in parallel if you absolutely need the airtime of a 8000mAH battery. I guess it depends on the kind of flight you need/want.

    Cheers,
    Gary K.
     

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