Cinestar X8 fly time problem

Discussion in 'Cinestar 8' started by Maximilian Tarpini, Apr 7, 2016.

  1. Maximilian Tarpini

    Maximilian Tarpini New Member

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    Hi there !

    I've a Cinestar X8 with the following config:
    T-Motors U5 400Kv, T-Motors Carbon CFProp 15x5, T-Motors ESC S45A 600Hz, Dji A2, Booms 50cm X8.

    Without gimbal is around 4.5kg (10lbs). Flytime: 6/7mins
    With the gimbal and a DSLR is around 9.5kg (20lbs): 2/3mins

    The problem is of course that fly times are just ridiculous.

    However they are consistent on various different packs of battery.
    For example :
    2x5800 RobbeEVO 35C ( - 2.50mins),
    2x5000 ThunderPowerRC G8ProForce 70C ( - 2.10mins)

    So I'd say it's not a battery problem. They all came with the Cinestar so I did not own them from the begining but they all charge at +25v, cells are balanced and doesn't seem to be any other shortcoming, should be just a couple of years old with less than 50/60 charges.

    However eCalc gives me around 12mins without gimbal and 6.5mins with the gimbal load.
    So what could be at this point. Or better. What would you do guys at this point... what would you start replacing/inspecting ?! Eventually what eats all the capacity of my batteries ? :)

    The only thing that looks suspicious are the ESCs. After a fly, motors are just cool but ESCs are over 70°(160F).

    Beside that Cinestar is really stable and don't have any other problem. So I'm just kinda frustrated that I cannot fly more than 2mins or so. Would be great if you can help a bit.

    Here a minimal fly if you wanna take a look.


    Thanks in advance. Ciao
     
  2. Steve Maller

    Steve Maller UAV Grief Counselor

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    What voltage are you landing at?
    I'd guess that you might also be able to run larger props on that configuration.
    I'd invest in some new batteries.
     
  3. Jason Smoker

    Jason Smoker Active Member

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    most people run 2x10000 mah batterys for that set-up. I have similar set-up 16 inch props kde-motors- 4012xf and get around the 12-15minute mark depending on payload
     
  4. Maximilian Tarpini

    Maximilian Tarpini New Member

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    Ehy thanks for the feedback guys.

    I land at around 22v. Thing is that I understand the batteries 'bounce' but after landed in some secs they get back to 23.5v. Isn't that too much of a bounce!?

    I'm waiting for some cheap hobbyking 10000mAh and for some better genace 8000mAh. Plus I ordered xrotor50a ESCs because those I mentioned above get too hot.. my feeling is that they stress too much the batteries. Is this an option at all in your opinion?
     
  5. Alex Fuller

    Alex Fuller Member

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    Sounds like a combination of old/low quality batteries plus being a little underpowered with the 15inch props/U5 motors, dont think its your ESCs. You say the batteries are pre owned, correct? That could be a culprit in that they were not properly stored/charged. Also, you can probably land a little lower closer 21V, I set my voltage alarm to 3.5V per cell. If its at 22V, sometimes thats just due to voltage sag and it will stay at 22V but still have enough mAh in the tank.

    Looking at the T Motor spec sheet for the U5s, those motors are efficiently delivering 17.44lbs (7.9kg) of thrust at a 50% throttle. If you move up to the 16inch props, that will get you 21.12lbs (9.6kg) of thrust. Try bigger props and lowering your voltage alarm to 21v. Do you use the built in DJI battery warning? I find it best to disable that function, and attach a voltage alarm on the balance port and rely on telemetry. Sometimes the DJI low battery warning will take control of the craft and land it prematurely, which sometimes could be a really bad place!

    Lastly, invest in good batteries! Tattu makes some very reliable packs, I wouldnt trust the cheap stuff with a heavy lifter like the Cinestar.
     

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  6. Cody Hanthorn

    Cody Hanthorn Member

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    Agree on the batteries for sure. I had a friend that had a DYS X8. 400kv on 15.5 props. About 880 ma per minute with new packs(DYS gimble. Cheap DYS motors, and props. Movi added for test went to 1200 per minute. Yes its a cheap frame, but I do remember that it held effieincy with the cinestars even loaded.

    The age of all our packs the capacity goes down from the first day on that we own them even though so very slightly. I also add that Tatto packs are just great. Voltage drop and capacity all degrade birds flight time. You are depending on a bird. Cheap is not an option.

    -Cody
     
  7. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Maximillian: I'm not sure what charger you are using, but will it tell you the internal resistance of the battery after you have charged it back up? If the batteries are getting old or have been mistreated before you took ownership of them, you may find that the resistance of the batteries are abnormally high. This will have the effect of causing voltage sag when you get airborne, but the voltage will bounce back when you land.

    For new packs I would expect to see between 5-10 milliohms per cell for new batteries. I suspect (from the landing voltage of 22v) that you're using 6s, so that would be no more than 60 milliohms total. If you are seeing, say 20+ milliohms per cell, those are batteries that are on their way to Lipo heaven....or hell.... :)

    Andy
    ----------
    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst
     
  8. Maximilian Tarpini

    Maximilian Tarpini New Member

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    Ehy guys, good news !

    So today finally arrived the first pack of batteries. Curiously I first ordered 2x Multistar 10000mAh at 10C(max 20C). Yeah I know however I already got around 10mins of fly, almost hovering but there was some wind at around 8 mph/h. So I'm pretty happy at the moment. With the added wait of the 2x10000, Cinestar was almost 22lbs. What you think.. ain't a good fly time ? Now I'm waiting for 2x9000 (25C) Tattu Gen Ace.

    One thing, for the records, that impacted the flytime, was lowering the min battery level to 21V as Alex kindly advised, looks really that for heavy loads, batteries get fastly down to some threshold and then take time to go lower. Btw, do you fly with auto-landing or do you prefer and advice manual landing ?

    Andy, I have a Robbe PowerPeak I'll look tomorrow if it gives me battery internal resistance that is of course something I was not considering at all, so thanks! Eventually, let's say the Robber charger doesn't have it, do you know if exist something just to measure battery resistance and alike, I guess I'd want it with me if I'll ever buy some other old battery !

    I guess that as soon the other batteries have arrived I'll try with some 16x5.4 props because it would be great to be around 12mins fly time. Btw, has a flat8 generally more fly time than an X8 ? Oh and a last little thing.. my X8 has a little tendency to low down on a straight path.. ie. if I don't touch the throttle and fly straight for 100m starting from 30m of altitude I believe I'll end at 20m. Is there a way to constrast this tendency, is it common on X8 with A2 ? I heard someone has different props size for up and down, may it help here,? and if not why having two different size at all ?

    A lot of questions, but you know looking at the wonderful advices you gave me I had to shoot a couple more !

    ciao
     
  9. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hi Maximillian:
    Yeah, there are indeed dedicated internal resistance meters. A sufficient number that it's probably the best for you to do a Google search. Just search for: internal resistance meter lipo

    Hope this helps.
    Andy
    ----------
    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  10. Maximilian Tarpini

    Maximilian Tarpini New Member

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    Yep, I think 'IR meter' is even better to find stuff.

    One last question I promise! Do you all store LIPOs at around 23V ? Last batteries I ordered arrived at 23.3V I guess that's the voltage to have them stored then, right ?
     
  11. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hope you find one you like. Please post again when you have one -- I suspect other forum members would like to know.

    The consensus is to store them at 3.85 volts per cell. So for 6S, 23.1 volts, but I don't think it's that critical -- 23.3 or 23 volts won't matter. Just do not store them fully charged or discharged for days on end, and certainly don't take them down below 3.0 volts otherwise they tend to switch to "paperweight mode." :)

    Andy.
    ----------
    Forensic Software & sUAV / Drone Analyst : Photographer : Videographer : Pilot (Portland, Oregon, USA): Trees=2, Ground=1, Props=11. :(
    The Ground Is The Limit™
    ---------- Forensic Drone Analyst : Forensic sUAV Analyst : Forensic Unmanned Aircraft Analyst : Forensic Drone Expert
     
  12. Maximilian Tarpini

    Maximilian Tarpini New Member

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  13. Steve Maller

    Steve Maller UAV Grief Counselor

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    That one looks like a bit of overkill. This one looks better/cheaper.
    http://www.hobbyking.com/hobbyking/store/__10328__HobbyKing_8482_Battery_Medic_System_2S_6S_.html
    Truth be told, you're better off getting a better charger, as the static meters like these can only tell you a little bit about your batteries. The best information you can get is by observing the actual charge cycle.
    What charger are you using?
     
  14. Maximilian Tarpini

    Maximilian Tarpini New Member

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    It's a professional Robbe PowerPeak with EQ-BID build-in. Just checked, it has a 'Data view mode' while charging so I can check batteries single cells stuff etc. but there's not an internal resistance meter. The one you posted doesn't have it either. I'm looking for one as Andy introduced me to this 'internal resistance' stuff I wasn't aware of. So I can check old batteries and see why they have so low performance.

    http://www.conrad.com/ce/en/product/238625/POWER-PEAK-quad-EQ-BID-230V
     
  15. Shaun Stanton

    Shaun Stanton Active Member

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    You can push the load voltage down to 21V The min load voltage is 20.4. You do not want to shoot for that number. I usually try to get it on deck at about 21.3V

    Yes the voltage sags under load. The heavier your payload the quicker it will sag. It is normal to see the differential between 22 and 23.5V after landing.
     
    Steve Maller likes this.
  16. Maximilian Tarpini

    Maximilian Tarpini New Member

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    Sounds reliable. Btw, do you use safe-landing or are you all manual !? Cheers
     
  17. Shaun Stanton

    Shaun Stanton Active Member

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    I fly DJI so its sorta manual in a mode called Atti except it has altitude hold on continuously.
     

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