One battery or two? 10000 or 16000 or 22000?

Discussion in 'Batteries & Power' started by Derek Cooper, Sep 16, 2014.

  1. Derek Cooper

    Derek Cooper Active Member

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    Is there a formula somewhere that helps determine the ideal battery solution for Cinestar X8 copters?

    At some point there is a weight / performance trade-off with the higher capacity batteries?

    Curious how people decide.
     
  2. Tristan Twisselman

    Tristan Twisselman Active Member

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    It really depends on your target auw and how much weight in batteries your copter is capable of carrying. You want to hover at 50% throttle in manual mode. For my copter that carries the M5 I am going to run 2 6s10000 and have been running 2 6s9000. If I where to want to run the bigger 16000 packs then my hover throttle would be higher than I want it to be. Sure it would work and I could probably fly a little bit longer but I rather have the shorter flight time and better power to weight ratio. My next copter will be flying 2 6s16000 or even 2 6s22000 but it will be built with that in mind.

    For you I would suggest 2 6s10,000


    EDIT: This is my opinion and everyones is different of course, but this is my take on it.
     
  3. Derek Cooper

    Derek Cooper Active Member

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    Is this logic sound?

    10,000 Mah 6S provides 12 minutes of flight time. Will 2 10,000 Mah 6S in parallel provide say 80% more (20% loss due to extra payload estimate)?
     
  4. Tristan Twisselman

    Tristan Twisselman Active Member

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    No, it depends on your heli setup. Adding anymore battery at all could make your flight time go down or go up a tad but then be hovering at too high of a throttle percentage.
     
  5. Derek Cooper

    Derek Cooper Active Member

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    Can you expand on that?
     
  6. Derek Cooper

    Derek Cooper Active Member

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    I guess this is what I don't understand Tristan - you said to go with 2 6s10,000 just above. But now you're saying "No," so I've lost you! :)
     
  7. Gary Haynes

    Gary Haynes Administrator
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    Derek have you tried using www.eCalc.CH to model some of the systems you're thinking about building. It will allow you to plug in different variables to see what the effect would be when you're set up.
     
  8. Derek Cooper

    Derek Cooper Active Member

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    Excellent - exactly what I needed! Thanks Gary.
     
  9. Derek Cooper

    Derek Cooper Active Member

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    What a terrific tool Gary - many thanks! The models don't work for X8 configs

    However the modelling does appear to be pretty close when using the flat 8 config. Very interesting.

    10,000 6S - 11.6 min hover
    22,000 6S - 21.4 min hover

    For my build based assuming flat 8. Wonder how the coax impacts the numbers... more research. But this basic modelling is what I needed.
     
  10. Sam Fleishman

    Sam Fleishman Member

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    Hey Derek,
    I contacted Ecalc and they told me to calculate for an x8, add 20% to AUW. You'll find people quote numbers from 10-30% in efficiency loss with an x8 versus flat 8. You also only have 4 arms instead of 8.
     
  11. Derek Cooper

    Derek Cooper Active Member

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  12. Sam Fleishman

    Sam Fleishman Member

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    Sorry about that. All up weight.
     
  13. Derek Cooper

    Derek Cooper Active Member

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    Excellent.

    So an X8 loses on efficiency but gains on stability?

    Performance data uses eCalc is very promising for the 22,000 mAh cells. Good options. Will look closely at 2x10,000 in parallel too.
     
  14. Sam Fleishman

    Sam Fleishman Member

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    You will be better off running 2 lipos in parallel rather than 1 big one. With 2 in parallel they share the amperage load and give you some redundancy. You need to have 2 cables running off of the power distribution board though. Just adding a parallel cable still means all that current is running through a single EC5 connector.
     
  15. Derek Cooper

    Derek Cooper Active Member

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    Interesting - I hadn't thought of that approach. And the MK Double Quadro Cool will "understand" two power sources? Instead of wiring the batteries in parallel?
     
  16. Sam Fleishman

    Sam Fleishman Member

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    It's been a long time since I've used mikrocopter so I don't know exactly how your board is wired up. Take a look at the freefly esc and pdb kit at quadrocopter.com to see what I mean. The batteries are in parallel.
     
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  17. Ryan McMaster

    Ryan McMaster Active Member

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    Two batteries are almost a must from a safety standpoint. When you have a cell drop from a single pack it could cause you to lose the whole rig. Two batteries will let you catch the cell drop and still bring it home. I don't fly without two packs since the batteries are the weak point in the chain.

    My Flat HL octo can easily fly two 10ks at 50% with payloads as large as the BM4k and Teradek downlink.
     
  18. Gary Haynes

    Gary Haynes Administrator
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    Derek the FreeFly PDB does not use a Y connector. The batteries, like most dedicated PDB's, are wired directly to the PDB and are then in parallel. Were you saying that parallel was a bad idea?
     
  19. Ryan McMaster

    Ryan McMaster Active Member

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    Gary,

    He is referring to using dual cords into a MK board, which is a very bad idea.
     

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