E-Power 101

Discussion in 'General Plane Discussion' started by TManiaci, Sep 5, 2008.

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  1. Mar 4, 2014 #101

    TManiaci

    TManiaci

    TManiaci

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    Do you know the actual fresh battery peak (WOT) amp load?

    You say you are flying a 6S5000, is that 6S1P or 6S2P? (which pack are you using specifically?)
     
  2. Mar 4, 2014 #102

    JeffinTD

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    A friend of mine had one of those, and I believe he ran 2 3300 3s packs in series with good results.


    One thing that hasn't been mentioned that I find helpful with electrics is running a Li-Po Alarm.
     
  3. Mar 4, 2014 #103

    Jace

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    Spec.
    Minimum Capacity: 5000mAh
    Configuration: 6S1P / 22.2v / 6Cell
    Constant Discharge: 20C
    Peak Discharge (10sec): 30C
    Pack Weight: 765g
    Pack Size: 145 x 50 x 50mm
    Charge Plug: JST-XH

    Discharge plug: 4mm Bullet-connector

    That's the current battery. I can get the nano technology 3000 and it comes in at 447g. Over 1/2 a pound lighter
     
  4. Mar 4, 2014 #104

    JeffinTD

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    What sort of flight times are yiu gettig out of the packs you are using now?
     
  5. Mar 4, 2014 #105

    Jace

    Jace

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    I set a 8 minute timer and I usually put 2500ish back into them. So I think I can get away with a lighter battery
     
  6. Mar 4, 2014 #106

    JeffinTD

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    Yeah. It looked like 3200 mah was recommended, so I think yiu are on the right track. Running a beeper alarm could help take the guess work out of flight times without running the packs down to lvc.

    I have the Reactor Bipe with a Rimfire 80 and it runs on 3300 6s. I also have the big Reactor with 50cc gas. Both are nice fliers, and I suspect yours will be too, when you fly it with a lighter battery.

    Looks like all but the big one were recently discontinued.
     
  7. Mar 4, 2014 #107

    TManiaci

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    The calculation says you have a 10 minutes flight. That specific setup should draw 50 amps peak according to the e-Flite website. That is a critical ingredient in the sizing of a power system.

    I am at work now, but I'll look at this closer later in the day and share my thoughts.

    If you are willing to give up some flight time, you definitely have some room to get lighter with smaller packs.

    The other option is to push your setup to the next level with more propeller. You have the capacity to go to 65 amps. Some calcs can steer you to a few to try, but you may want to get an Watt Meter so you can assure the proper setup is running.

    The question is this; is the airplane flying "heavy" on the wing, or is it just sluggish and needs more power?

    That has a bearing on this math. The ideal solution would be to do both, more prop and less battery. The best 3D performance would come with that mix of adjustments. As with any e-system, you would be running on the fringes of the ratings, understanding that you would only slam it hard periodically for short periods. That's how you get the most out of a system.
     
  8. Mar 4, 2014 #108

    Jace

    Jace

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    I don't have problem giving up some flight time. My problem is I want a little electric I can fly at my house, but fly like 30% pilot Rc yak. Nice and floaty but have the power.

    On the props I've ran so far. 14x10. 15x10. 16x8. The 16 is the best so far.

    The plane flys heavy. Very poor low and slow performance. Lots of wing rock. It will hover but at 3/4 to 5/8 throttle. And not much pull out.

    They have discontinued the small reactors and that's also got me thinking maybe I should switch to a new airframe. 59" 3DHS slick or 60" 540 from EF.
     
  9. Mar 4, 2014 #109

    TManiaci

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    Is your Power 60 the 400 kV or the 470kV version?

    Looks like you can try the 17x6 to 17x10, and maybe even 18x6. You want more diameter, less pitch for 3D flying. Check your ground clearance, and you may need a different prop adapter.
     
  10. Mar 5, 2014 #110

    Jace

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    I believe its the 400kv but i'll look when I get off work.
     
  11. Mar 5, 2014 #111

    BRUTUS

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    Just like old times. :thumbsup:
     
  12. Mar 5, 2014 #112

    Jace

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    Ya its the 400kv motor. For the prop choices with the 16 on there now I have to 3 point land. I have about an inch when the tail wheel comes off the ground
     
  13. Mar 5, 2014 #113

    JeffinTD

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    I'd bet a high c rated 3300ish pack, and maybe a bit more prop will make a huge difference in how the plane flies. Just seat of the pants, I would think the 5000 would be too much on the weight vs flight time scale, and you'd be happier with 6 minute flights with lighter wing loading than having a setup that could fly 9 minutes but flies heavy.

    Just my non-expert $.02.
     
  14. Mar 5, 2014 #114

    TManiaci

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    Agreed, a pack in the range of 6S1P 3000 mAH 30C would be just right, and still give you the same flight times you have now if you used more of the capacity.

    If you are stuck with this airframe, the prop changes are in order. If swinging a bigger prop is out of the question, then a path to more power is to step up to a 7-Cell pack. That would increase power to the prop, and net around an addition 15% thrust on the 16x10. That's the max the motor can use, so the odd-ball battery pack type might be worthwhile. LiPo's are not that expensive any more. There is a Zippy 7S1P2700 mAH 35C pack (487 grams) for $42 now on HobbyKing. Good lightweight move with a power boost at the same time.

    Also consider a 16x12 and 16x14 prop, but they may be hard to find. There is a 15.5x12 4-blade... that could be your silver bullet. More pitch or more blades are your easy and cheap steps to more thrust. You are running that Motor-ESC combo well under it's capacity.

    So, there are a few thoughts to move this airframe to better performance. Do the 7S1P2700 pack and see what your amp load looks like. If it's still well under 65 amps, then step on prop selection too.
     
  15. Mar 5, 2014 #115

    Jace

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    Thanks for your guys time. I appreciate your feedback. And honestly (don't tell anyone) wheniI first started with this airframe it was glow.......... O.S. 61 swinging a 12x6 prop. So she is leaps ahead of what i started with. But getting closer to 6 lbs has gotta improve its flying.
     
  16. Mar 5, 2014 #116

    TManiaci

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    you're a dork :moon: HA!
     
  17. Mar 5, 2014 #117

    red7fifty

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    I"m shopping around for a suitable power system for a Sig King Kobra build.
    I'd like it to fly, similar to what a .60 size nitro would put out, meaning, an 11x7 ish prop turning 13,500 RPM, and fly they way these things were designed to be flown, under WOT for most of the flight.
    I have a bunch of 4S 2200 lipos, that, in an ideal world, would let me reuse, so I don't have to buy a 5s or 6s pack just to fly this, once in a while build.
    I've noticed, that most ".60" size electric outrunners, are calling for 5S and 6S batteries, and, have lower KV ratings and larger props, say 16's
    I'm pretty sure, I won't have that kind of ground clearance.
    So, the questions I'm trying to figure out, would a ".46" size motor be enough power if flown at WOT, using kinetic energy from a full throttle pass carried into verticals?
    As far as propping, I might either have to resort to, a smaller diameter prop in a 3 or 4 blade configuration to load these engines correctly, or, I considered an In-Runner with a higher KV.
    Would a 1000 KV in-runner be the ticket? At 14.4 Volt (4S), it would have a similar RPM to a .60 size nitro motor.....IF.....I could mount the same 11x7 or 12 inch prop. Or, another option???? Something in a 4000kv motor, turning a 4:1 gearbox, would also get the RPMs in the same range, but, would the prop size be correct?
    Doing all I can, to avoid having to buy a .60 size nitro engine......lol
     
  18. Mar 5, 2014 #118

    Jace

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  19. Mar 5, 2014 #119

    TManiaci

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    You have a lot of options. Using two of your 4S2200 mAH packs, paired in series wiring, will be a 8S pack. That will drive a 500kV motor 14,800 rpm no-load.

    You probably want a system that will make 1200-1400 watts to get the performance you want, but that pack will result in some short flight times. We can calc that when the motor is selected. You want 160-240 watts per lb (10-15 watts per ounce) for strong performance.

    The best match for that is an out-of-stock Turnigy Aerodrive SK3 - 5055-430kv Brushless Outrunner Motor at HobbyKing. That motor is 430 kV, so your no-load rpm is 430 x 8 x 3.7 V = 12,728 rpm. You would select a prop that would load that motor to about 50 amps. That would result in around 1200-1300 watts output (1300-1400 watts on the watt-meter). It should be in the 11-13 inch prop range.

    There are some Inrunner options that might work too.

    Flight time would be on the order of 5-6 minutes, assuming you ran moderate throttle, 3-4 minutes at full WOT is about all you would get.

    As you can see, when you step up for larger aircraft, it takes a lot more battery capacity. 2200 mAH is not a lot of capacity, and most aircraft in this class will run 3500 to 5000 mAH or more. You could double that, and wire four of your 2200 pack in a 2S2P configuration so you are basically running a 8S2P4400 mAH setup. That gets you up in the normal range of flight times over 8 minutes. Check the weight of four of those packs as a flight kit. If it makes sense, go for it. If you bird still can make a 7 lb-ish all up weight, that can work.
     
  20. Mar 5, 2014 #120

    red7fifty

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    Thank you, That is a LOT of helpful information, and takes some of the brain-ache out of the equation.
    Wiring up 2 packs into an 8S, would increase the speed, and get the prop diameter smaller too.
    The shorter flight times, 4 or 5 min, is fine, or, as you stated, double up with 4 packs, 2S-2P, into a a 4400mah, 8S combo.
    I am expecting the build to start in a week or twos' time........and once I get it framed up, and space figured out, I will start shopping for the motor and esc.
     

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