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Old Aug 02, 2012, 06:43 PM
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Battery life is too short

I am running into a very short flight time problem, any suggestions appreciated.

1) I am flying a Parkzone T-28 Trojan
2) non-stock motor: Turnigy G10 1100 (the performance is great )
3) 2200 mAh 3cell 30c battery. I use six different ones and they all last the same time. So it is not a bad battery per se.
4) I get about 5 minutes of flying at about 80% throttle leaving battery voltage at about 3.7 volts per cell.
5) I am using a Turnigy Plush 40 amp speed controller.
6) I am using an APC 10 x 7E prop.

So, what gives. Can I change something to increase the flight time.
Thanks
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Old Aug 02, 2012, 06:48 PM
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Its either the motor or the prop. I've heard those Turnigy "G" motors are pretty inefficient fight time wise.
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Old Aug 02, 2012, 06:54 PM
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I have a Turnigy G10/1100 and I am getting 8 minute flights but using a bit smaller prop 9x7 1/2 and a 3S2650. Mine is in a Top Dawg and really scoots....Overall I think the Turnigy Easymatch motors are a pretty good bang for the buck, their specs are the same as E-Flite motors....

Do you have a Wattmeter? And have you tried using a smaller prop? (10x5, 9x6, or 9x7 1/2)
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Old Aug 02, 2012, 07:06 PM
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There you have it, larger prop and smaller battery is 5 minutes. Smaller prop and larger battery is 8 minutes. Get a bigger battery. But the down side is that you will have a higher weight and the plane will feel sluggish...
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Old Aug 02, 2012, 07:26 PM
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Quote:
Originally Posted by jcalvert View Post
So, what gives. Can I change something to increase the flight time.
Thanks
Yes, a few things...
  1. Back off the throttle a bit and don't fly near WOT the whole time.
  2. Use a larger capacity pack, like a 2650 or even 3000mAh.
  3. Use a smaller prop that doesn't draw as many amps.

Of course, flight characteristics will be different with all these so be prepared accordingly.
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Old Aug 02, 2012, 07:29 PM
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On what basis do you claim battery life is too short? Have you measured the actual power or current, either statically or in flight? Offhand the parameters you list seem mostly reasonable -- ie., motor Kv, motor & prop size, battery, etc. 5 minutes at 80% throttle seems maybe a little low, but not outrageously so.
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Old Aug 02, 2012, 09:10 PM
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Battery life is too short

Thanks for all the replies.

I notice that no one has mentioned the ESC timing parameter.
Mine is set on Medium. Is that correct?
Thanks
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Old Aug 02, 2012, 09:50 PM
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If your ESC timing is off the motor will howl at high throttle.
Try the smaller prop, a cheap easy fix first.
A balanced prop is more efficient too.
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Old Aug 02, 2012, 10:23 PM
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Five minutes of flight time leaving the pack at 3.7V per cell (~20% capacity) equates to an average draw of about 21A. If you're flying that setup at 80% throttle continuously, I'd say that five minutes is exactly what I'd expect to see.

You either need to fly with less throttle, get a pack with more capacity, reduce prop size, or get a motor that's more efficient (power out vs power in). Or all of these.
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Old Aug 02, 2012, 10:39 PM
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One last thing, and I accept it would be hard not to notice with an APC prop, but the prop's not on backwards??? Some models will fly surprisingly well with the prop backwards, but it sure wreaks havoc with prop efficiency and thus performance and flight time.
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Old Aug 02, 2012, 10:56 PM
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One last thing, and I accept it would be hard not to notice with an APC prop, but the prop's not on backwards??? Some models will fly surprisingly well with the prop backwards, but it sure wreaks havoc with prop efficiency and thus performance and flight time.
I think the effect would be drastic, and would be noticed as a severe impairment of the model's performance. (A lesson I learned the hard way, early on...)
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Old Aug 02, 2012, 11:13 PM
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Originally Posted by rafe_b View Post
I think the effect would be drastic, and would be noticed as a severe impairment of the model's performance. (A lesson I learned the hard way, early on...)
Only asked because I did the same thing recently, tho not with an APC. Impaired, yes a lot; drastic, unflyable, surprisingly no. The cue was flying around at 80-100% throttle when I expected to be using nearer half.
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Old Aug 03, 2012, 06:17 AM
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I think the one key thing is to find someone with a wattmeter and check your setup. The G10 max current is 32 amps. I checked my Top Dawg setup and with a 9x7 1/2 APC and a 3S2650 Sky Lipo I measure 28 amps.

I hope that helps.

Denny
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Old Aug 03, 2012, 10:15 AM
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battery life too short

Thanks for all the replies.

No, the prop is not on backwards. I did that once and it produced a very noticeable swishing noise at full power.

A 9.5 x 7.5 prop did not help this morning. So I guess bigger packs are the best answer.

Cheers
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Old Aug 03, 2012, 12:19 PM
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Quote:
Originally Posted by jcalvert View Post
Thanks for all the replies.

No, the prop is not on backwards. I did that once and it produced a very noticeable swishing noise at full power.

A 9.5 x 7.5 prop did not help this morning. So I guess bigger packs are the best answer.

Cheers
A 9.5x7.5 is going to have about the same draw as the 10x7...you did not really prop down any amount to speak of. Try a 9x7 or a 10x6.
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