Battery life is too short - RC Groups
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Aug 02, 2012, 07:43 PM
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Help!

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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Aug 02, 2012, 07:48 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.
Aug 02, 2012, 07:54 PM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
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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Aug 02, 2012, 08:06 PM
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Evan D's Avatar
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...
Aug 02, 2012, 08:26 PM
ex-noob
Lardog's Avatar
Quote:
Originally Posted by jcalvert
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.
Aug 02, 2012, 08:29 PM
Registered User
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.
Aug 02, 2012, 10:10 PM
Registered User

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
Aug 02, 2012, 10:50 PM
Registered User
Ranandar's Avatar
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.
Aug 02, 2012, 11:23 PM
Wake up, feel pulse, be happy!
Piece's Avatar
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.
Aug 02, 2012, 11:39 PM
Registered User
scirocco's Avatar
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.
Aug 02, 2012, 11:56 PM
Registered User
Quote:
Originally Posted by scirocco
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...)
Aug 03, 2012, 12:13 AM
Registered User
scirocco's Avatar
Quote:
Originally Posted by rafe_b
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.
Aug 03, 2012, 07:17 AM
Wanted for breaking Ohm's Law
Dennis Sumner's Avatar
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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Aug 03, 2012, 11:15 AM
Registered User

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
Aug 03, 2012, 01:19 PM
Electric Coolhunter
Thomas B's Avatar
Quote:
Originally Posted by jcalvert
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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