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extend flight times?

Old 02-05-2011, 11:52 PM
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Wrongway-Feldman
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So after much reading and headscratching I have but one question.
If one is happy with the performance of ones aircraft but wishes for longer flight times per charge, how does one go about it?
Is it as simple as increasing the Mah?
For instance if performance is fine with a 7.4 2S 1000Mah 15c, do I get longer flight times by simply going to a 7.4 2S 1500 Mah 15c?
Just about have the hang of electric, but this is still a stumper for me.
thanks.
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Old 02-06-2011, 12:08 AM
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Pretty much yes, the mAh capacity of your battery is like the gas tank size of your car, bigger gas tank means longer run time
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Old 02-06-2011, 12:14 AM
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Bomb Dropper
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But keep in mind that the bigger the battery, the more weight you add, thus reducing the performance of your motor/prop configuration due to having to haul a heavier load.
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Old 02-06-2011, 03:16 AM
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Wrongway-Feldman
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Thanks guys. That's the way I had it figured based on what I've been reading. What had me confused was a post by some-one who said they had a performance increase by increasing the Mah. Just didnt make sense to me.
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Old 02-06-2011, 03:29 AM
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Actually.. you CAN get a performance increase from increasing the mAh (capacity size). But there's a point where the weight of the bigger pack over-rules the performance gain you get from having more mAh. It's all about how many amps the battery can put out.

One way to get around that factor, is to buy Lipo packs with a higher "C rating".

Ex: 1500mAh 11.1V 20C Lipo ~vs~ 1500mAh 11.1V 30C Lipo

You will get more amps from the higher C rated battery pack.
Kind of like having 87 octane gas ~vs~ 93 octane gas.

Last edited by Bomb Dropper; 02-06-2011 at 05:10 AM.
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Old 02-06-2011, 04:58 AM
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kyleservicetech
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Originally Posted by Wrongway-Feldman View Post
So after much reading and headscratching I have but one question.
If one is happy with the performance of ones aircraft but wishes for longer flight times per charge, how does one go about it?
Is it as simple as increasing the Mah?
For instance if performance is fine with a 7.4 2S 1000Mah 15c, do I get longer flight times by simply going to a 7.4 2S 1500 Mah 15c?
Just about have the hang of electric, but this is still a stumper for me.
thanks.
Yup, providing a battery with more mah (Milliampere Hours) will add more flight time, plus more weight. And the battery weight pretty much goes up in direct proportion to the Mah rating. Would not be to hard to put in a battery that the model airplane can not get off of the ground.

And, if you're running a brush type motor, going to a brushless system alone will make a difference. Or, if you've got a brushless motor with poor efficiency, going to a higher quality motor will also help.

If your model is a slow flying type, and you've got a motor and prop with a high RPM, going to a brushless "Outrunner" type motor, with a larger diameter, slow turning prop will also make a difference. Check out the various Hacker A series motors. These motors are available in power ratings from several dozen watts to many Kilowatts. I've got 7 of them, ranging from an A30-12S motor to A40's, A50's and my new one is a A60-16M, running at 2400 watts (three horsepower)

Check out one of those PC spreadsheets, such as www.motocalc.com, that will allow you to put in your models specifications, motor specs, battery and ESC. This program is free for 30 days, then its $39, and IMHO, well worth it.
But this program is only as good as the data going in, and some of those very inexpensive imported brushless motors have poor accuracy on their specifications.
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Old 02-06-2011, 06:47 AM
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You can get a little increase in actual performance with a higher mah pack simply because the max allowable discharge (which is a result of the internal resistance of the pack), is a function of the C rating and the capacity. So a 1200mah 20C pack can tolerate a higher discharge (and potentially provide slightly more power) than a 1000mah 20C pack. Of course, the weight also goes up, so a better way to get greater performance is to simply buy a pack with a higher C rating, but the same mah rating. Roughly the same weight, but the lower internal resistance will provide a slight bump to performance.
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Old 02-07-2011, 04:57 AM
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Wrongway-Feldman
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Great info guys. Thanks alot.
I guess alternatively you could always pick up more batteries ( most of the ones I need are in the $5 to $8 range ) and swap em out more often at the field. Who couldn't use the landing practice? LOL
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