E-Flight Power Sources Ask questions or read about power sources as they specifically relate to e-flight including Lithium-ion, Li-Poly, Nimh and Nicad battery packs.

KV rating ?

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Old 12-19-2014, 10:02 PM
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Ed
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Default KV rating ?

Yes, I'm a newbie, and I'm trying to understand what KV means ? I don't think that it means Kilo Volts in our case. Why and how is it important to know the KV rating of a motor ? For example: I have a Turnigy 42 that has 500 KV printed on the side. What would this motor be good for ? Speed, or endurance ? How does a 500 KV compare to a 1000 KV motor ? Which one draws the most current ? Which one is the better performer ? Does one turn up more RPM's then the other ?


I'd really appreciate knowing as much as possible about KV. Can anyone help ?


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Old 12-20-2014, 06:03 AM
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Kv is RPM (in 1,000s) per volt, so all other things being equal, a motor with a higher Kv rating will try to spin the prop faster. In general, you can think of this like a higher gear in your car, a higher Kv is better for higher speeds. BUT you really need to look at the entire system in order to make any kind of assessment (Kv by itself is meaningless without knowing what battery voltage/current capacity and prop diameter/pitch).

Try playing around with some of the on-line calculators to get a sense of how the various components interact:

Webocalc: http://flbeagle.rchomepage.com/softw..._imperial.html
eCalc: http://www.ecalc.ch/motorcalc.php?ecalc&lang=en
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Old 02-27-2015, 02:43 PM
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The KV rating is just part of the puzzle.
1. Picking a battery voltage
The size/power of the motor and the desired propeller has a great deal to do with the RPM.
Most propellers that I use are most efficient when they have a 6.5 pitch, and twelve to thirteen inch lengths.
Desired RPM - - I start out with about 10,000 RPM as a first wag. I prefer a final range between 9 and about 13 thousand RPM
Lower diameter propellers can be used at higher RPM than larger ones.
Motors power My models range from about 500W to more than 1,600W
Batteries used usually 4S and 6S for the 1600W motor.
E Calc (propeller) can be accessed via the castle creations web site or directly. The Castle link will usually give access to a better motor selection.
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