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Old Jul 29, 2011, 07:33 PM
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Mexico, BC, Mexicali
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Quote:
Originally Posted by manuel v View Post
Never use this set up guide.
http://www.rc-electric-jets.com/Elec...uidelines.html

Manuel V.
To calculate your fan rpm’s:

Take the voltaje of the battery and multiply the Kv of the motor = fan RPM.
11.1V x 3600= 39,960.

A reality more about:

3 cell lipo, have a voltage of approximately 12.6Volts.
The new batteries 30 and 20 C 40C sustain discharge voltage 11V average. (Use the voltage rating is very rough and correct)

A very important factor that is missing from this equation is the NLS% (percentage of No Load Speed.)
In EDF is very important that the engine is not charged too much for this factor does not drop below 80%. Possibly in some applications where the motor is much torture can be used up to 75%. But it is highly not recommended.

Also consider the actual motor Kv can vary the die post for the manufacturer.


Take the voltaje of the battery and multiply the Kv of the motor and multiply for %NLS factor = fan RPM.
11.1V x 3600 x 80%= 31,968 RPM.


To Calculate what Kv motor you need:
Take the desired fan RPM, divide it by the battery voltaje = Need ed motor Kv.

45,000 / 14.8 = 3,040 kv.

As in the example above to factor% NLS,

45,000/14.8=3040*100/80= 3800 Kv.

To Calculate what battery you need:
Take desired fan RPM , divide by the motor Kv, = Battery size.
45,000 / 3600=12.5Volts (3cell)


Once you factor% but the NLS was ignored the formula would be:
45,000 / (3600 * 80%) = 15.62V (can not say they are 4 cell)
It is impossible to change the voltages of the Lipo. Will always be multiples of 3.7.
So we have to recalculate to 4 or 5 cells. To calculate the Kv busy, since it is the only viable option we have, change the engine to the appropriate one.

45000/14.8 = 3040 * 100/80 = 3800Kv.
Using 4 cells occupy a Kv of 3800.

45000/18.5 = 2432 * / 80 = 3040Kv.

Using 5 cells occupy a Kv of 3040.
After all this formula is the same as the previous one and is virtually unnecessary.


For convenience we use an Excel for these calculations.

Manuel V.
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Last edited by manuel v; Oct 20, 2012 at 12:42 AM.
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