How to match esc to motor - RC Groups
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Oct 28, 2007, 04:04 AM
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How to match esc to motor

I'm new to this site and new to rc modeling, I was hoping you all could answer a question for me.
I'm assembling my second plane, an E-Flite mini showtime. I bought the 480 motor for it and the guy at the hobby shop recomended a 25 amp ESC. Reading more on my own I've seen a 40 amp ESC recommended. (I'm going to use an 11x7 prop.) My question is will this 25 amp work? Am I risking damaging the motor? Would the 40 amp be better? What factors determine which ESC for a given motor?
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Oct 28, 2007, 04:40 AM
Registered User
Welcome to the forum

First thing, using a larger ESC than necessary will not harm the motor. It will cost more, and weigh more, but will probably run cooler and may also have a larger BEC in it (the Battery Eliminator Circuit, which supplies 5v for your receiver).

Obviously, you have to get a brushless ESC for a brushless motor, or a brushed ESC for a brushed motor. They cannot be mixed. Then you normally choose an ESC which is rated for a bit more current than the motor is rated for. I usually go for 15% to 25% more than the motor rating -- maybe more if my ESC is going to be placed where it won't get good cooling.

I can't see the amps rating for the eflight 480, but they rate it at 275 watts which would be 25 amps with a 3S LiPo (watts = volts x amps). So, in my opinion, a 25A ESC is too small -- I personally would go for 30 amps or more.

I can't comment on the suitability of the 11x7 prop because I'm not familiar with that motor. But you are aware, aren't you, that all else being equal it's the prop size that determines how many amps the motor is going to draw? So ideally you need to be able to measure the actual current whenever you try a new motor/prop combo so that you can be sure it's not overloading the motor. Most people here use a wattmeter like the ones here

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