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Brushless motor voltage

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Brushless motor voltage

Old 05-22-2020, 06:18 AM
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Default Brushless motor voltage

Let's suppose I have a brushless motor rated to run on max 3s lipo (11.1v) and 100A current. When running the same motor on a 2s lipo, would the maximum current the motor could consume be reduced as well, due to V=IR?
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Old 05-23-2020, 06:30 AM
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Originally Posted by BoredGuy View Post
Let's suppose I have a brushless motor rated to run on max 3s lipo (11.1v) and 100A current. When running the same motor on a 2s lipo, would the maximum current the motor could consume be reduced as well, due to V=IR?

Generally a motor will be relatively fixed on how much power it will draw measured in Watts where using Ohm's Law --> Watts = Volts x Amps


Unfortunately some motors will draw more power if you increase voltage so that makes things a little more tricky, but let's just assume that we have selected a motor that draws the same fixed power "500W" for example. Then note the ESC controls how much voltage is applied through the speed control where the following example is with the ESC at max throttle in both calculations with fully charged LiPo's:


2S LiPo:

500W = 8.4V x A or A = 500W/8.4V = 60A in order to get the full 500W of work out of the motor


3S LiPo:

500W = 12.6V x A or A = 500W/12.6V = 40A


So in order to pull the "same amount of power", you will see that increased voltage draws 1/3 less current which is significantly more efficient.


Things start to get more complicated in reality because many motors will not pull the max rated power at lower voltage which is why you will get increased speed as you draw more power (watts) with higher voltage. So when you increase power (watts), then yes you will increase current (amps), but it will not typically increase the current (amps) any more than when you were running it at the lower voltage. Hope this helps your understanding better.


Try to think in terms of Power being increased instead of Current when you increase voltage.
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Old 05-23-2020, 07:12 AM
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A more apples to apples comparison would be comparing 2 motors from the same manufacturer with identical can size and rotors:

2S @ 4500KV
3S @ 3000KV

both setups will yield identical performance with each motor pulling the same amount of power, but the 3S configuration will pull less current and run more efficiently and will offer longer run time if both setups had identical battery capacity in watt-hours

It all comes down to selecting the proper KV motor for the desired cell count battery you plan to run
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