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I have a BLDC motor, and I have an ESC to control it. These 2 are commonly bought together on Amazon.

The ESC is rated at 50 Amps continuous with a max current of 150 Amps. I am confused how this BLDC motor doesn't constantly exceed the 50 amp rating.

The BLDC motor is rated at 2900W and can be run from 18 - 42V. If I am going to run the motor with a 36V battery (building an electric skateboard) then the amperage would be 2900W / 36V = 80A when I have the throttle held all the way down. I like traveling at high speeds so most likely I will have the throttle held down all the way for most the ride.

Does this mean I need a higher rated ESC? Or is this fine?

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    \$\begingroup\$ please supply datasheets for both devices \$\endgroup\$
    – jsotola
    Jun 3 at 22:55
  • \$\begingroup\$ Motor is probably only rated 2900W at 42V which will give you a current rating. Reducing the voltage doesn't allow you to increase the current. Then read the (possibly non-existent) fine print. It may well be continuous rated at a lower current still. \$\endgroup\$ Jun 3 at 23:03
  • \$\begingroup\$ It's like highway driving. Once you get up to speed, you tend to stay moving and you only need to overcome friction and drag. Unless going uphill. But you still probably shouldn't be going full throttle the entire time. And what the guy above said, max current doesn't scale. \$\endgroup\$
    – DKNguyen
    Jun 4 at 0:04

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The eBay listing says "The Max Output Watt is 2900W". They probably mean input power at 42 V. The listing also says "Not Easy to Get Hot" which probably means it will burn up if run at 2900 W continuously.

Your ESC is rated for 50 A continuous, 150 A 'instantaneous'. That means it should be able to deliver 36 x 50 = 1800 W continuously, and 150 x 36 = 5400 W momentarily.

The more load you put on the motor the more current it will draw. Use an appropriate gear ratio to keep the continuous current below 50 A and it should be OK. If this doesn't provide enough speed then you will need a higher rated ESC.

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