Is there a way to meassure motor KV?

ESK8 Electronics
1

According to the Electric Skateboard Calculator the final speed on my Vanguard build on @Torqueboards 190KV motors is spot on, extremely precise, but on my Reaper with 190KV motors from Polar my speed is off by 5km/hr.

I wonder if there is a way to meassure KV directly on the motors to see if Polar motors are in fact 170KV or 190KV as I thought from the begining.

Loaded Vanguard

image.png592×772 202 KB
Screenshot_20170424-215737.png1440×2560 311 KB

Never Summer Reaper

image.png609×768 204 KB
Screenshot_20170424-215655.png1440×2560 310 KB

If I change the motor to 170KV the speed matches the skateboard calculator perfectly.

image.png582×770 208 KB

2

The motor constant (Kv) is measured without a load. There are expected losses in power.

3

Both speeds were meassured on the bench, so both e-boards are subjected to the same loses, however the Vanguard matched the speed and the Reaper not.

4

In the bldc tool, after you have ran the motor, go in the terminal and type “kv”

You will get the kv in erpm, divide that number by 7

3 Likes