Thank you!
Ok thanks but I do not have these tools. I have a drill only. What is the 1.3433 number and how do I get the volt (6.44) number? I think I can get RPMs in the Focbox with Real-time tool but what about the other numbers?
That’s ac volts measured at 1880 rpm.
KV is an inherent constant of a motor, right? So you can solve for X (kv) if you know the other variables.
I rogered up to measure them RC plane style largely bc I had intended to do for months.
Yes, you can pretty much feel the difference between a 150, 190, 220 kv motors.
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where? using the wizard, or the motor foc page? or where?
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If you have the ERPM measurement from VESC Tool already you can calulate the KV just by
ERPM / “duty cycle” (0.95) / “polepairs” (usually 7) / “volts” (you can use the VESC Tool reading) = KV
This for sure is also not 100% acurate becuase ERPM flactuates a bit, the voltage reading may be a bit of and the supply has to be stable but that’s what worked for me so far.
straight Kv calculation from the VESC tool terminal never worked for me but just spin it max erpm and in the lower left you see the value, then you have voltage, poles numbers and you calculate Kv. Super simple.
I could be wrong but I think the kV calculation in VESC tool only works in BLDC mode.
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Hope this answers your question 
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Thanks. I’ve seen numerous ways now.
i’m still wondering how/when the kv command in the terminal of vesc tool works.
and @Soflo’s comment made it sound like it was also just displayed in the normal vesc tool windows somewhere.
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It measures ERPMs. So I have 56k ERPMs and 47 V in.
So… 56,000 x .95 = 53,200 / 7 = 7,600 / 47 = 161.7 (170KV???)
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this is eggzakery how I do a sanity check on my motor(s) Kv!!!
In a pinch when I don’t have my optical tach I fully charge the drill and use the MFR rpm (yeah I know) or a drill press with a known RPM…
It’s been useful enough for me…!!!
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Yup, sounds right. (I always figure +/- 10% for this kind of reading.)
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So Mike and I figured it out. We took 2 motors. One was definitely a 220KV motor. And tested RPMs and Volts. Wrote down the info. Then tested the unknown motor. The readings were almost identical. Both motors are 220kv
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FYI this didn’t work for us. We used the drill / rpm / volt method and we nailed it.
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That’s pretty much what we did and it worked!
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They are 220, yes. So you can’t just run ERPMs to calculate the motor KV. Comparing it to a known motor using a drill to calculate RPMs and Volts worked out. Theory proven that ERPMs can’t be relied on because I have another board with 190s and the ERPMs are exactly the same.
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possible that maybe why never worked for me 
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Do you know of a way to calculate how many RPMs by knowing they are 56,000 ERPMs?
Convert ERPM to RPM?
Count the magnets inside the can by observing the lines of brake dust that stick to the outside of it. Divide that by 2 to get the number of pole pairs. Divide the erpm by the number of pole pairs to get the rpm.
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