Hey

I have motor, but I don't know the kv. The writing is erased

Is there a way to know the kv?

It's probably possible to make a guess from stator size and testing thrust, but it's a really good question. Someone will probably know.

BTW, are you writing a book on FPV? You ask a lot of disjointed questions that would ideally be suited in a FAQ.

(10-Apr-2024, 12:46 AM)Eyes.fpv Wrote: Hey

I have motor, but I don't know the kv.  The writing is erased

Is there a way to know the kv?

kV is RPM per volt without load. Yes you can find the kV by measuring yourself. However you do need some equipment. What I used to do was to make a light weight disk and paint it half white and half black. Then I use a DC power supply with voltage readout. I then output an even number like 10V and measure the RPM with an optical tachometer. Then I increase the voltage to 20V and test some more. Do 5 to 10 tests for each voltage and write down the RPM. Then take an average. Use the RPM from 10V and divide by 10. Then take the RPM from 20V and divide by 20. By the time you finish with all the tests you will have a very good idea what is the kV of your motor. Better than the number from the vendor.

Post an image of your motor, we might know it maybe.

(10-Apr-2024, 02:33 AM)Pathfinder075 Wrote: It's probably possible to make a guess from stator size and testing thrust, but it's a really good question. Someone will probably know.

BTW, are you writing a book on FPV? You ask a lot of disjointed questions that would ideally be suited in a FAQ.

Sorry for asking so many questions, but my problem is that questions come to my mind and I try to answer them, and I share them here, perhaps someone will benefit.

(10-Apr-2024, 03:01 AM)SeismicCWave Wrote: kV is RPM per volt without load. Yes you can find the kV by measuring yourself. However you do need some equipment. What I used to do was to make a light weight disk and paint it half white and half black. Then I use a DC power supply with voltage readout. I then output an even number like 10V and measure the RPM with an optical tachometer. Then I increase the voltage to 20V and test some more. Do 5 to 10 tests for each voltage and write down the RPM. Then take an average. Use the RPM from 10V and divide by 10. Then take the RPM from 20V and divide by 20. By the time you finish with all the tests you will have a very good idea what is the kV of your motor. Better than the number from the vendor.

Is there a way in Betaflight to increase the RPM of the motor in the motor tab?

(10-Apr-2024, 09:41 AM)Eyes.fpv Wrote: Is there a way in Betaflight to increase the RPM of the motor in the motor tab?

Not sure about your logic here. RPM of a motor is a function of battery voltage and throttle position. BetaFlight is a configurator that configure your flight controller. I am not sure why BetaFlight can increase or decrease the RPM of your motor. Unless of course you have the wrong firmware on your speed controller. Back in the old days we have to calibrate the speed controllers by powering up with the throttle stick at the highest position. That seemed to have gone away with the newer setups. However those are all about hardware and firmware and not so much about BetaFlight.

There is bo image attached, use igmur and post the link as example

(10-Apr-2024, 08:57 PM)hugnosed_bat Wrote: There is bo image attached, use igmur and post the link as example

https://imgur.com/a/W4oVWSg

(10-Apr-2024, 09:41 AM)Eyes.fpv Wrote: Is there a way in Betaflight to increase the RPM of the motor in the motor tab?

Hi Eyes,

There is no way to increase the motor KV as that is maximum. 
However, you can decrease the functional KV by putting a limit on the
the motor output. While this is not as good as buying lower KV motors,
it doe allow use of a higher voltage battery.

Later, iFly 

(11-Apr-2024, 11:36 AM)Eyes.fpv Wrote: https://imgur.com/a/W4oVWSg

Looks to be a XING motor but as fitted to iFlight Nazgul, etc. They were unmarked.

They did this for 4S (roughly 2300kV) AND for 6S (roughly 1900kV) and the windings, colour, etc, looked the same (I have both) and if so, no-one will be able to state accurately