What does "Kv" mean on brushess motors? Kv explained!

Ever wonder what "kV" actually means and how it relates to the operation of your brushless motor?
Link to video mentioned in this video about KV and motor temps/gearing: • Brushless motor temps,...
SkyRC Motor Analyzer: www.rcjuice.com/skyrc-brushle...
Questions? Contact us: www.rcjuice.com/contacts/

[@89rc_dude33]

Just what i was looking for. Thanks. Staying for longer.

[@jasonranaweera3630]

Thank you so so much for this lesson sir! I just really found this useful. Keep up the good work!

[@Mark-ro5zg]

Thanks for the info. Surprising how quite the brushless motor is compared to the brushed.

[@shantanu83]

Thanks for explaining this so easily!

I loved your explanation. Thanks.

[@TheMrTJOX]

The K in the Konstantin comes from the German spelling of constant (konstant). They changed the spelling to English, but kept the original K.

[@inhimwelive3951]

Can you possibly provide a link for the delusional soys. thanks

[@TheMrTJOX]

@@inhimwelive3951 Of they were in STEM, they'd know. Too much technology for me to have to direct people... folks that NEED to know will find it. Others will remain where they are "WOKE", but not awake!

[@inhimwelive3951]

@@TheMrTJOX My apologies, I did not know I was dealing with a stupendous Steward of said subject. Finish your rant. And if not, be well.

[@TheMrTJOX]

@@inhimwelive3951 how can someone be a steward (spellchecker is free) of public information???

[@inhimwelive3951]

@@TheMrTJOX Thanks for that,since you are so educated, can tou define a woman?

[@CPB24421]

That was great.. really enjoyed that video. Thanks

[@paultro8457]

You guys are my go to battery for all my RC's. Always had good luck with your products and I like that you have weekly sales. Anyway, thank you very much for explaining all this. I'm headed to watch the other video right now.🤙

[@RCJuice]

Thank you for taking the time to comment and for your business Paul, we appreciate it!

[@martinbullla7654]

​@@RCJuiceI have a hobbywing Max 6 I put it in my Sledge and that's got a 2000 KV motor in it is it okay to run it I mean the caps on the ESC get a little hot but not too bad and it never went into shut down so you think it'll be fine my stock one died they sent me a new one but now I don't want to take the hobbywing out because it has so much more power and it's only on punch setting one and it will pull the wheels off the ground while it's at like 30 miles an hour 40 miles an hour it will pull the wheels if I punch it

[@RCJuice]

@@martinbullla7654 As long as temps stay in check then yes, it's oK to run.

[@dorianshepard2841]

I wish hard info channels like this were easier to find

[@Maurice1151]

Good explanation. Thank you.

[@joeleames1151]

Amazing video - answered a lot of questions I had. You talked about the number of turns as a representation of how fast brushed motors were (back in the day). The wire winds are around the armature instead of the stator. I'm actually amazed that brushed motors are still around considering how superior brushless are.

[@RCJuice]

In RC they are really only still around for the crawler guys (still tough to get a brushless motor as smooth as a brushed motor in the slow speed stuff) and for the ultra-budget cars.

[@samuelandolina6338]

Great video!!

[@skimnekgaming]

Great info! Thanks

[@tyshiddejuremanbey1313]

OUTSTANDING!!!

[@ndrsg3013]

Thank you explained very well, clear and simple... Here a summary of what you mentioned: Kv is equal to 100 RPM per volt Note: Higher Kv losses torque. Higher Kv motor runs motor faster Higher Kv heats the motor faster

[@RCJuice]

Thank you for watching! KV is fixed, and the RPM is (KV x Voltage).

[@guypehaim1080]

It seems the Kv is written reversed. In math, we normally put the modifier after the name as a subtext: Vk.

[@aidenmaves5537]

Thanks

[@michaelhoffacker3162]

Thank you, I thought it was kilovolts! Excellent explanation I know how to up my gear to motor power ratio

[@sewingmachinesindetail]

Thanks for this video. Depending of the software in the ESC, it could do SpaceVector PWM with a 1.15 times higher voltage than Sinosoidal PWM. What kind of ESC will the motor manufacturer presume, when they define the KV value?

[@ebenwaterman5858]

Technically, the old "turns" spec. hails from DC motor days. Probably slot cars. It was used to simplify the motor specs for comparison purposes. With DC motors the speed is limited by the back EMF the winding's generate when it is rotating. If a 10 turn DC motor is spun (as a generator) at say 1000 rpm and generates 1 volt, then 1 volt will only be able to spin it a 1000 rpm. If you wind it with 9 turns, it will only generate .9 volts. But, if you power it with 1 volt it will spin at 1111 rpm. This is where slot car racers got their speed advantage because you couldn't raise the voltage. This back EMF problem still exists with brushless motors. I think. :)

[@T_B_O_A_Chainbreaker_M]

If I have a motor 7700 KV with a ESC 120a: what’s the best battery to get for it including discharge rate?

[@Ghost-un4fu]

I have a question I just started in the rc car I’m working on building a drag race car, how can I get the car to be quick off the and fast. I’m useing the black slash body the spektrum esc and 4000kv motor

[@NCMATT]

New sub

[@hondayamaha3]

thanks for the explanation, I'm finding what is the right motor for rc boat. heating is not a problem since I have water cooling and propeller put less stress than car gears I assume. to higher kv it is. thanks alot

[@RCJuice]

True, boat motors do have the benefit of water cooling but also lack airflow so there is a trade-off. Prop pitch can affect operating temps the same as gearing in a car so it's still important to monitor those temps.

[@hondayamaha3]

@@RCJuice thanks

[@m.a.s.hq8715]

Thank u man i have hobbywing 1800 kv on my axial scx10 , just planning to upgrade to 2800kv but my concern was the torque, but after watching ur video i'm gona stick with my 1800 cuz i don't want to lose torque specially while crawling

[@RCJuice]

Thank you for watching!

[@m.a.s.hq8715]

@@RCJuice hi juice , is it worth to upgrade to hw 2300 kv pro , and what do u know about this motor? thanks

[@RCJuice]

@@m.a.s.hq8715 Not sure which motor in specific you are asking about, but please feel free to email us at [e-mail] and we can help further.

[@m.a.s.hq8715]

@@RCJuice i have hobbywing 1800kv combo , but i'm planing to upgrade to hobbywing 2300kv pro .. so is it worth to upgarde ??

[@BananaBabys]

@@m.a.s.hq8715 I have the 2300 kv fusion pro and I feel that it is overkill for my scale tf2 crawler. Way too fast and I stripped the ring and pinion gears. I am downgrading to a cheaper less powerful motor. Probably the fusion se. The pro might be better on a stronger platform like the trx4. On rc4wd stuff it needs to be babied like a real truck. Also the slow crawl is very nice on the pro. Even with big tires I can get ridiculously slow and still torquey. Just overkill on both sides ends, slow torque and top end.

[@mangosouljah]

Hey, great video and very informative However I am still not sure about my soon to be setup Battery: 3s 2300mah 120c ESC: 120a hobbywing rated for 2-4s Motor: 2845 4300kv Will the motor bottleneck and or not handle the rest of the setup?

[@modelaircraft6576]

The bigger the model, the lower kv will be suited for that particular application. The smaller the model the higher kv you want for that particular application. If the model is small an install lower kv motor it will mess up cg and it won’t be any faster.

[@apostolis3255]

Which application? Can you please explain? My English isn't good and this video didn't have subtitles..

[@wvlfkvnt]

You’re not accounting for CAN size. A 1412-3200kv and 1415-3200kv are completely different rigs.

[@neilhabermehl6187]

The RPM of a 3 phase motor is determined by the number of poles and the frequency (Hz) of the AC. The displayed voltage did not change yet the RPM changed as you rotated the knob on the motor analyzer, so clearly RPM is not a constant with respect to input voltage. What is the frequency range that the motor analyzer changes over as the speed control knob is turned?

[@GhostYT_lat]

The displayed voltage is the input voltage not what's going to the motor.

[@aaronzdanz]

Hi Lawrence - thanks for this video! I'm a dunce when it comes to this stuff. Are you saying (from the comments below) that it doesn't matter how many volts your battery delivers? That seems so counter intuitive to me.

[@RCJuice]

It does not matter in the sense that your motor will run on it, but if your voltage is too low for the given KV the motor will be slow/lack power, and if the volts are too high for the given KV you can burn up the motor, and in some cases the ESC/battery if the overheating is excessive.

[@carscoffee5263]

Can you change the kv in a brushless motor?

[@RCJuice]

N, the KV is determined by the windings so you would need to re-wind the motor.

[@RCPlaneNut]

Yes I need help still I have this motor 3658-1920Kv inrunner motor with 9-blade 80mm fan and want to know if I can use a 130 amp Spektrum smart esc with this system

[@RCJuice]

It should be OK, but again, it depends on the voltage you are running and the actual load on the motor which determines the amperage being pulled. If you are exceeding the limits of the ESC on that motor then the motor would likely overheat though, the ESC should be fine if set up properly.

[@RCPlaneNut]

@@RCJuice it’s on a 6s battery

[@RCJuice]

@@RCPlaneNut Check the motor temps, but from the specs that sounds like a good setup.

[@idaayudayangiswari4272]

Hi can i ask?, i have 3300kv motor what battery should i use should i use the 3s 11.1v one?

[@RCJuice]

3S is high for 3300KV, it can be done if you closely monitor temps, it will be a powerful/fast setup but likely prone to overheating.

[@kaljsdlksjfd3286]

What about the load it can handle?

[@elektron2kim666]

K in constant and control is quite European.

[@bankstube9290]

Thanks for the video. Lets put a K in the front to screw everyone up

[@acdfus]

What motor would be best for carpet track racing?

[@RCJuice]

Depends on the specific car, but the majority will use a 540 brushless sensored motor like: www.rcjuice.com/motor-esc/brushless-car-motors/1-10-motors/hobbystar/hobbystar-540-pro-v2-competition-brushless-sensored-motor.html

[@acdfus]

@@RCJuice It is a Calandra Racing Concepts Battle Ax 3.0

[@RCJuice]

@@acdfus We'd recommend the HobbyStar 540 V2 motor for that car: www.rcjuice.com/motor-esc/brushless-car-motors/1-10-motors/hobbystar/hobbystar-540-pro-v2-competition-brushless-sensored-motor.html

[@acdfus]

@@RCJuice Thanks for your help

[@FeraAlfian-vu1wy]

I have a wltoys 124007 with 4300kv motor, I need a second motor with 1-2k kv for torque, any recommendation? btw thanks for your explanation it helps a lot :)

[@RCJuice]

Very tough to find small motors with low KV's, you typically only get below 1500KV on 1/8 motors and larger.

[@FeraAlfian-vu1wy]

@@RCJuice thanks for the reply, do you think 3100kv enough to load 110mm wheels?

[@RCJuice]

@@FeraAlfian-vu1wy It should be OK, just make sure to monitor motor temps and adjust gearing as you'll probably have to gear down a good amount if the wheels are a good amount larger than stock.,

[@FeraAlfian-vu1wy]

@@RCJuice tyvm it helps a lot!

[@abdulaziza]

Does KV change with load on the motor?

[@RCJuice]

No, the KV rating of a motor is determined by the physical stator windings and therefore does not change.

[@hanswallner2188]

great content, thank you! (but baaaaad audio quality, please change mic or position of mic, or do anything to reduce unwanted nasty reverb)

[@F4h4d1]

Would a 1200kv have more torque than a 2400kv motor? Is it better run a 1200kv on a super heavy Truck?

[@RCJuice]

Yes it does. When possible, it is always better to run a lower KV and more voltage, it's a more efficient and cooler running setup.

[@F4h4d1]

@@RCJuice Gotcha. Thank you!

[@cadeblain2265]

Is a 17.5 size motor the same as a 550 sized motor ??

[@RCJuice]

17.5 is a winding/KV rating and does not denote size, 550 is the size of a motor.

[@zrebrutibreniti]

how about current? does it affect the rpm too? sorry dummie here

[@RCJuice]

Current doesn't directly affect RPM, the motor is going to pull the current it needs for the given load.

[@earlshephard8879]

Esc

[@nickwilliams6869]

If i want to upgrade motors do i upgrade the car battery

[@RCJuice]

Not necessarily, it depends on the KV of the motor and the existing battery voltage.

[@nickwilliams6869]

@@RCJuice i want to upgrade the battery and the motor is 550 brushed

[@martingh4669]

Where I can contact you?

[@RCJuice]

www.rcjuice.com/contacts/

[@Positive_Altitude]

Well, there are 2 big problems with this video. 1) Kv is the "velocity constant" or "back EMF constant" a term straight from the motor theory, not "constant voltage" 2) measuring Kv this way is wrong, that shows of misunderstanding of what Kv actually is. Yes, Kv shows a relation between RPM and volts. But it is back EMF volts, not battery volts. In your case, you have current flowing through the motor, so there is a voltage drop because of the winding resistance, so BEMF is actually lower than your battery voltage. To properly measure Kv you need to spin the motor with another motor and measure the peak phase voltage. That will be your BEMF voltage because there is no current flowing in this case. And now you can divide RPMs by BEMF voltage and get the proper Kv value.

[@jamesjackson4224]

So my reedy 9600kv on my rc18mt is cranking out 120000rpm at 12.6 volt? 🤤

[@RCJuice]

It will certainly try, but you will either physically explode the rotor at that RPM or quickly melt down the motor and could damage the ESC/battery as well.

[@jamesjackson4224]

@@RCJuice so far so good I've ran it quite a bit without issues. It hauls

[@blankabison1331]

rpms per volt is what it really means

[@Blueknight1960]

I have a leopard 58113 v2 870kv motor. Now if you do the math like you said, 870kv x 33.6v = 29,232 rpm, but yet the motor spins at 45,000+ at full throttle.

[@RCJuice]

Have you checked the motor KV with a motor checker? Are you measuring the voltage at the motor when testing?

[@Blueknight1960]

@@RCJuice Actually it was the castle esc logs which stated the rpm's.

[@RCJuice]

@@Blueknight1960 We don' thave experience with the Castle logs so cannot speak to this.

[@dennis3004psp]

have you use a sensor wire?

[@Blueknight1960]

@@dennis3004psp Yes I have and imo, it's great.

[@inhimwelive3951]

Can we please also get a understanding of timing, if you have another video for this ignore this comment cuz I'll be researching now

[@RCJuice]

We do not have a video, but if you are familiar with timing in an internal combustion engine it is essentially the same thing in a motor. The timing is the point in the rotation of the rotor at which the current is sent through the stator windings to create the magnetic force to propel the rotor around. Adding timing will increase power, but the more timing you add the more heat you will build.

[@inhimwelive3951]

@@RCJuice Ya, I do get that but is thr a torque/timing ratio that could optimize the power while still rotating less to help the heat factor? Now that I'm thinking about it I'm seeing it btr in my head. Also, how do electric motors create torque? Is it a turn rate or is it shaft diameter?

[@inhimwelive3951]

@@RCJuice Also thank you!

[@RCJuice]

@@inhimwelive3951 Any time you add timing you add heat, and it is not minor (you can take a motor that runs somewhat cool to severely overheating just by adding a lot of timing). While the physical construction of a motor does have an affect on torque (longer rotors, for instance, will make more torque than a shorter one) the KV rating plays a big part in that. Lower KV's turn less RPM, but make more torque, and higher KV's spin faster and will give you more top speed at the expense of torque and heat.

[@inhimwelive3951]

@@RCJuice The longer motor will create more torque, that I can get. One last question, is shaft diameter a factor at all,say a 7mm shaft for a 3600 kv motor will allow less or more turn rate possibly? Or is the shaft size a nonissue and they come a standard size depending on the motor? If you don't reply it's no problem, thanks for your input.

[@tuberroot1112]

Why bother making video if you don't understand the subject. K is not for "constant" nor "konstant", it means thousands, as in thousands of revolutions (turns) per minute aka RPM. Yes it's not "turns" either, it's a speed so turns per minute. kv represents krpm/volt. Please sort your sound out too. I mean , why bother.

[@SuperPhexx]

yes. this video is just wrong.

[@rogergauthier2769]

It's kilovolt ......anyway I read a physicists comment who was new into rc but said he knew a lot about brushless motors , basically he spewed alot about the physics of it but the jist. Is the higher the kv number like 4000 k. Would have not much torque but a lot of speed and low kv have more torque and less speed . The rpm could be 50,000 for. High kv you will go fast but probably won't crawl or blow sweet donuts easily so something for a sweet slash would probably find something right in the middle remember torque is tug power not speed power, horse power is speed power so say you got a low kv motor , you could probably pull you're dog around in a sled but only do 15 mph .. that's the best I got

[@Positive_Altitude]

Nope, actually you both are wrong. Kv is a "velocity constant" aka "back EMF constant" and it is a term from motor engineering. You can check Wikipedia page "Motor constants" if you don't trust me. Also kinda funny that you say "kv represents krpm/volt" when Kv is measured in RPM/V, not kRPM/V

[@AphexTwinII]

8 minutes to say V x kv=rpm

[@Top-Jimmy]

Not everyone has Einsteins bloodline Mr Experienced.

[@AphexTwinII]

@@Top-Jimmy You completely missed the point

[@Top-Jimmy]

@@AphexTwinII Not all of us especially the older generation 50 - 70yrs did not grasp math to well in school mate. I think he has broken it down perfectly for us older dudes who cannot grasp math too well. That's all bro, I do apologise if I missed the point, But I don't even know what your point is. Seriously bro, I'm not brushed up on quick equations etc and sadly never will be mate. All good, I just hope that you may think a little before posting. I'm guilty of it too don't worry, sometimes I think...Why did I post such a thing. But anyway... Thanks for replying, Take care from an old fart in Australia.

[@simianwarthog]

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