What does KV Rating Mean on a Brushless Motor?

[@RCKnockout]

I did make a mistake in the video that has been pointed out to me in the comments….I was multiplying the voltage values listed on the batteries which would be considered at storage charge…a fully charged Lipo battery holds up to 4.2 volts per cell so I should have multiplied 12.6v and 16.8v for a 3s and 4s by 2100kv and 3500kv to get the maximum RPM with a fully charged pack…so keep that in mind when watching the video, thanks guys

[@cds1223]

That’s exactly what i was looking for. And the weight/size of that motor spinning at that kv makes the torque. Si?

[@RCKnockout]

@@cds1223 glad you found it helpful! Well torque and rpm are different….the initial torque is typically gonna be higher with a lower kv motor compared with a higher kv motor

[@aaronschmitt2120]

Good explanation, can't tell you how many times I've had to explain this to people. Only thing you missed, lipo batterys at full charge are 4.2v per cell. So a 3 cell full charge is actually 12.6v. so the 3500kv motor is spinning 44100 rpm on a fully charged 3 cell lipo. Also as a general guideline, you don't want to go past 50,000 rpm on a motor. Also more rpm= more heat, and heat is what kills motors. Otherwise we all would be running 5000kv motors on 8s lol

[@robaki-dev]

Most of the motor's heat comes from I^2R losses in the copper windings, which increase with the current draw depending on the motor's load. Theoretically, a motor could run at max RPM without overheating if there's no external load on the shaft, due to no current flow. And you could fry the motor in second with stall current at 0 RPM.😃 In reality there's internal friction and minimal current flow. Overgearing to make up for a lower KV motor increases the load on the motor under any driving condition at a given speed, compared to a higher KV system with a smaller pinion gear. I suspect such a setup is less efficient.

[@RCKnockout]

Yeah I totally wasn’t thinking when I explained it about the voltage on the batteries being at storage charged not fully charged…same math though…just times the kv by 12.6 for a 3s and 16.8 for a 4s to get Max RPM Heat definitely is the fastest way to fry a motor though lol

[@Rc-Krazy]

So higher kv more torque and more heat. The lower the kv the more top speed you can produce with gearing. Thanks for the explanation. Sub earned

[@RCKnockout]

Higher KV is more RPM but more heat….Lower KV is more Torque and less Heat but Less RPM but it can be made up with higher gearing ….I appreciate the Sub!

[@JavierFlores-hs2fc]

Thx for posting this

[@RCKnockout]

You’re welcome 😉

[@SHADoW.ST0RM524]

very helpful i have a ftx carnage and didn't know what motor to get and esc {: thanks sub like and bell earned

[@RCKnockout]

Appreciate it! Glad you found it helpful!

[@slashraptor9317]

Great video but I do need to say you’re doing the math with the voltage around storage charge try it with the full voltage for the 3500kv I did 12.6x3500=44,100 just a little reminder

[@RCKnockout]

That’s true…it’s definitely easier to explain to someone using the voltage printed on the battery…but I did totally forget to factor in all the cells charged to 4.2v….thanks for pointing that out….I’m sure you won’t be the only one lol

[@yorkrojas1452]

This is exactly what i want to do, not more speed, its fast enough to be fun, i just want to run longer before overheating and want to run it on grass too.

[@yorkrojas1452]

Wow!! Thanks!!!

[@RCKnockout]

You’re welcome!

[@RaiderDave42069]

if I were building a monster truck for max pulling power, would lower KV be better?

[@RCKnockout]

Yeah a lower kv would definitely be better for pulling…it’ll stay cooler and it will have more torque

[@Name-nq4oz]

can you run a 2 pole motor on a 4 pole esc

[@RCKnockout]

Honestly I’m not sure…you might want to contact the manufacturer to see or check the ratings of the esc

[@ronnyweinreich9425]

If you gear both motor to the same RPM at full speed, is there torque at the end the same?

[@RCKnockout]

No it wouldn’t be the same for both motors if they are both geared the same…the higher kv motor would have significantly more wheel speed

[@ronnyweinreich9425]

@@RCKnockout I've meant it the ther way, so that both motors geared to the same wheel speed. For example. 2000 KV × 11.1 V / 2.22 Gear-Reduction = 10000 RPM 3000 KV × 11.1 V / 3.33 Gear-Reduction = 10000 RPM If both produce the same wheel speed, which ohne has benefits over the other?

[@RCKnockout]

@@ronnyweinreich9425 no if the final drive is the same…then there theoretically wouldn’t be a benefit of either….granted the lower kv motor would probably be more robust and therefore more likely to last longer overall

[@ronnyweinreich9425]

@@RCKnockout thanks for the answer. 👍

[@RCKnockout]

@@ronnyweinreich9425 you’re welcome!

[@connorfast8494]

Can you gift me a slash setup, my slash 2wd is still stock

[@RCKnockout]

The 3500kv in the video is cooked…was only showing it for illustrative purposes