300KV Motor, Trying not to fry vesc, help

Hey! I hear if the motor spins too fast, have too high RPM it will fry the VESC, so how can I limit it and prevent it?

This is the motor I have http://alienpowersystem.com/shop/brushless-motors/aps-6374s-sensored-outrunner-brushless-motor-300kv-3200w/

Thank you.

Anything over 7s will be above 60k ERPM which is vesc limit. Most people use lower kV motors so you can run higher voltage less amp draw.

Also you can limit ERPM limits on the vesc to 60k/-60k. Make sure you do not check the box that says limit ERPM with torque. I’ve heard it applies the brakes at full speed.

Well, im using 12S… So thats why I asked, but the torque should be fine because I have a gear ratio of 2.6, which means the motor gotta turn 2 rounds to turn the wheel 1 time?

I only see “Limit ERPM with negative torque”, so I gotta uncheck that one and limit the Max ERPM to 60 000?

Since I have a 300KV motor with a 12S setup, it means it will draw much more amp, and the battery will drain faster?

If I had a 100KV with a 12S setup would that mean it would draw less amps?

Limit ERPM with negative torque is the box you need to uncheck. There is no advantage to using a 300kv motor with the erpm limited to 60k Since the 300kv motor has less torque, you might draw higher amps and you may experience problems with the motor overheating.

You would be better of to see if Alien will let you return that motor for credit on a 170kv motor.

Thanks, but overheating is not a problem. It will be sealed with oil. Hmm, if I had the 170KV motor, it would be around 47kph, on 44.4V, thats why I bought the 300kv, because of much more speed… so I would always be able to limit it to 50kph so I wouldnt feel powerloss when the battery is at 3.3, because it would still be able to drive in 50kph. But if I had the 170KV motor I could change the middle gear to a 30 teeth instead of 25 teeth, and the other to 10 teeth.

Getting to that speed will be a problem with no torque, unless you’re traveling 1 way, downhill :wink:


So you say I should change it to the 170 kv? If I do would i reach 50kph with no problem?

With the right wheel size and gearing at 12S should be very doable You could use a 190kv motor, assuming most are actually lower kv you’ll be at the limit with 12S

@scepterr btw, shouldnt my gear reduction fix this issue with the 300kv motor? My gear ratio is 2.6 “While in many applications gear reduction reduces speed and increases torque” The wheel is 90mm.

I’m doing 50kph on 190kv 10S 15/44T 107mm and I haven’t hit my top speed yet Edit:40 not 44

Cool, but you have the opposite of gear reduction which gives you more speed and less torque, mine gives me less speed and more torque. Well if the torque is that bad, I will return it.

You have a gear ratio of 0.3 I have 2.6.

Sorry it’s actually 40T not 44 and it’s 2.67 ratio… http://calc.esk8.today/config/?type=3.7&scells=10&pcells=3&cc=3.0&da=20&mda=60&kv=190&poles=14&eff=90&wheel=107&mp=15&wp=40&wpm=18

oh, mhmm, well here is mine. http://calc.esk8.today/config/?type=3.7&scells=12&pcells=1&cc=5.2&da=20&mda=60&kv=300&poles=14&eff=97&wheel=90&mp=25&wp=65&wpm=18

So should I just return it? Or just test it out my geared hub motor when it is finished?

I would exchange if possible

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Ok, I have contacted them. But that means I gotta make a 30 teeth gear now for reaching 50kph with ~3.3V. So the gear ratio will be 2.17.

You need the basic 15/36 90mm setup…


Lol, cant do that. I have a geared hub motor. With a planetary gear.

Oh well I dunno then :yum: I was wondering where you were fitting 66teeth…lol

Well, thank you any way :blush: