Choosing the right motor kv for the VESC

If you have done your research you have probably found a lot of conflicting information about what KV is “best”. Often times this information is given without regard to system voltage or electrical rpm limits. The VESC has an ERPM limit of 100,000 but I have found that limit to be closer to 60,000 ERPM. Vedder has stated that running higher than this is inefficient but I have also found that it causes VESC failures.

My findings are purely anecdotal and I am not completely sure but a pattern has developed where systems designed with the 60,000 ERPM limit in mind run trouble free.

What does this mean and how do you calculate an ideal motor kv for your particular system voltage? It is relatively simple, virtually all the motors used in eboarding have 7 pole pairs, divide 60,000 ERPM by 7 PP and we get roughly 8570 rpm. Divide 8570 rpm by your system voltage and you will have your ideal motor kv. I like to make my voltage calculation based on a fully charged voltage so 12s would be roughly 50v.

8570 RPM/50v = 170kv - 12s
---------------/42v = 200kv - 10s
---------------/33v = 260kv - 8s
---------------/25v = 340kv - 6s

These numbers are a rough guide, you can go a little higher but use caution. If you a want a smooth running reliable system this is a good first step to help achieve that.

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This is seriously more conservative than Ben’s recommendations.
He was saying that 240KV should be OK with 10S.
I think it is because he s using 86000 instead of your 60000.

I hope it is cause that’s what I am planning …

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Oh wow, first bit of information I’ve come across about this. Thanks! So this is again an argument for choosing a lower kV motor (if u use 12s and such) if I’m not mistaken

Vedder actually made his calculation based on 3.8v cell voltage resulting in 225 kv at 10s. You have some wiggle room.

Also an argument for a dual motor 6s with high kv. I often wonder how well a quad drive 3s with 680 kv motors would perform.

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AH …
Thanks for this information about the battery voltage.
I did not remember that part of the calculation.

Thank you for the info
When u say motors typically have 7 pole pairs what do u mean?

What if you plan on running Dual motors?

I mean they usually have 7 pairs of poles or 14 poles total.

Then you can drop your voltage and go with a higher kv due to the shared loading and lower amp use per motor but it changes nothing in these calculations.

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Wouldn’t it be 6 since there are 12 teeth?

@Hummie here we go down the rabbit hole again? What do you mean by teeth?

I don’t know what u mean by poles. There’s 12 stator teeth and 14 magnets typically. How does that relate ?

My vesc is coming from chaka. i will use enertion 6372 190kv motor and 12s3p battery pack from dexter. This configuration should be ok on vesc?

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im 70 percent sure i saw someone post something about 190kv and 12s on the vesc as a sweet spot

Good to know. The plan was 10s3p pack but i get a really good deal on 12s3p here in canada. Was second hand but still good deal

Correct, it works but it is not ideal. You will lose the top end performance an never reach anywhere near the theoretical top speed.

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So 10s would be the sweet spot?
Edit: in regards to lifepo4 with a 245kv motor what would be ideal for the longevity of the vesc

8570rpm/245kv = 35v

35v/3.6v per cell = 9.7 cells

So you should be able to use a 10s lifpo4 pack with a 245kv motor.

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Ok poles being magnets