What is FOCBOX (vescx) ERPM Limit?


What is FOCBOX ERPM Limit? I read vesc 4.12 generally use 60,000~80,000. I know focbox is based on 4.12 but is it still the same ermp? on website it doesn’t state anything tho

I know default is 100,000 and this seems to cause drv fault.

Erpm is 60,000

Ive seen video of the FOC box at 84,000 erpm on an ebike.

exactly, it doesn’t seems to have issue passing 60k it just get inefficient right?

I think the margin of safety past that speed is reduced so chances of failure are higher. Definatley a good idea to keep it @ 60K or below. My 12S 130KV 28 pole hub boards is pushing that limt on a full charge as well.

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I see thanks for advice, I will stick to the 60k

It’s a HW 4.12 at heart, so the limit should be the same.


The ERPM limit was figured by @chaka through a trial and error process. The Infineon hex fets are big and slow compared to directfets.


VS Directfet

Now add some slow fets with bad decoupling, then you have a very noisy circuit with a 60K erpm limit.

I’m sure if @chaka would do his testing with his directfet design his results would be different.


so the old mosfet was main problem. I guess it would be okay to say there is bit more head room. I actually seen a video testing 100k on focbox. didn’t seem to trigers anything. thanks for info it was very helpful

The 60k erpm is mostly determined by the driver and the lack of the third current shunt resistor. I have found some MOSFETs that look better on paper than the direct FETs but there always seems to be a trade off on rise time VS resistance. One thing that can be done with FETs that have a low gate charge and high resistance is run 12 to spread the thermal dissipation?

We really do not need to go above 60k erpm in eskate. @trampa If your machine needs to go that high you have a poorly designed build. From what I have seen in eMTB’s you are actually running much lower than 60k.


Our customers have all sorts of projects on the boil and some need more ERPM. Good to know that 150K is possible now.


Yes of course, but it is better to run at a lower erpm for high current applications. The higher switching speed seems to effect the “on” resistance.

That is up to the developer of the equipment. The higher ERPM gives them a bit more freedom to use different motors. We use quite low KV motors.


that’s true, higher rpm gives more economic efficiency. as of most low kv motors in compact size is not easy to make and expensive.

I get that but this is an eskate forum and it is best to speak in terms of what works best within our constraints. Your information would be better suited on an RC forum, marketing wise I think you will be able to attract users who could utilize smaller high KV motors.

This type of marketing here generally just causes confusion to new builders.



I didn’t start that ERPM topic. I do also recommend low KV setups for ESK8. :wink:


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