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VESC FAQ | Limit output voltage according to motor maximum specs

Hi,

I’m new in VESC utilisation. I was wondering if it’s possible to limit the VESC output voltage according to the max motor voltage.

Why ?
Simply because my actual motor is 10S max (Aerodrive SK3 215kv), with a 6S max HobbyKing ESC. I’ll upgrade to VESC, with 2x 6S attery and I 'would not change my motor …

Is it possible with this device ?
I already found there is an option for rpm limitation, but i’m not sure it will be enought to avoid firing my motor …

YES, you can do it.

In BLDC tool / Motor Configuration / Motor

This is recommended for anyone with 12S Battery & Motor over 200KV

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@onloop could you elaborate as you why? I was planning on using 2 6s in series to make a 8000 mAh 12s to run 2 VESCs and a dual drive carvON. I don’t want to damage the VESC, but by my math, a 12s can max out at 50.4 volts (4.2 per cell X 12 cells), which is well under the 60 volt max limit for the VESC.

The enertion shop page says up to 60 volts or 12s, but 60 volts would be a 14s, so can the VESC run on a 14s battery?

this reason…

I get that but what’s the science behind it?

Voltage rating of the components in the VESC.

Is that true ?
I thought that VESC was not recommended when used with 12S voltage and motors over 200KV.

Sorry, I misinterpreted the question.
Some interesting reading material that might shef light on the subject.

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@onloop @trbt555 Could either of you elaborate on how to properly set the voltage and current limits on VESC? What you base the values on? The motor’s limit, or the battery’s potential output, or some combination of those? I’ve not found a place where anyone describes how to derive the right values. @trbt555 I know you’ve written at least once about exceed VESC’s threshold and have your power cut off. How do you avoid that now?

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@treenutter I’m by no means experienced after only 4 rides but I’ll share nonetheless, for what It’s worth.
I posted about voltage cutoff in my build thread. If you look at my discharge curves (or any lipo curves on the net for that matter) you’ll see the voltage drop steeply past 3.6V per cell.
So on my last ride I had the voltage cutoff set to 3.6V x 12 and I quit riding as soon as I felt the power drop. Worked pefectly, my charger told me all cells were perfectly at 3.6V and the 5000mAh Zippy’s soaked up about 5200mAh on my charger to get back to 4.2V.

Unfortunately discharge curves don’t tell you how much the cell voltage sags under heavy load. Because I had my cutoff set too high initially, I was hitting it even with charged Lipo’s just by accelerating fast, just because my lipo’s couldn’t keep up. I think.

There are settings for both motor and battery current limits. As I’m using the R-SPEC’s I left the default motor settings alone, and set the battery current limit to match what people were telling me my lipo’s would be capable of and just above the max current my wattmeter was reading.

Hope this helps.

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Just to give you some indications, you should adjust it to your experiences:

“min. Input Voltage” = you can leave that at 8V “max. Input Voltage” = you can leave that at 50V, except for 12s = 57V “Battery cut-off start” = number of cells x 3,5V “Battery cutoff end” = number of cells x 3,3V

Table:

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so would your VESC cut out at 3.5v, or 3.3v with these settings?

It would start slowing down at 3.5 and cut out at 3,3 (or 3,2 which is also ok). Advantage: the VESC will not just shut down at one point but indicate that you’re reaching the end of capacity so that there’s time to get acquainted to the fact that you have to stop skating. :grin:

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awesome, that’s exactly what I was looking for.

Thanks!

And what about these parameters ?

Does the VESC will limit output voltage according to the “max. Input Voltage” value ?
For exemple, if I ride with a 12s battery (=57v), but this parameter is set to 50 (= 10s), does the output will be limited/regulated to 50v ?

I ask this because my motor is limited to 10s, but I plan to ride in futur with two 6s battery, so I’m looking in a way to limit the max motor voltage.

It would limit the input voltage to 50V, yes. But my experience of limiting the Voltage that way wasn’t very exciting, the motors behaved strange (stuttering when going fast). You could give it a try though.

I don’t want to fire my motor !
Do you know a better way to limit the motor violtage ?

(but I will did a try when I’ll receive my VESC, with a 6s battery associate to a “software limitation” of 3s …)

12S = 57V ?
Please elaborate.

It was suggested by Benjamin, but I don’t know the reason behind it except maybe to stay within the 60V limit.

Sorry I did a mistake :
10S = 42v
12S = 50v

Shame on me…