Question about duty cycle current limit start?

Esk8 Electronics
1

What is duty cycle current limit start(VESC)? The reason why I ask this…I was losing brake power for 3 sec. Like no power. The original setting was 100%.

When I updated my VESC software. I noticed I see e skate on the motor tab settings. The duty cycle is 85%. The problem was gone. What is this because I almost busted my ass.

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2

There are two different settings here.

1 - duty cycle = 95%

2 - duty cycle current limit start = 85%

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Can you example what they do? Ever since I updated my VESC software. The new E skate tab show up on my motor settings. It fixed my issue. Before… I used generic tab with 100% for duty cycle current limit start. That failed alot when I was riding. No brake and cutout on full throttle.

4

Are you using a puck? Make sure to calibrate ppm on remote mode 3. Otherwise cutouts.

Also set your duty cycle settings to what other Evan said above. 100% is unsafe.

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5

No Puck. I’m using 2.4Ghz Remote VX1. The problem was gone when I selected e skate tab for my motor settings. I wont use the generic tab anymore.

6

The duty cycle current limit start behaves differently depending on the firmware version.

Firmware pre 5.0 can be left at 100%
Firmware from 5.0 to 5.2 need to be manually turned down to 85%
Firmware from 5.3 onwards has it already set at 85%

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7

(if only u choose electric skateboard during wizard setup, all other selection still put it back at the default value)

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Max duty cycle – determines after which RPM VESC won’t drive the motor faster anymore. If you exceed this value you can still brake, however. (But if you brake at more than 100% duty cycle you might kill your ESC) (Use this value instead of Max ERPM to set a speed limit on your board.)

Max duty cycle current limit start – determines the max duty cycle mulitplier (as of FW 5.3. On earlier firmwares this was an absolute value for the duty cycle) at which the ESC will decrease current from as you reach max duty cycle.

For example, with the default values of 95% duty cycle and 85% duty cycle current limit start, and full throttle on the remote:

  • From 0% to 81% duty cycle (0.95 x 0.85) the ESC will drive your motors with the max current it can (based off of motor current and battery current, depending on the duty cycle).
  • From 81% to 95% duty cycle, the ESC will gradually decrease the motor current you try to drive your motors with. At 95% it will limit you to 0A, and at 81% you still have full power. Whether this limiting is done as a cap to absolute motor current (I hope not lol), or a multiplier of whatever you’re inputting from the throttle, I do not know.

Obviously at 0A your board is going to decelerate, so your board will naturally even out somewhere between 81% and 95% duty cycle. If you want to squeeze out every bit of top speed out of your board, you might want to decrease this gap or eliminate it entirely, just be careful of the sudden power loss as you approach max duty cycle. This is why I personally overgear my boards so that my theoretical max speed is higher than what I actually want to ride at.

(And yes, since from 5.3 onwards duty cycle current limit start is a multiplier, you can set it to whatever you want. I recommend 90% or lower, but feel free to set it to 100% to disable this safety feature completely. I personally set it to 80% on torquey setups to make sure I don’t kill myself from the otherwise sudden power loss as I hit top speed :sweat_smile: )

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I was on version 5.0. After i updated my firmware. I thought generic motor tab was the right way of doing it. What a big mistake . Now i know after the crash.lol

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Thank you for explaining it. Now i will tell people about this for their safety.

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