To Propulsion Boards Re Duty Cycle Current Limit Start

I bought a @PropulsionBoards Demon 2.0.
For the most part I like it. I think it’s a good choice for a guy like me who just wants to take a board out of the box and go riding and do all their learning later.
(I know it doesn’t get much respect from some of the DIY guys around here) :slight_smile:

I do have a couple issues tho and one of them is the default they use for Duty Cycle Current Limit Start.
I’m gonna send them this email in case they aren’t monitoring this board.
I think it’s pretty important as a safety issue.
Hopefully I’ve summarized the board’s feelings on this issue fairly well.
If anyone has suggestions lemme know - I haven’t sent it yet.

Hi guys,

I have some info about your VESC settings that I wanted to pass on.
I’ve been hanging out at (where you’re a member).
The concensus there is that the setting “Duty Cycle Current Limit Start” must be changed from its default of 100% to 85%.
The reason is that with setting of 100% the motors allowed to go all the way to 100% duty cycle and then power is suddenly cut.
A rider leaning forward against acceleration will likely be thrown over the front by a sudden power cut.
With a setting of 85%, current will ramp down smoothly between 85% and 100% duty cycle.
To the question of “If 85% is safer why is it not the default?” Trampa replied on that VESC is used for many types of vehicles aside from skateboards.
On a self-balancing vehicle it’s important not to “give up” and let the vehicle overbalance and fall at 85% duty cycle. Thus 100% is used as the default.
Skateboards should always change this setting to 85%.
I did have one high-speed wipeout from sudden wobbles and I’m kinda scratched up as a result. Was it a loss of traction because of a sudden power cut at 100% duty-cycle? It’s hard to say - it all happened too fast. I think it’s more likely that I just got the wobbles from going too fast too soon and that I’ve never actually gotten this beast to full speed.
Nonetheless I do worry that that was the reason.
I think you should make this change on all the boards you sell from now on.
There’s a small top-speed penalty for this change but the safety increase is worth it and I think this board has plenty of top speed to spare.


p.s. – It’s important not to confuse Duty Cycle Current Limit Start with the similarly named Maximum Duty Cycle which must stay at 95%


Nice summary. Good on you for not being a fucking jerk about it :+1:


Well said. For me, it felt like my motors were oscillating/wobbling back and forth at high duty cycle. It felt like the motors were stuttering a bit or like traction control was out of sync and they were both trying to sync up again with the other motor.

Did it 3-4 times before I decided it was too scary to keep testing at near full speed.

Hope you’re all recovered man.

My one edit would be matching the title to the vesc tool.

“Duty Cycle Current Limit Start”


Excellent point I’ve edited the OP and added a P.S. since it so easy to confuse with the other similar setting.


Propulsion noticed this post and emailed me before I sent the email.
They said they are going to talk to their esc supplier about it - so they are taking it seriously which is good.


Yes so we now do limit it to 85%. Seems to have helped with preventing any cut outs thus far!


How the hell have you guys been shipping out boards with the duty cycle limit start at 100%, that makes me wonder that if in all the riding you did in your videos, you didn’t once go full throttle or near your top speed?
How could you ship boards out to customers with an inflated price, but not once go full throttle or near the top speed with your boards? I’ve rode my esk8 with the duty cycle at 100%, and going full throttle nearing 25mph+ it will violently jerk you back. Here’s a video of full throttle w/ 100% duty cycle:

You’d think to read up on VESC settings before selling people esk8s with vescs right?


That’s a screenshot from a website right?
I don’t know if it’s entirely fair to say they should have read some particular web page.
The setup wizard should help you get this right if it’s so important that this page put it in red capital letters. I mean what is a setup wizard even for if it doesn’t help you get correctly set up?
I would put the blame if there was any to be laid on whoever insists making this change to vesc tool is not important and is not making it a priority.


Yup, it’s from the VESC website. I agree that it should be emphasized in the setup, or automatically enlisted, but nonetheless, it’s no excuse to ship customers boards like this. These are boards you’re selling for an inflated price, and they should come properly configured.
As you can see in my video I was nearly thrown from my board because it was at 100%, but that is likely an extreme example, considering I run BLDC sensorless.
No hate towards @PropulsionBoards though, you live and you learn, it’s just infuriating thinking customers boards could hurt them due to improper settings.
EDIT: One more thing, @PropulsionBoards, you should send emails out to your customers with instructions on downloading VESC tool and configuring the Duty Cycle Current Limit Start to 85%.

Totally understandable we should have known about that before sending out boards. We had a couple other customers reach out to us with that problem and we made a video on youtube on how to reprogram it. We also sent out an email to everyone that bought one telling them about it and giving them a link to the video.

Also not to throw MBoards under the bus and no hate towards them but we watched his programming video and saw the same mistake and reached out to him to let him know.


Props for taking responsibility y’all!
Best of luck to you guys.