V5 motors keep dying

Which would work except that’s not the issue with these motors lol. You’d know if you read what Levi had to say mbruh.


Had one die today. Is there an update to this?

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We killed one more as well since my last post. Opened it and the board says Rev 10. We now open every motor and make sure they are Rev 7. Wonder what happened with Rev 8 and Rev 9, VEX went the Microsoft Windows naming way?


I don’t know if you understand this situation. The motors aren’t being locked up, they are:

Also, just had our first new motor die :confused:

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We had about 5 die on us last season. We opened 3 of them and they all say Rev 7. As far as usage or programming pattern, they just all seemed to be random for us. We have since bought anti-static spray and that has seemed to help (knock on wood).

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This seems like a big issue that could make or break the remainder of the season.

Why don’t you share details of what you know so far with the rest of the community?

There are plenty of experienced electrical engineers among mentors, that would be happy to look into the problem and share some thoughts.

For example, are you collecting student code that was used to run failed motors vs your test code?

If you determine the failures to be associated with the specific usage pattern then, in the ideal case, you may be able to fix it with firmware update.


@levipope 2 of our motors died after we quickly changed the direction of the rotation. (It was a blue cartridge.)

Thanks to the information on this post we have successfully reproduced the issue and know what is causing the failure.

Essentially, if you are running the motors at a high RPM and then change direction quickly (as mentioned by @Vikram_Bansal) the voltage on the power rail will exceed the limit of the diode and cause it to fail. This is easy to replicate using voltage mode to control the motors. However it still may be possible in other modes as well.

We are testing a firmware fix now. But anytime we make a change to these motors we have to do a lot of testing to make sure we did not cause any other issues.

I hope to have more information for you tomorrow.


I can confirm with a fairly high degree of certitude that our Rev 10 motors died when controlled directly with voltage whether attempting our own version of PID or some other motion profiling technique. Also makes sense that our crazy twitchy driver burned many drive motors as we switched the drive code to voltage bypassing the internal velocity PIDs. We suspected it for a while but were never able to reproduce it. We also were baffled by the fact that our flywheel still runs until this day (hope I’m not jinxing it) on 2 Rev 10 motors. It all makes sense now, we never reverse direction there.


We are still testing the motor firmware update that should help with these issues. We hope to at least have a beta available next week for teams to try. Until then, we are recommending that you do not run the rev10 motors above 11 volts when in voltage control mode. What we have found in our testing is that if you keep the voltage below 11v you can change directions quickly without damaging the motor. Granted there may be some edge cases that we have yet to discover. This will be a temporary work around until we can get a firmware update out next week. Thank you for your patience and best of luck to those competing this weekend.


Will the firmware fix force limit to 11 Volts?

Is the motor fw user upgradeable or we need to send motors back to Vex?

Found 2 motors that are Rev 9. Do those have the diode issue as well or it is safe to run them with 12 V?


Interesting to see Vex’s response to this compared to blown ports. While I can understand wanting to get a fix out quickly, which a firmware patch can do, I would also hope that a Rev11 motor would fix the diode problem directly. The fact that there are “Rev X” versions of motors would indicate to me that there could also be “Rev Y” version of Brains, which could add ESD protection to Smart Ports as several folks have suggested.


Just curious, what is the firmware mechanism to fix this? Is it capping the motor voltage to 11v? Or is there a way to apply some kind of slew rate to the voltage control, or is there some other way that this has been done? Trying to understand the potential motor performance ramifications of this update. Do rev10 motors have separate firmware from rev7 motors?


So our goal for the firmware update was to manage the voltage spike from the motor while still maintaining motor performance. After a large amount of testing and multiple different strategies we have not been able to meet both of those goals. So a firmware “fix” is not going to be the solution.

We are currently working on the procedure for returning these motors. Once we have those details we will share them here.

Only Rev 10 motors have this issue.

Slewing the motor power was one of the strategies we tried but in order to dissipate the power build up in the motor the rate had to be extremely slow. Also all of the motors run the same firmware, but the motor firmware does know some information about what version of hardware it is running on.


Firmware fix was never a viable option, imo.

Sure, you could limit motor power to 50%, if that’s all that diode could dissipate without dying.

But then you have to limit the power on all motor revisions, or it would be unfair to people who bought rev10.

Then people will have to redesign their robots and strategy, because 1 motor flywheels no longer work, etc…


Are there any news on this? Teams are hurting here without motors…


@levipope Any updates on the situation?


Do note that VEX Robotics is closed until January 2nd for the holidays. Don’t expect responses from engineering team during this week.

Enjoy the break! and thanks to the moderators who are volunteering their time to keep posts following on the forum during the break.


We will be making an official post with all the details on this topic soon. But I did want to post a quick update to let you know where we are on this.

Here is what we have been working on:

  1. Creating a new RMA process for Rev 10 motors.
  • With the large number of motors that are affected by this issue we needed a more efficient way to process the returns. Our new process will be more efficient for both you and our support team.
  • Our goal is to get these motors replaced and get good motors back in your hands as quickly as possible.
  • As this issue mainly affects competition teams, we are prioritizing teams in this first round of replacements.
  1. We have submitted the fix for this issue to our production team.
  • Our production team is working hard on getting as many of these new motors produced as possible.
  • We will be receiving shipments of good V5 11W motors in the coming weeks.
  1. We have created software to detect Rev 10 motors.
  • We have a V5 application that you can download directly to your V5 from here: https://v5motortest.vex.com (Chrome and Edge browsers only)
  • This application will allow you to connect 11W motors to your V5 brain and detect if they are a rev 10.
  • Of course this process will only work for motors that are still functioning. If the motor is dead you will have to identify it another way. All of this will be explained in our official post.
  • You can go ahead and use this application to start collecting any rev 10 motors and get them ready to return. When the new RMA process is announced, hopefully this will allow you to get these motors replaced quickly. Please do not try to submit your working Rev 10s for return via our normal RMA process.
  • If you don’t have enough non Rev 10 motors to replace all of the motors on your robot, be strategic as to where you use your Rev 10 motors. Any motor control group that is not using voltage commands should still be a safe place to use Rev 10 motors.

Again, there will be more details in a future post. I just wanted to make sure everyone knows that we are actively working this. Please let me know if you have any questions about the Rev 10 motor detection application. I know you will probably have a lot of questions about the return process but until it is finalized I don’t have a lot of answers for you. Once the official post is active we will post a link here.


Here is the official post about how to get rev 10 motors replaced: