V5 motors keep dying

For those of us at home, how do we identify the Rev 10 motors without opening them up? I’d rather not install them on robots if I can manage it. Thanks!


I would say that any motor with a date code that starts with a 22 is suspect. But that is not 100%. We are working on a way to detect this with software and we will release that when we can.


Sorry for being off topic here but when I saw your pfp at first my heart had skipped a beat. I though that the VEX account had come back again.

(Which hopefully it will never rise from its grave again)


We just had 2 more die the other day.

This one is the motor that spins the intake and the roller mech. Team is attempting to build a sensored roller mechanism with an optical sensor.

They encountered this nasty lag/delay between the time the sensor reads a change in color and the time the motor stops (HOLD). Not sure if electronic, program related or mechanical inertia but this results in the roller being spun way past the intended mark.

The programmer decides to “fix” that temporarily by adding a slight delay and reversing the motor to spin the roller back to the desired position. We warn him not to do that as reversing the motor like that can put a lot of stress and burn stuff. Programmer rebuts with “but our driver has buttons for forward and reverse and HOLD in between and mashes those buttons like a madman and motor is fine”. Fair.

So we try the code and motor does not even attempt to spin but goes dead instantly. We abandon the reverse code and just reduce velocity to the dismay of the team. After a few batteries and attempts at figuring things out the second motor dies the same way.

We opened them and they were both Rev 10 with a “22” date. The only thing I can think of is the fact that we are pushing these motors hard with “spin with voltage” commands in the max 12V zone. But after they die we always revert to “spin with percentage” at 80% or even more conservative. They still die. Did not find a pattern yet. Now we are afraid to test anything as there are no more motors.

Unfortunately we never connected the dots at the beginning of this saga and motors are not labeled and are mixed up in a box so no way of telling what rev is what without opening. I’m tempted to believe that spinning the motor with voltage at 12V has something to do with it but it could be paranoia/coincidence. But every dead motor this entire season was 100% a Rev 10 with 22, that is absolutely certain.


Thank you @district9 for the detailed explanation. I will add steps to our current tests to see if we can replicate in this way.


There are some small screws on the motor that hold the cartridge in, if you take these off, it will decrease the friction and give you a better test of the motors. If they still don’t spin, you can always take apart the motor and clean the internals. It is a little tricky, but you should be able to get it done with some elbow grease and dawn dish soap

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.