Why Did I Stop Accelerating / Help Me Troubleshoot (SERIOUS)

I’ve been thinking about this post for over a week and then today I saw a Facebook thread about a fall from a “remote cutout” and that pushed me to get this done.

Quick Background:
I just completed my first build (build thread coming). Specs - Torqueboards DD, Unity from bio-boards (they modified it to an XT90 and 5.5 mm bullets), 12s5p 21700b battery pack (my first ever build) bypass / charge only BMS, Hoyt St. puck. The Unity settings - 60 amp battery max, -60 amp brake max and 60 amp motor max.

I’ve got about 20 miles on the board due to quarantine issues. It seems to run really well except for the issue below…

The Issue:
In two of my test rides I’ve experienced a sudden loss of power / acceleration. I didn’t fall as a result of either, but I’d like to get to the bottom of the issue to increase my confidence in the build.

Here’s what it looks like on video (about the 10 second mark) - https://youtu.be/WzAGoRQaOjA

What I Know:

  • In both cases the issue occurred while riding up hill under heavy throttle.
  • In both cases I had plenty of charge left.
  • In both cases the remote worked as expected immediately after the incident. I did not have to power off the remote or reconnect after the issue.
  • I did not check the Unity for faults after either issue. I didn’t know that was a thing until today, so * I’ll be sure to do that if this happens again. Any info on how to do that would be greatly appreciated.
  • Both times this happened it was cool and the ESC temps were low.
  • Same with motor temps, I grabbed and could hold the motor cans after each time.
  • Both rides were in the middle of nowhere, so it’s unlikely that radio / electrical interference was the issue.

What other data would be helpful?
What other questions should I be asking?
Someone please help me try to sort this out so I can be confident in my board!

Thanks!

1 Like

Does your battery run through a discharge BMS?

1 Like

No, charge only.

Latest firmware on the unity?
Do you have motor thermal throttling on?
PWM is calibrated? No ERPM limits?

23.46 I think, I’m trying to connect now.
If motor thermal throttling on is default then yes. If not no. That said, the cans were only warm to the touch.
PWM was calibrated.
Checking the ERPM now.

Turn off thermal, sometimes the temp sensor can be off etc.

1 Like

Ok, will do.

Confirmed I’m on 23.46.
Traction control is off.
Not sure where to find eRPM. I see 3000 eRPM under the traction control option, but it looks like that’s disabled.

Just curious, would thermal throttling produce such a sudden and strong response?

Weird. If you didn’t go through the focbox tool then there should be no erpm limit set. Thermal throttle starts turning power down, it’s not full power cut but it does feel somewhat sudden. I would keep it off tbh. Nothing in your setup looks like it should be cutting power. The only thing I can think of is depending on where you have battery cutoffs set, you might be hitting the cutoff under load even when the battery is not dead. You’d have to see what voltage the ESC is getting. Where is your cutoffs set btw? And any constraints in the wiring possibly?

Battery cutoffs are the default - start at 40.8 and end at 37.2.

I don’t think there would be wiring constraints, but I’m not totally confident in saying that.

I also don’t understand how a wiring constraint would behave like this. If I was hitting a wiring constraint I would expect it to be reproducible - same hill, same battery charge level, same throttle -> same issue, but that’s not the case.

Thank you for this back and forth, I really appreciate it!

Hmmm. So it’s not consistent… That is very puzzling. Everything on your settings look right and the hoyt is not really known for disconnects… Unless someone else has an idea I’m not entirely sure. It does sound like a load issue if it only happens on uphill, but other than motor thermal error I can’t imagine what it would be. Unless someone else has an idea.

I suggest reflashing the firmware, just have it upload again, then do motor detection and setup one more time, and disable motor thermals. If it happens again, don’t let it power off until you connect to the tool and run for faults.

3 Likes

I was experiencing something similar the other day; I was getting a cutout due to the motor temperature exceeding the max value, which was due to a bug of FW 4.02 not filtering the data correctly. You’re using a Unity however, so I don’t think you’d have the same bug, but maybe a faulty temperature sensor in the DD could be doing the same thing.

f you have the protective gear for it, you could try using vesc FW5 which has Unity support, and then if you manage to reproduce the cutout, type “faults” in the terminal tab of vesc tool to see what caused it.

Edit: bad idea; you can list faults with the firmware you already have.

4 Likes

I wouldn’t suggest FW5 it’s still quite experimental atm. 23.46 is proven to be stable for most atm. I agree though, turn off motor thermals. Other than that, possible drv fault but seems strange.

1 Like

First off, nice recovery. Is there any chance your phase wire bullets can be coming into contact with each other?

1 Like

I get something like this on one of my boards, and have yet to figure it out.

1 Like

I just don’t know if there’s a way to check for faults otherwise; + it has the most bugs fixed out of all the firmwares :stuck_out_tongue_winking_eye:

1 Like

I’m not sure the ESC can recover from a phase short and act normal after… Also doesn’t make sense it only happens uphill…

5 Likes

@BillGordon Thanks! I don’t think that’s it, I added heat shrink around the bullets to would prevent that. When I pull the enclosure I’ll check again, but it seems unlikely.

1 Like

You can connect 23.46 to focbox tool and run faults just like on the vesc tool…

Also the only 2 times I’ve ever had unity cut on me on 23.46 was when a flipsky motor (yup) was giving bad temp readings. Turned that off. Another was traction control caused 1 motor to overheat and desync due to a kV differential. Now with both off, never had a cut other than low battery.

3 Likes

Proven stable is a pretty big thing for me. I’m too old and have too many other important things going on in my life to be an ESC tester. As much as I’d like to use the new Lacroix app, I’ll stick with what’s known to work.

3 Likes