Blown Focbox .. ( was Help diagnose cutouts. Dual focbox | can bus | 6384 maytech/lacroix motors | flipshit vx1 | metr logs )

Thanks I will definitely check this.

had two other problems on two other boards today. … so haven’t gotten far on this one yet. and now the work week commeth. . [ watch I’ll probably work on it on my lunch break… ]

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That bug applies to all vescs it seems :disappointed:

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By looking at your log I think you had a watch dog reset.
At least your NRFmodule failed to get data points just when you had the fault (between blue lines). Data looks frozen.

Look at the speed, it has not been updated. Sigificant drop when the next valid data was received.

You could trigger a watchdog fault code using vesctool and click reboot. Then check if this code can pop up in your log.

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as a testing mechanism to see if metr can catch the faults? interesting.

I didn’t know about triggering a watchdog fault I’ll have to look into what that is about. it sounds like you’re saying I may have triggered one as part of the event but also i can use it as a tool to test?

good observation on the speed. it suggests my vesc was could have been frozen or rebooting. or that BLE module disconnected for that moment. thanks.

Yes exactly. It doesnt say why there could have been a reset… only to see if the fault code is visible in the app. I don’t use
metr so I dont know what it shows regarding faults. The code will be set in vesctool if you read fauls there.

I had watchdog resets (short cutouts) frequently some time ago after having installed a NRFmodule to that esc.

To pin point the problem I swapped the escs to see if the issue followed the esc with the fault code. But since then I have not had any problems. I did position then nrfmodule wires a bit differently so it is possible that it was the module that picked up interference earlier and disturbed the esc in some way.

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So i decided to blame the flipshit VX1. because on inspection it’s wires seemed sketchy despite my previous inspection and hotglue. one wire at the pot was pretty weak and broke off looking at it. :confused:

I redid the wiring. took it out for a test run… and…

the whole thing locked up a wheel. metr and remote disconnected. it’s dead. the one wheel drags the way it feels when you connect to phase wires on an unhooked up motor. I’m guessing I actually do have a phase short or something and i probably just fried my vesc.

I should have opened it up and inspected it depsite suspecting the flipshit.

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This is highly unfortunate, I’m assuming all of your phase wire connections were insulated?

sidenote - moving to mr60 on my newest build is a good move bc you can’t mess up wire order or have phase short

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they are bullet connected with heatshrink over the bullets.

really want to ditch work and open it up and inspect. WFH is a lot harder in these circumstances.

Bro I know, that’s why I’m in office (we had the option to wfh or be in office), so I can’t just go work on my board and have less distractions… oh wait

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I see no signs of phase wire issues at the connections and no signs of anything else blown except! …

it did blow a fuse. [ see them in the center on the board with the antispark.

one fuse goes to each vesc. naively swapping the bad fuse with the good fuse… poor detective work. it insta popped the good fuse on power on. so something is shorted somewhere. need to think about how to proceed here.

I will probably disconnect the motor now and do the checks to see if it still works.

Then maybe I extract the vesc open it up an inspect it’s insides?

photo, board is stock lacroix prototipo DSS50

vesc towards top of photo is what blue the fuse. which is middle top side of pic.

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I went riding tonight ok. I didn’t fix this thing. I hope this doesn’t make skatan mad.

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so the focbox is foc’d.

question is what caused it? what to do next so I don’t blow another one in it’s place?


  1. With the motor disconnected it spins smoothly. doing the hand tests of shorting phases together it seems to behave as expected.

  2. Plugging any two phase leads from the motor into any phase connectors on the focbox and they drag as if shorted.

  3. testing continuity on the phase connectors on the focbox shows two wires full continuity. between either of the first two and the third wire the other two seem to be charging a capacitor. current flows for a moment. then if i reverse the probes it flows again. on a spare focbox there’s none of this.

  4. The power leads to the focbox also are shorted / have continuity continuously. by contrast on a spare focbox. you get the filling a capacitor effect.

This suggests to me the focbox is foc’d

I think the hand tests of the motor suggest it wasn’t the issue. but how can I be sure? Next I will extract the focbox and open it up see what I can see… what should I see? how can I get to root cause so I don’t blow another one?

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What makes this happen? how do I not do it again? :frowning:

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Do those burn marks go all the way to the brass insert? Do they go even farther? It’s hard to tell. Is the mosfet split in half?

Definitely split in half. Blown wide open.

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Damn. Is there burn marks on the brass insert?

Brass insert?

The brass circle on the top.

That looks like black goo. Can’t quite tell if that’s burn. I think it’s not.

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I’m supposed to be asleep. More later. :). Thx for looking / helping

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