Did I ruin my focboxs

I plugged them both into the battery backwards! spark…and then had to do it again to make sure and a big spark. both of them have just the blue light going and seem ok except when I do foc testing the resistance number and the inductance are fluctuating and not passing the bldc test either. how do you check for faults?

Do they connect to bldc tool?

yes they seem good and normal except those two things

Did you type faults in the terminal tab?

that’s what I need to do. wheres the terminal tab? found it

none. no faults

Right next to the firmware tab if I’m correct.

makes no sense that resistance could double between testing

  1. Connect them to pc.
  2. Check ppm tab for ppm signal input (does it move when you push throttle?)
  3. Do a few bench tests with remote
  4. Check again for faults

everyone was so flabbergasted by this (myself included, i see it now)


didn’t even notice that the polarity was reversed

small chance that the TVS diodes saved you… but they are probably busted

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yup that was it!.

strangely I get different resistance doing the foc test when I hold the rotor fixed or let it move. 3x differences. maybe that’s just how it works and my real problem is the bell is slightly held back from hard epoxy on the rotor and a tiny airgap…or no airgap in place. So I have other things that could be the cause other than the focboxs. they seem fine otherwise.

@Blasto so what you think. even if the diodes are shot am I ok

You should be fine.

maybe not shot… depends how long you held the power in place. but the size of the spark probably scared the shit out you lol (it’s a dead short)

Check battery cells for voltage. You have a very real chance of cells being under 1v.

does the changing resistance while doing the foc set-up make sense? connections are all pretty solid and it will fluctuate all over…but if I hold the rotor still vs let it rotate a bit while doing the resistance test it makes a big difference. I wouldn’t think the rotor would be at all involved in the resistance test

they’re good. 17 v on the realtime data with 4s…actually that’s higher than it really is. hummm

The test should be done with motor spinning freely. As far as resistance goes. I don’t know if it’s good or bad. It makes sense that you get different readings under different load. With load the focbox has to work harder to get the motor spinning.

but resistance being electrical resistance of just two or one phase (I think it does one)…the rotor isn’t important. I’ll test with rotor off.

strange how it shows my battery like a volt and a half high

Hmm… very bad sign it is… doing extensive testing before risking your life on that plank of death you must…

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