Think I just killed my Focbox 1.6 in less than 24 hours of owning it lol

TL;DR: Read from "The acutal issue"

Hey everyone!

So yesterday I got a package. It was my brand new (used before, but brand new for me) FocBox 1.6.

I soldered new wires, bullet connectors and XT-90 and everything was working like it should. I did the setup with the following settings:

  • Motor max: 70A
  • Motor min: -60A
  • Battery max: 45A
  • Battery min: -15A

Today I went on the first test ride. Pumped up and ready to shred. Everything went fine the first kilometers. Temperature was maybe a bit high (60C at max). Then I came to this long long long road where I went nuts. Full throttle most of the time, 45 km/h most of the time and temperature eventually got higher. Temperature reached 70C (probably 80C but I had put my phone down in my pocket so I wouldn’t crash doing 45 km/h.)

So I eventually reached a light signal and had to brake. I braked pretty hard and at some point I noticed I had lost my brakes completely (unfortunately at low speed…). I went on to the side walk to test my accelerator and nothing happend…

I had no choice. The time was now. I was the chosen one. It was time for


I eventually made it home after 5 km of hard pushing without dying or killing my board even more (accidentally pushed my board out in the middle of the road (no cars, unfortunately)).

Time had come, now I had to open my enclosure and focbox. This video speaks for it self…

As the video showed, no damage on the pcb.

image image

Now to the actual issue:

  • My FocBox doesn’t turn on (No lights or anything)
  • My PC doesn’t recognize my FocBox when I plug it with USB in and give it power.
  • I can read 39V power when measuring Focbox negative on PCB and battery positive.
  • I can read 5V from the UART port when the focbox is getting power.
  • Since I can’t turn on my FocBox, I can’t check the terminal for any error codes…


  • Single motor
  • No can-bus used.

I would appreciate if someone had any suggestions on what happend. Like usual, any input is appreciated. Also the bad ones :kissing_heart:

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Really strange. Have you tried charging your battery up? Hopefully the VESC is just set to turn off under a specific voltage, and you just ran your battery dry.


pretty sure he reconfigured it…

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sound like the 3,3V is dead… did you plug it can bus ? Or else it is probably a blown mcu.


@anon64938381 guess what :rofl:

Another one bites the dust :thinking: good job on pushing 5km tho I feel ya xD

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Often you dont see a damage when its under or inside some of the chips. The gate resistor looks burned a bit but maybe its just the picture, I think your focbox was running at the limits and maybe sth wasnt configured right. With the hard brake it was just to much for some components, I would assume.

With my stuff, I always leave a certain buffer for safety. So I know even if something goes wrong, the components still have little room.

Was this in a single or dual config? Does it still turn on?

EDIT: didnt see the text with the acutal issues under the pictures sorry


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@rusins I configured the Focbox voltage cut-off start to 34.5V and end to 33.5V. Battery is at 38.xV

@JohnnyMeduse Can-bus was not connected. Only had UART + sensor + receiver connected. Could be the MCU.@AlanZhou also mentioned that. Would you be able to point out where the MCU is located? Also where is 3,3V?

@seaborder Think I pushed it to the limit :stuck_out_tongue: Could you please point out the gate resistor? It was in a single setup. It doesn’t turn on. No lights or sounds or anything. And power goes through my anti-spark so not because of that.

Thanks a lot for all of the inputs, guys! Really appreciate it!

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Check if C25 is shorted. The Mcu is the big square chip on the same side as the DRV


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This is the one. But Iam learning all that right now so not 100% sure.

Can you maybe make a closer picture of the part I marked?:slight_smile:

Okay Johnny knows much more about that, I think he can help you out more :slight_smile:

3,3V. Measure it! :slight_smile: bild

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Don’t do like me guys. Just made my focbox get a little bit hot and think a saw very little smoke. All good (from my noob perspective)

Anyway. Got it measured. Don’t measure the actual pins like an idiot (me) but connect a jst connector with some wires.


@Fatglottis The voltage for 3,3V is 150 mV. That’s not normal, right?

@seaborder Here is the picture anyway. image image

@JohnnyMeduse Doesn’t look like it’s shorted. Answer above is probably more helpful. image image

You should have 3,3V, not 150mV. Could be this regulator… Or the MCU is blown and it is now shorting the 3,3v rail somehow.

Is the MCU getting hot?

Btw this is a trick if you want to measure tiny stuff. Of course it’s safer the way you did it with wires :ok_hand:t2: image


Just shocked myself lol. stupid.

The orange circled one is not getting hot.

The red circled one is a bit hotter than all the other parts. Not like untouchable but just noticeable.


If you don’t have 3.3V on the 3.3V that not good.

Using diode check on your multimeter check if the 3.3v is shorted to the gnd. If so it is most likely internal damage from the MCU


wait what?


Im sorry, but this is not my special. Can you please elaborate?

That a similar procedure to check the 3.3V, but since you didn’t use Can, the can chip is probably not defective


Do as @JohnnyMeduse has explained above but on these pins. (FOCbox Powered off) bild

Regarding if the MCU (STM32) got hot or not… Its the big chip to the right.

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