FATboy anti-spark switch

Hi guys, today I was working on the anti-spark switch to use together with momentary push button with push to hold to turn on/off features and in the end created bit overpowered really small anti-spark switch.

Main Electrical Features:

  • Controller by MCU
  • High Side switch
  • FDBL86361_F085 Mosfets (300A 80V)
  • 10-70V operating voltage (up to 16s)
  • Theoretically it should withstand 100A constant current but have to test it out before I can give my word on this
  • Any push button
  • 5V led output
  • Really small module (18mm x 50mm)

Possible Software Features:

  • Push and hold for e.g. 5s to turn on/off (prevents accidental turns off/on)
  • Programmable push hold button time
  • Programmable low voltage shut down (somehow programmable with same push button)
  • Battery level by dynamic led blinking times?
  • Ability to disable current intake into the battery

Now have to cram all those software features into small memory footprint.

If anyone has any more suggestion, please comment :stuck_out_tongue_winking_eye:


Sounds good to me… We need more solutions. Just had a high speed spill today thanks to a failed vedder anti sparkswitch (direct fet version). Feel like xt90 loop switches are the only safe option now.


What happened?

Was on the end of my route to my university, 5 mile trip, and on the last hill (15% grade), I got jerkiness from the motors. They lost power, regained power, lost power, regained power, that loop a few times, and finally lost it. Thanks to the v4 hummie hubs in 4WD, I can climb 20% grade hills even at over 30 mph. I was full throttling it up hill, made it half way, and this happened. Now the gate is stuck open, so the power switch is useless. It’s now just a hazard, cause it could cause this again, so I just removed it and have everything directly soldered. Till someone comes up with a solution, my board stays on 24/7, lol.

After spending years of developing these motors with hummie, I finally feel they can’t fail anymore and I haven’t had any failures so far in the few hundred miles I’ve done on them so far. My chaka quad vesc is rock solid, a few problems with caps falling off due to vibration (after 1500-2000 miles of use i’ll say), but that’s all in great working condition now.

Just when you think everythings solid, something will fuck up your day. I landed on my 3k laptop, so now I have to deal with that. All because of a stupid power switch.

This is the same reason I don’t like fuses in my circuits. They are another point of possible failure that I’ve personally seen friends eat it at 25+ mph. Simpler is safer…


Hmm, have you been braking at that moment or something?

I was neither accelerating or braking. I was at a constant 25-30 mph.

This is awsome :thumbsup:

Do you an idea of price point?

Something like 40-70€ I guess, will see with parts, I will be ordering some PCBs and parts for the prototype by the end of the week if everything goes well will try to make a batch of them.

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This design as is, won’t work.

there’s a few things that don’t seem right, but here is the most flagrant

you have no high current path on your ground, your tracks will blow at about 4-5A

Not sure what is U3, but if it’s a linear regulator, that thing will get hot to the point of failling.

-no gate protection, no current limiter. will make U1 fail if it’s a mcu

U1 is not mcu, u2 is mcu, u3 is high voltage low current linear regulator ~50mA its rated for 3x higher voltages so shouldn’t be a problem. I have already reconsidered ground plane.

The whole switching is based on high end BMS design

ah that is why you have two fets drain to drain. (edit patata potato)

so in this case Q1 is not doing anything, except potentially blocking any regen, it’s not contributing to switching the load. All the current will just go through it’s diode.

Wait what? They are not in series, they are back to back

It’s full switching so if its turned off no current goes in or out

I’d like some proven high Amp capable anti-spark switches. :pray: 100A cont. is minimum. 160A cont. would be nice too, I know some one else who would buy a few as well :wink:


I agree. Now that I can do higher amps since I’m not using a power switch, I’m gona try 160 amps and see what happens :stuck_out_tongue:

160a power switch would be nice. So would a bms though too…

The holly grail will be the bms + power switch, like j-tags bms. We need more though than just one option.

I will start working on BMS these days, I have already made balancer part now just need main controller + power switches.

For higher current rating I can put 2x or 3x mosfets but first I want to see how single performs

100A ill use as a pair… one for each esc, same as 160A

Hi guys, I just updated the design, went from LDO to buck converter the LDO did not provide enough current for simple led. Because of the increase in size, I went double Mosfet’s so it should be around ~200A but still, it’s in theory. The new board size is 30x50mm


200A is a great idea. If you want to future proof the design as 2 x VESC6 stock can do 200A (100A ea.).

If going by specs its 600A… But oh well…

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should be reliable then :thumbsup: