FatBoy Sparky Switch 300A 60V Anti-Spark Switch

Hi guys, today I would like to announce new project created by me (My father works on all mechanical ideas)

After reading a lot of discussions, a lot of shower thoughts and trials I finally created in my opinion perfect anti-spark switch for any variety load.


  • High Side Switching (Switches positive wires)
  • Push button (hold 0.5s to turn on / 3s to turn off)
  • Output for power indicator (will require resistor according to your selected led specs)
  • Single industrial size MOSFET in SOT-227 package
  • Ability to use any size of wires/bus bars


  • Up to 60V (14S)
  • 300A (MOSFET is rated up to 420A and impulses up to 1,000A) (200A constant limited by MOSFET leads)
  • Dimensions with screw and MOSFET is 16mm x 25mm x 45mm (2 x 18650)

For high currents, the heatsink will be required to be attached to MOSFET (Will have to research how much current can’t handle without a heatsink at normal case temperature)

Connecting diagram:

I do not provide fuse, as not all people would use 300A and etc, because decent 300A fuse cost a bit of money, so to save space and cost I am leaving it to the user.


Parts are already ordered, PCB will be ordered on Monday, so best guess around 1-3 weeks will be available to buy from our online store https://shop.3dservisas.eu


Finally an overbuilt antispark switch that hopefully might not fail


Does this have any safety features like push to turn on, but push-and-hold to turn off?

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At the moment I have decided these protections:

  • Turn on: hold switch for 0.5s
  • Turn off: hold switch for 3s

Any reason for the 60v cutoff? The ebike world could use this but up to 100v and same amp limit. Prices?

Switch control chip is limited to 65V I did not intended this for ebike’s

Ohhh I could put this through it’s paces on a 13s Evo Build, and if they work out well, maybe I can help distribute them in the USA.


this is great.

what do you think the price will be?

will it come with the push switch, or do we supply that as well? if the latter, is there a switch you’d recommend?

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About the price don’t know yet so can’t really promise anything but something around 50 eur mark

At the moment to make it release faster as people building projects for spring first batch will be only the PCB with MOSFET and screws.

You can use any switch/led as it require momentary push button (I would recommend those vandal switches as they look cool)

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I’ll take 1 for sure


I may pick one up :blush:

300a fuse is like 3$ malelectrics or whatever The place where you can get a spotwelder Its not much since they probably have like a 200% margain profit

Thanks for the link, I was looking at DigiKey for devent fuses with high voltage ratings, not 12V so maybe that’s why. But still first batch will be only PCB and MOSFET, later on we will provide with wiring and switch :slight_smile: But to make it faster will only sell first without them :wink:

Nice, why isn‘t the jst connector facing the other side?

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Great design! I finished my version of soft latching switch two days ago and ran into an issue which is common with the standard Vedder switches where if you are using the processor to pull the gate up or in another words have the gate connected to a pull up resistor to keep it from floating. I had this in one of the test versions and when connecting 4x2200uF capacitors simulating 4wd setup I found out that the high current for even less then 1ms when the capacitors are connected can charcoal the semiconductor inside the FETs which meant that it got stuck in closed state. I avoided that using pull down instead of pull up and software protection too so that the FETs dont get fried. Just curious if that is present or possible with these big FETs too.


@Nordle I used connector only for the holes, I will not be populating it to not increase the height of whole thing.

@Martinsp I am not connecting FET directly to MCU as I am using high side switching for that I am using gate driver. Regarding high capacitance load you need to control output voltage rise time in order prevent killing FET


Naaajs! Need to get payed now so I can order one or 2

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We received the PCB but there was a mistake made by me… Ground planes were disabled then I was generating gerbers… But for testing, it will be more than enough to see the performance of it.


After first turn on, with some light load of 10A it was working fine, next step is bit higher constant 80A don’t have yet higher current source available to test higher constant currents :wink:


Im sold if 80amp constant works out :slight_smile: