FATboy anti-spark switch

FDBL86361 without heatsink can handle max ~ 30A/mosfet correct me if i am wrong - you have 2 layer pcb. with 2oz copper your traces could be max 30х0.07=2.1mm2. i doubt that 2.1mm2 copper will handle 200A current

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Who said I will not have a heatsink on the MOSFETs? The distance between wire (copper) and MOSFET input is small enough to handle this kind of currents, plus the MOSFET, and wire for 200A will also act as a heatsink for the heat transfer so as I say it theoretically after test runs I will be able to tell exactly it handles at which temperatures.

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Apologigizes dude. Your setup looks super promising I hope it comes together soon so I can get one :slight_smile:

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Alright so I’m confused. From what I can tell your using N-Channel MOSFET’s that switch the negative side of a circuit, so how are you connecting the positive rail to the MOSFET’S then?

What? Two minutes ago you said you switch the negative side not the positive

Sorry that messeg was to @pshaw changed message

So I’m still confused, are you switching the negative side of the circuit (low side) or the positive side (high side).

positive side (high side)

Yeah but how, your N Channel MOSFET’S source is connected to the positive input of the battery, how does that work?

It works as high side switch? Half bridges works the same

Ohh nevermind I was so confused lol was messing up my understanding of N-channels sorry man, thanks for your patience.

No problem I was prepared for more detailed answer :smiley: N-channel uses electrons to transfer current that’s why they are better situated for this kind of application but minus that you need to drive gate higher voltage than source, so you need bootstrapped gate driver, then P-channel uses holes which is not really efficient way of transferring but the easiest

@evoheyax Just curious …who made your switch ?

Golden Husky… Though I found another problem. My bluetooth module was causing some issues (sending a control signal it seemed like, which it shouldn’t be). Not sure if the power switch caused the bluetooth module to fail or vice versa. Will do more digging today.

aw shit now i’m scared my bluetooth is possessed

Well it is a risk I suppose. I’ve done hundreds of miles, probably closer to a thousand miles with my bluetooth module and never had an issue until now. Again, it’ll be important to get the whole pictures. All I know at this point is I was going up hill, got jitters, and power switch stayed on (wouldn’t turn off). I thought originally that the vesc’s weren’t getting power, but they were. Just the receiver wouldn’t turn on. I then noticed a buzzing sound coming from the vesc’s. I unplugged the bluetooth module, and that sound went away and receiver powered up. Power switch is still broken. Not sure if the bluetooth module is also broken or if it’s the VESC. I also notice at the same time, a busted capacitor (the big tube ones) on the master vesc.


  • Broken power switch
  • Possibly broken bluetooth module
  • Possibly broken vesc (unlikely, but possible)
  • Busted capacitor

This is going to be puzzle to solve though.

The bluetooth module is capable of interfering with the control signal (since they can send their own control signal while the ppm sends its normal control signal). That could cause jittering.

The power switch could of been opening and closing the mosfets (a short somewhere maybe), which could of caused the jittering.

The capacitor is a prime suspect of the jittering. If that blew, I would be left without enough capacitance, and the voltage would fluctuate under high load, like I was at the time.

Too many possibilities, but I’ll try to dig more see what I can rule out.

Check if components on switch has not micro breaks on solder joints because of vibrations

Guys I have a OT question but maybe close to switch subject. This BMS https://pl.aliexpress.com/item/12S-120A-version-D-lipo-lithium-Polymer-BMS-PCM-PCB-battery-protection-board-for-12-Packs/32799811707.html?spm=a2g17.search0104.3.80.KiDH80&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10151_10065_10344_10068_10345_10342_10343_10340_10171_10341_10541_10562_10084_10083_10304_10307_10301_10539_10312_10059_10313_10314_10534_10533_100031_10103_10073_10594_10557_10596_10595_10142_10107,searchweb201603_25,ppcSwitch_4&btsid=f93fe07b-7595-44f7-8e71-4c6b53f2c88f&algo_expid=d5e4b878-c9b7-47af-9c32-d901f527abb0-10&algo_pvid=d5e4b878-c9b7-47af-9c32-d901f527abb0&rmStoreLevelAB=3 has temperature switch. Can I hook up some standard switch and do you think it’s possible that will work this way?

@evoheyax for high amp loads you can run the vedder switches in parallel.

these are modified with 75v fets and when used with a 60 amp BMS they basically never blow at all. But when we went full discharge on Tattu lipo packs it was time to spread it around a little. Phoned a freind and we discussed how to wire this properly without draining the wrong drain. It works like a champ.