Calling Electrical Engineers: Can some please build a power switch that actually works?

You mean Fetcher design…

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I’ve been told to think of the fet as a gate. The more the gate is open, the more electricity comes through. And thus when you get your batteries full voltage through the power switch, the fet is open and electricity flows.

If I’m wrong, please correct me :slight_smile:

None of this is required if you get yourself a BMS with a precharge function.

Please explain to me what is a precharge function? My solution to balancing is simple: A balancing board. Let the switch turn the board off and on and the vesc’s to limit current and protect from under voltage.


Exactly what the VESC anti-spark switch is. The photo posted by ZackoryCramer 4 comments above this one is titled “inrush limiter”. The gist is it controls current over time such as 1 millisecond to prevent destroying sensitive electrical components. Now here the funny thing, an appropriately sized capacitor fits this category of controlling current that people in the RC community just use more capacitors and problem solved for preventing ESC destruction. But we have the electric skateboard with caps near ESC. The MOSFETs on the BMS does the job of controlling current output in the beginning.

Side note. On my setup, my BMS has this feature and I just use a 50 amp LP J Case Fuse. It sparks, but it’s contained within the case.

I understand you want an option as simple as a flick of the switch, but to increase the reliability of the circuit someone has to run a SPICE simulation to isolate the problem with the mosfet. The Zener diode, capacitor, and resistors are the least of your worry. I remember some post saying there is a specific type of Mosfet that can handle this Other than it being known as an N-Channel Mosfet.

Flick this switch…


AS150 antispark bullet…in a switch… its effectively a loop key you can’t loose…

PS it’s the size of one 18650…


Can we see how that fits into your board/build for design perspectives ?

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Don’t have it installed yet.

But you could just “add another cell” to your battery pack size and just attach it to the end of your battery, redesign the panel part of the switch so the hole is only as big as the switch opening. And basically have the antispark built into the battery with a mechanical slide underneath the bottom side of the enclosure.


From what I recall there is a voltage drop across the relay. Also you’ll need to find an alternative power supply to turn on and off the relay.

I bought one, then gave up and went back to XT90 antispark loopkey.

Post BOM! Post STL! Post schematic! =P Where’s the resistor that limits the current?

The saturation of the FETs is what limits the current as C1 charges up via R2

Oh, I thought you were talking about @ZackoryCramer’s schematic, sorry

Nope, talking about @Deckoz :slight_smile:

…With 5 Hours into the thread:

@Deckoz has a good design, but no details. @chuttney1 has stunned with his “just add more caps” observation and @ervinelin has disqualified solid state switches, and soooo…

@ZackoryCramer has the lead. Because he’s special =P

Can @Deckoz make a comeback? Will we ever solve the mystery of the faulty anti-spark switches? The thread is just getting started, folks!


So my 6s lipo spark inside my charger. So to stop that I just plug in 3s for a second then 6s.

Any way to precharge the caps with a lower voltage.

Adding more capacitance to the VESC will make it worse. Also, don’t add less…

Adding more capacitance to the antispark switch or upping the resistor value would increase the turn-on time, decreasing the current spike, increasing the longevity of the parts

Used both. No problems. 100 amps minimum though. Have had 40 amp units fail after a week.

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Was he was talking about more caps on the VESC…?

Can’t update the rankings until this is hashed-out… T_T

I use a bms and use the 6s voltage connection from the bms as the switching voltage for the SSR. Measuring with a DC ammeter measures less than 0.05 amps. Will measure again with a 4-20ma meter when I remember. No voltage drift in the pack as yet.

Can I know what do you mean you use the 6S voltage connection from BMS?

Use the 24 volts from the 6s wiring back to the BMS