Capacitor instead of spark loop key?

The resistor size was actually discussed in the loop key thread you were referring to earlier. XT90s uses a 5.6 ohm resistor, but you’re not bound to use that value to make it work.

The “momentary push button then switch on” schematic I drew is probably possible, but not the easiest solution… Remember that all your current will go through that push button when riding your board, which means it needs to be amp-rated accordingly. It also needs to be vibration proof, so it doesn’t give continuous cut-outs and sparks… No good…

If you use the XT90S you don’t need to worry about the resistor as it’s included in the plug.

Here is the thing about antispark, its easy to build. I’ve did manual switch antispark system with double switch.

What cause the spark is the capacitor draining so much current directly from the battery. What does antispark does is limit the amount of current the capacitor takes with a resistor. You only need a resistor of 10ohm to do it.

So how does double switch mechanism work? the first switch is momentary switch with 100 ohm resistor, you trigger that (since there is a resistor), it doesn’t spark at all. It will take about 0.5 sec to fill the capacitor. After the capacitor is filled, you can trigger the primary switch (theres no spark), because the capacitor is already filled in and so there won’t be inrush current that will be pulled from the battery. This is the basic mechanism of an antispark system.

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I’ve thought a lot about That idea. To turn on less power hungry equipment like buck converters that would drain max 5A but still have an input cap. The thing is I have only found double switches that have each On position on either side of the Off. Ie. On-Off-On. Wich woulda be ok as long as you don’t get the sides mixed. Ideal would be an Off-On-On switch with the resistor on the centre On. That way flipping the switch from one side to the other would turn on whatsoever going first through the spark resistor. The thing is in not sure that kind of switch exists

Same. I used the anti-spark on a 13s battery and it instantly blew.

No this never be the case. It only blew if you turn the antispark switch system without connection the primary switch. So basically drawing so much amp through the resistor, ofc it blew. But if you use the antispark system just to fill in the capacitor charge and then switch on the primary switch, its no problem. Thats why its best to use momentary switch on the antispark switch so it will never blow.

Just realized how the double switch schematic should be done. duh…

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your problem would be the switch. just try to look up switches which can handle 50A+ and see how large they are

Well that’s about exactly what I said, and that’s why I suggest using a simple xt90s loop key.

@laurnts did use this on a previous build though and could probably share more about how his switch held up.

beside the switch issue, im pretty sure your last drawing wont work.

edit: attention > bullshit answer from me ahead :wink: you just created a paralel circuit and this way. you’d still get the spark in the main switch. your first drawing was actualy right (besides missing a capacitor to bridge the powerless once the tactile button is released)

no that schematic looks like it would work. Close the top one, then the bottom one. It’s exactly the same way that the xt-90s loopkey works

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ups, you are right. i kinda forgot that the spark is only created because there is no flow at all. also, i was still thinking about the “melting switch” problem ^^

while I was thinking about the melting witch problem

http://www.urbanbaby.com.au/WebRoot/Store/Shops/UrbanBaby/5255/FCE4/A4C2/645E/04DB/C0A8/DA0B/0725/BSWitchDetail.jpg

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This may be a dumb question, but the spark look key completely replaces an on/off switch, right?

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yes 100000chars

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The diagram is correct. I use the exact same diagram. Please note that what causes the spark is the instant draw of high amp by the capacitors. If the capacitors is fully charged (with an antispark), it won’t make the spark. The same exact reason if you plug the main (no antispark here), it will create huge spark. But if you unplug it for approx 0.5second and plug it back in, there won’t be a spark.

I agree that there is no small switch that can handle 50A, however I use DPST switch and make them work in parallel. Single line can handle 15A - 20A, so when it’s double it will hold 40A++. AGAIN, please don’t make such statement if you don’t know what are you dealing with especially about amp draws. I agree that there will be a moment that the switch needs to handle 40A up to 100A, but this draw only last not more than couple of seconds. So this switches will do just fine without melting down. I’ve ridden many times, uses the switches many times over the course of 2 years without any issues. Anyway if you’re so keen enough to look how much constant amp draw from the motor (use amp meter or vesc log), they only draw 1 - 3Amp constant and not 50A / 100A.

And let me tell you why there is no constant 50A draw like all member here are saying. Imagine you have 10s4p (36v 10Ah) in which the standard of batteries used by alot of members here. Say your motor draw 50A constant. Now convert that 10Ah (10 Amp Hours) into Amp seconds. 10 * 3600 = 36 000As. Now 3600 As / 50As = 720. You have 720 seconds = 12 minutes. Now question your self, does anyone here ride for about 12 minutes of rides with single or dual setup on full battery? I guess not… don’t be fooled by amps.

Your math is correct but it is extremely hard to read and your units are out of whack.

Hope you don’t mind me fixing it.

10Ah Battery (Amp*hour) 50A constant discharge (Amps)

10Ah/50A = 0.2h (Amp * hour / amp = hour) 0.2h * 60 = 12mins (hour to minutes conversion)

Yea I was doing it real quick, made some mistakes. But well this was explained alot multiple times, but i guess some newer member might have missed it.

Yep yep. I fully agree with you. I think it’s dumb for people to be building batteries that can do >100A continuous :slight_smile:

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people living int the alps or san francisco might disagree here :wink:

Sorry for the small questions, I’m trying to understand the discourse. The “instant draw of high amp by the capacitors” is referring to the V/ESC caps, right? Not some extra anti-spark control capacitor? If this is the case, would a sliding potentiometer that goes from a high resistance to zero resistance (assuming it could handle the amps I suppose) work?

Could you elaborate on your DPST switch? Do you use an arming button with it?