Will i have too little current for weld ?

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bikermice

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Jan 8, 2014
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Hi guys.
I want to build a spot welder such as this

I want to replace the battery with a 12v PSU and capacitor bank.

i need some help.
I have 9 10000 uf capacitors connected in parallel connected to a 1000 ohm resistor .

If i charge it with a 12v 67 amp power supply. Will the discharge be too little or too much for spot welding 18650 cells.
The idea is to replace a 340 amperage 12v battery with the above mentioned capacitor bank. And use a button switch and a 80-150 amp solenoid for the trigger.

If you look at the welder in the youtube link it produces spotwelds just right using a 340 amp 12v lead acid battery.

The idea is to replace a 340 amperage 12v battery with the above mentioned capacitor bank. And use a button switch and a 80-150 amp solenoid for the trigger.
 
Last edited:
No, if you entered the values correctly, you only have .09 farads in total. A 1 uf is .000001 farad so 10000uf is ,01 farad. Supercapacitor welders use 600-1000 farads. maybe more.

Not many people still use a solenoid to trigger a weld these days. Electronics have replaced the fast finger. Seems like 90% of the low cost electronics they sell out of China blows up though or is too low power to build batteries for big ebikes,
 
So what does this mean the capacitor bank i have is too weak ?

I have seen capacitors this size melt nuts together... i just need to spot weld 18650s.

How should i configure the cap bank then ?
 
Ok this is a parralel connection yes ?

The spotwelds seem a bit overpowered but it
obviously does work.

All want to know is if i put a 150 amp starter solenoid on my 9 cap 100v 10 000uf cap bank with a switch using a 12v psu to charge the bank. Will my welds be better than the above link.
 
No! You're using the wrong caps and they won't store enough energy. Though you can build what you propose and see for yourself how well it will work. No need to argue.
 
How many joules does it take to make the kind of weld you need?

www.omnicalculator.com

Capacitor Energy Calculator

Check this capacitor energy calculator to find the energy and electric charge values stored in a capacitor.
www.omnicalculator.com www.omnicalculator.com
shows that 12v 0.09F provides only 6.48joules.

That's a total that takes time to get out. The time to discharge the caps is the same as the time to charge them (if the reistance is the same) so the calculator below will tell you how long it will take to discharge (and so how much of that above energy will be applied to the weld for a given time),
www.omnicalculator.com

Capacitor Charge Time Calculator

Calculate the charge time of your capacitor for the five multiples of the time constant and more.
www.omnicalculator.com www.omnicalculator.com
So you can use that once you know the total resistance of your capacitors, welding leads, material being welded, contact resistnace between the two, and all the wiring involved.
Then you can also figure out how much current you'll get.
 
OK i want to believe what you saying but why does this guy's setup work with normal caps ?

 
bananu7 said:
For some definitions of "work". He's dumping tons of heat into the material during what he calls "welding". You could use a regular soldering iron and be quicker than this.
Click to expand...
I hear what you say. I want to use a solenoid with a switch connected to the cap bank i mentioned above. I know a solenoid setup is not the best solution but its what i can get locally.
 
In that last video, he is using 200 volts to do one weld. That is danger zone. That much capacitance and voltage will kill you, It will also explode your lithium battery. You have to have some respect for what we're doing here.
 
docw009 said:
In that last video, he is using 200 volts to do one weld. That is danger zone. That much capacitance and voltage will kill you, It will also explode your lithium battery. You have to have some respect for what we're doing here.
Click to expand...
Ok so if it releases so much energy as you've seen in the video, will nine 100v 10 000 uf capacitors in parralel not produce enough discharge on a 12v charge ?

How about if i charge it to 24 or 48v ?
 
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