I bought MOSFET PCB for spot welding like this one - Link
Usually this board should be combined with LI-PO battery, but I have at home 1kw server power supply and I try to use it. However, the short protection kick at the moment I try to spot weld, and its turn off. Did someone try similar PS for this application and what you can recommend making it work? I was thinking to put battery pack in parallel, but I will need also charging circuit.
Add a big capacitor and charge it through current limiting resistor ......
I did calculate that 0,15Ohm resistor will limit the current to around 80A, but the heart dissipation will be 960W. This seams too much or did it wrong.
R = Resistance
E = Voltage
I = Amperage
P = Power
; RESISTOR VALUE
R = E / I
R = 12/80
R = 0.15 Ohms (I found this as standard resistor and 50W)
; SHORT CIRCUIT CURRENT
I = E / R
I = 12 / 0.15
I = 80
; SHORT CIRCUIT POWER DISSIPATION OF RESISTOR
P = (EE) / R
P = 12 12/ 0.15
P = 960W
1 ohm resistor max current 12A, check the charging time, you discharging a capacitor + 10A from power supply. Spot welding it is not a continuous process, you discharge capacitor with 1 or 2 sec brake.
Totally unsuitable for spot welding, you need current not voltage in buckets full. A capacitor discharged into the two electrodes sounds plausible but you need a capacitor that will handle a large amount of current without destroying itself.
The prameter you should look for is called the ripple current this has to be greater than the discharge current. Such capacitors are very large, expensive and hard to find.
I got the same issue with the capacitors. They are very expensive and not so popular, but I found that 3000F 2,7V Super capacitor can handle around 150-200A. Although it's not cheap, and I have to take at least 5 of them. I think I will try with some old car battery instead. They are much affordable and available.
[capacitir transformer spot welder - Bing video](https://www.bing.com/videos/search?q=capacitir++transformer+spot+welder&go=Search&qs=n&form=QBVR&sp=-1&pq=capacitir+transformer+spot+welder&sc=0-33&sk=&cvid=7E28A25E0F4F4484B6B6C55348D945F3)
3 kF? I doubt it. 
Hi,
I would to if it comes from bang or ali or ebay.
But Maxwell make them, not sure on the cost though.
https://www.maxwell.com/images/documents/K2Series_DS_1015370_5_20141104.pdf
Tom... 
This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.