How do you Weld a capacitor?

Place one of the probes on the bottom metal piece & press the other probe on the top metal sheet. Some sparks will fly, after which you should see a secure weld nugget. Fully Discharge the capacitor after every weld.

Should I build my own capacitive discharge spot welder?

I decided to build my own capacitive discharge (CD) spot welder after being frustrated by the low quality and high cost of commercial units. Anyone building battery packs using cylindrical lithium batteries should, with some exceptions, be using a capacitive discharge spot welder.

Can supercapacitors be used in a spot welder?

Of course It certainly is possible to use supercapacitors in a spot welder, as I saw some existing designs, but they usually have precise pulse control with MOSFETs and microcontrollers, and these supercaps are treated in similar way as batteries. Regular electrolytic capacitors are easier to use without sophisticated pulse control system.

Can a spot welder use a Nichicon capacitor?

Currently this spot welder uses automotive grade Nichicon capacitors. It would be a good idea to check the feasibility of using cheaper capacitors, and test if it's better to use higher voltage ratings, or higher capacity. I managed to capture oscilloscope image of the pulse with an old analog Philips PM3226 oscilloscope.

Can a capacitive discharge spot welder be used to weld nickel strips?

In this project I designed and built a prototype of USB-C powered capacitive discharge spot welder. It can be used to weld nickel strips to battery packs. This allows re-building battery packs for various devices, especially ones that are no longer maintained by the manufacturers.

What power source does a spot welder use?

Other spot welders often use car batteries, microwave oven transformers, high-current li-po battery packs or supercapacitors as power source. All of these things seemed to be very powerful and somehow scary to me, so I decided to use an capacitor bank made of regular electrolytic capacitors.