Capacitor spot welding energy storage cabinet

How to spot weld a capacitor?

Most spot welders use two points near each other or on each side of the workpiece. The current from the capacitor is probably just absorbed by the relatively large piece of metal. The second video below from [American Tech] shows a 500F capacitor doing spot welding with little more than two wires and it seems to work.

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.

Does a spot welder need a microcontroller?

This spot welder, unlike many available DIY projects, doesn't need a microcontroller to work: the welding pulse is triggered using relay module and a timing capacitor. Welding current is switched with an old recycled industrial thyristor module. Pulse energy can be adjusted with a potentiometer, which changes the voltage of capacitor bank.

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.

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.

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 This allows re-building battery packs for various devices, especially ones that are no longer maintained by the manufacturers.