Ordinary capacitors have a low energy density ... I did really need a spot welder though, and there was no shortage of examples of people who had built their own from supercapacitors, typically ...

His home-brew method of spot welding is admittedly quick and dirty, but it does get the job done quite well. He started off with an array of four 2.5V @ 2600 Farad ultra capacitors, which provide ...