(Use science for peace please!) 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 in the 500 F range.
New TECNA 7913 - 415V Portable Hand Spot Welder Arms sold separately 6kVA (2 + 2mm Maximum Steel Thick TECNA TECNA 7913 - 415V Portable Hand Spot Welder Arms sold separately 6kVA 2 2mm Maximum Steel ...
As he notes in his writeup, the properties of copper which are most enticing, such as high thermal capacity, make welding it all that more difficult. His home-brew method of spot welding is ...