I bought a new spot welder from Ali Express. The interface is bizarre, but the board is beefy and the spot welder is more than powerful enough for any spot welding job! The way it works is it does 3 pulses and the 3 segment settings control the three pulses.
Link to spot welder
https://s.click.aliexpress.com/e/_DFCWo9z
https://s.click.aliexpress.com/e/_DEKS3Jd
https://s.click.aliexpress.com/e/_DF3LWbD
https://amzn.to/3ZpeEpZ
Link to Lipo Battery
https://amzn.to/3wmNjUX
https://s.click.aliexpress.com/e/_DDmZmjZ