I bought this pot welder from AliExpress for around 15 usd, it is a scary one but it works.
SEK 176.64 47％ Off | Spots Welding Machine Control Board 99 Gears Power 12V Adjustable Spot Welder DIY Kit For Welding 18650 26650 14650 Battery
https://a.aliexpress.com/_mOubbN6
