Simple Arduino-Based Spot Welder by GreatScott!

If you want to make custom battery packs out of 18650 cells, having a spot welder is an essential tool. Unfortunately, welders — and even kits — can be quite expensive. To try to reduce this cost, GreatScott! set out to make a simplified version, the results of which can be had for had for around 90 Euros, or about $100 US.

His device is surprisingly simple, and at its heart simply connects leads from a car battery rated at 300 CCA (cold cranking amps) or higher across a piece of metal to bind it to another. His adds control of the pulse time via an Arduino Pro Mini, which takes user input from a potentiometer, and displays pulse time on a tiny OLED screen.

The welder is activated via a fairly standard foot switch, which turns the welder on via an interrupt. The Arduino then uses a MOSFET and driver to control a massive electromagnetic disconnect switch, capable of passing along 1000A of current. The business ends of the unit are made out of nails soldered to heavy multi-strand wire to handle current flow.

While $100 is still not pocket change, it’s a reasonable price for such a unit, and it can weld .2 and .3mm quite well as shown in the video below: