[Aaron Christophel] has a battery spot welder that costs a not unreasonable 30 euros and can also be used as a novelty power bank. He subjects it to a test and teardown in the video below the break.

The Power MIG 350MP multi-process wirefeeder/welder offers stick, TIG, MIG and flux-cored capabilities, as well as advanced welding processes such as Pulsed MIG, Pulse-On-Pulse and Power Mode.