[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.

[Mike Worth] wanted the option to run his Microwave Oven Transformer welding rig at less that full power. After being inspired ... some wood shielding over the coils and fired it up.