It used to be hard to dump enough electricity through two pieces of metal to meld them together. But a lithium-ion battery can do it. The question is, should it? [The Signal Path] takes a cheap battery-based spot welder apart to see what’s inside and tries to answer that question. You can see the teardown in the video below.
The cheap welder has some obvious safety problems so the first thing was to trim down some wires and also retinning some of the PCB traces to ensure they are the lowest possible resistance. Of course, the less resistance in the wiring, the more current is available for welding.
The welder did do a good job securing a metal strip to a battery. After a successful weld, the video shows how to measure the current using a clamp-style ammeter with an inrush function. The resulting pulse was 960 amps, although it immediately drops over the 50 millisecond pulse, but still impressive.
The safety issues were worrisome, but easy enough to deal with and we’d suggest you do the same examination if you buy one. Some commenters mentioned that their version of similar welders didn’t have the same problems, but it is worth the effort to check before you burn your shop down.