Spot Welder

I have been doing some research on making a spotwelder. It occured to me that some of the small spotwelders people make for Stainless Steel might be usable for welding battery terminals, even if not it would be useful on its own.

Two pretty interesting sites have plans using big transformers, with rewound secondaries to step down to 4vac.

5 bears plan

Another spot welder

This is a DIY battery tab welder. It is pretty nice, but I could not find caps as easily as I hoped.

There is some decent info on rewinding a microwave oven transformer. He uses 20 coils on the secondary to get ~36volts vs 5 bears who uses 5 coils from the picture to get ~4 volts . The 36v appears to be appropriate for a arc welder while 4volts with high amps is good for spot welding.


I have the basic plan of making something like the 5 bears site. I have a omicron solid state relay rated 30A 200-480VAC

A timer like the Crouzet PU2R1 might work

I am looking for a relay time to control the time cycle like the one 5 bears uses.

I think I can use a rewound microwave transformer I have like philpem uses.

I would like to use the power head to drive a manual spot welder, using conventional pinch welder tips, battery tab welder style, with foot switch, and possibly using it the welder as a dual tip (like the battery tab welder) to weld pieces setup on the cnc. It could be pretty interesting.