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Battery tag / tab welder from a camera flash Answered

About a year ago I found a project somewhere to turn an old camera flash into a spot welder for small batteries.

I found an old flash gun in my spares box and I wanted to have a go at building a spot welder from it but I can't find the weblink. Does anyone have any suggestions ?


All of the diy battery tab welders I have seen on the web use low voltage (15-20V) and high capacitance (over 1Farad). There is a big thread on Endless-sphere.com that goes through the building process for several versions.

I am working on a somewhat higher voltage version, but it will still have about 150,000uF of capacitors at 60V. If you charged a photoflash capacitor to 300V you could get the same energy with 6,000uF, but I was afraid that might also kill me. I do plan on making an Instructable once I get mine working.

IIRC  capacitance = voltage potential  whereas, to weld, one needs amperage.   For instance, my arc welder only uses house voltage (115 vac) but ramps up to 110 amps in order to weld.

You are correct that current causes heating. For battery tabs you want a short burst of high current so there won't be too much heat absorbed into the battery. Higher voltage means more current, while more capacitance means the pulse will last longer. But either way, you're putting the energy from the capacitor into the weld.

Well, to be more exact,   current through a resistance causes heating.   If one is using, say an arc to weld,  the resitance is the air space between the rod and the material being welded.

This one is awesome


Your saying you saw one somewhere that could do this with camera parts ?

I'm going to be looking very hard to find that.

You'd need more than just a camera flash. What searches have you tried so far?


Actually some of the bigger old flash guns might have caps that pack enough wallop for very small single shot spot welds...