Spot Welder

Sometimes it is great need to weld some metal sheets together. Sometimes they are very small, like nickel plated battery connectors. There are special industrial devices for spot welding, but for DIY and hobbyist user it is very easy to build this welder at home.

All you need is few very big capacitors, thick wire and DC power supply. Sometimes you need to put some resistance in such device, and automotive headlight lamp is very good alternative. The PSU must be as powerful as possible. Output voltage must be less than maximum voltage of capacitor and safe to handle.

point welder

Circuit diagram of the spot welder is something like this:

spot welder circuit diagram - schematics

In my experiment I used 3 capacitors 100 000µF at 16V each. It is recommended to use variable output power supply to change the welding power. Too much power may make holes in your battery pack. Before welding useful device make some practice on some bad cells.

Here is my experiment with steel tape-like detail from digital photo camera. It is about 0.25mm thickness nickel plated steel. Double spots made connection quite durable. Never use single spot- it tears of very easy. For battery packs prepare special nickel plated or pure nicker foil. As simple steel or copper will corrode in time.

point welder: some nickel plated steel

Magnified welding spots:

point welder: close up to spots

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8 Responses to Spot Welder

  1. Aali says:

    today i was looking for a diagram of spot welding then i saw your web page
    if you get my email would you please contact me to ask you more information about spot wire welder please

    regards aali

  2. garry says:

    Good day,
    pls show me a complete circuit diagram of a spot weld

    thank you very much

  3. This is Full circuit. Any PSU and these components. This spot welder is for welding small components- like battery cells. This is not welder for industry. Industry welder is a bit other configuration.

  4. Spot Welder says:

    Please share the video of how to use this diagram of spot welder.

  5. nero says:

    i want to learning from you. i saw circuit have a resistor on it ( R 1 ) ,so pls tell me what value resistor did you use ?

  6. The purpose of this resistor is to limit current from PSU to welding point and to limit capacitor charge current. This is very simpliefied circuit. In real world it is advised to disconnect PSU from cap battery during discharge. This spot welder is only for very tiny details welding: like attaching nicker foil to rechargable battery cell.

  7. Jorge Handajevsky says:

    Very interesting and congratulations. I would like to have a contact. Unfortunatly I couldn’t read the technical details. I’m interested in a welding equipment at 40 to 60 DC volts and this spot welder shown here seems to be the answer I was looking for.

  8. Iftikhar Ahmad says:

    R1 is a automobile bulb of voltage equal to source voltage.
    The capacitors are hard to find items.
    Reportedly 33000uf 16V capacitors work with a laptop 20 volt charger.

    In this setup when bulb extinguish means capacitors are charged and ready to
    spotweld. For next weld , wait until bulb extinguishes again.

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