Li-Ion spot welder

Almost two years ago I decided to build spot welder for batteries. After researching my options I choose construction by Albert van Dalen

https://www.avdweb.nl/popular/spotwelder/spot-welder-controller-building-kit

It is microwave transformer based, controlled by arduino. It switches primary side with two big-ass thyristors. It also does peak detection of sine wave, to turn on welding exactly when phase voltage is highest. It uses double pulse method. Read his article. I think this is best free construction you can build.

I bought Sunkko welding tweezers. But those are crap. I dissembled them and created two independent swing arms. Arms are long enough for very big battery. Pushing force is adjusted by hand. There is a pedal input to keep both hands for welding.

I measured current trough secondary side with Rogowski probe. It was not during welding, but output was connected firmly together. Over 1200A, nice 🙂

And here is some examples of batteries made with this one:

And this one is done with my spot welder by friend of mine whom I borrowed it.

7 thoughts on “Li-Ion spot welder

  1. UMA

    This is an excellent article. I like this topic. This site has many advantages. I have found a lot of interesting things on this site. It helps me in so many ways. Thanks for posting this again

    Reply
  2. Morlan Liu

    I’m building a similar spot welder using two 1000W 120V microwave transformers connected in parallel using 3/0 AWG wire for the secondaries (two turns) and getting ~2V open circuit.

    Can you tell me your open circuit voltage and whether I should connect in series for higher voltage but less current?

    Have you spot welder 0.2mm pure nickel strip? If so, what pulse width and current do you recommend?

    Thanks for your help!

    Reply
    1. mirek Post author

      Hi. I have like 3 turns of 35mm^2 cable and it is too few. I have also something like 2V open circuit. I 0.3mm nickel strip is too much. Strip of 0.15mm is a max for my welder. But I do not have exactly great cables to electrodes. If you can, use one more more turn. For welding times I am not sure. It uses electronics and firmware from https://www.avdweb.nl/popular/spotwelder/diy-spot-welder I do not remember exactly how long it welds for different settings.

      Reply

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