What should my welds look like?

First time spot welder. Got the cheapest sunkko welder and it would not weld properly. So I got a bigger one, and it seems to blow out my welds a bit. If I use lower power they don’t stick. I’ve cleaned the electrodes, used firm pressure. And I just can’t get it to look as nice as some factory welds. 0922182033b 0922182033 0922182033a

I had it set too high at the beginning (left) and can get reliable welds toward the right. Replacing the batteries in a portable power bank that got left in a hot car too many times. Once I get confident I’ll move on to the 12s7p monster on my desk.

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FISH PAPER! I hear you scream. Well I experimented with some 3d printed rings. But they seem too thick and the nickle will have to bend pretty deeply. 0922182108

So I punched holes in fish paper. 0922182108a I’m going to quickly regret not finding pre cut stick on rings aren’t I?

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Please dont do this and get actual rings ><

If you make a mistake and make your holes too big, you could end up with an accidental short.

Do you have a source in europe for high quality fish paper, i only know that nkon has some…

Spot welds look burnt. Maybe spread the welds a bit more out and get rid of the sharp edges --> chamfer the strips!

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There’s a laser cutter at work, I’ll try and get some time on it and cut rings. Real fish paper seems hard to find, so I’ll just have to make rings with what I got.

As for burnt points, I’ll try spreading out the probes a bit. Don’t want to go over the edge of the terminal.

maximum pressure, and try to get minimum “brown area” and test your welds every one or two p packs if everything holds well

dude, you can get 200 of these for a dollar… with adhesive


Where? 10Char


even cheaper on aliexpress https://www.nkon.nl/accessories/heat-shrinks-insulation-paper/isolatiepapier-4x18650-top.html ok i guess 2$

How’s this? Got the settings dialed in and the fish paper cut out (didn’t take long with a hole punch and a printer) 0923181054

They don’t look consistent. Some hot …some not. Have you tried pulling them apart for strength test.

Please do not use that pack!

Remove all nickel strips, clean your cells, buy precut fish paper rings and adhesive fish paper. and start over, make 6 weld points (3 sunko discharges), protect all spots where the strips will touch the cells, use silicone wire to connect p-groups not nickel strips.

On every step take a picture and ask for forum members approval, don’t rush the job, the longer you take the safer you and your house will be.

No battery will be 100% safe ever, all we can do is to try to reduce the risk


i thought we use flat copper for the P connections…


Yes, they rip the strip before they break. Hot ones were me being new and getting too close to the edge.

It is real fish paper from Amazon. Did burn test and soaked resistance test. Each weld is 3 or more discharges and the strip rips before the welds break.

I can’t use copper bus bars as it’s a 7p and the vertical strips would come off the pack at an angle. I will be re enforcing the p groups with silicone wire and covering the balance wire strip with fishpaper.

Those welds are too deep. The metal is twisted and some welds are out of the positive button creating a most likely short. Please listen to eboosted and rebuild the whole thing.

Welds look no good. I wouldn’t even think about putting this underneath my board!