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cheap spot welder, moddable?


10 kW
May 11, 2015
i purchased a spot welder the other day, this thing

came with some 0.2mm thick nickel strip, spot welds it fine to 18650s (on the max setting)

however, i have some 0.3mm nickle strip and it doesnt weld that properly, very loose attachment and it peels off easy.

couple of questions.

1. is the thicker strip not welding due to lack of power or quality of strip material?

2. if its a lack of power, can these welders be modified? (atm it has a 1s battery, would a 2s help or blow it up?)

thanks in advance
I would recommend that you investigate the copper/nickel sandwich method. Copper conducts so well that it doesn't build up much heat to cause the spot-weld. Nickel has a lot of resistance, and it is only common in mass-produced batteries because its easy for robots to weld it rapidly. Nickel is a poor conductor.

Going to thicker nickel is problematic, and its is easier to use a copper strip on the call, and a nickel cap over it. Since copper is four times more conductive than nickel, a 0.10mm thick copper strip is as conductive as a 0.40mm nickel strip. Try 0.10mm copper and also 015mm copper.

For the spot-welding cap, 0.10 nickel should work fine, but 0.10mm steel might work better, and possibly be cheaper. Since steel is subject to corrosion, the nickel-plated steel that we used to hate is actually an awesome spot-welding cap.

For anyone in harsh environments who is worried about the copper corroding, there is nickel-plated copper available now.

One mod that you can do is probably use thicker gauge wires for the probes. When you do your welding do the probe cables jump around as you do the welds and get very hot? that would be sign the cables are too thin.
I have a larger 12 volt malectrics spot welder and when I first got It, I was using 8 gauge copper clad cables (speaker wire) and wasn't too happy with its performance, I had to use high power settings to get good welds, and I could only do about 10 welds at a time due to the cables getting too hot to hold. I decided to replace the cables with 6 gauge pure copper (welding cables) and that fix my problem, I was able to reduce the power settings and could spot weld all day without the cables heating up.
I wouldnt add more batteries (2s) on the cheaper spotwelders. I had a 40 dollars welder that I had bought as a backup and it didnt last too long maybe 5 welds before it shorted out from too much power.
With the thicker gauge cables, you get more amps to the tip of the probes at lower power settings, at higher power settings it might be just enough to do what you want to do.

This is a picture of the 6 gauge pure copper cables I'm using. I'm using copper nails as the probe tips. This has worked excellent on my spotwelder and have done hundreds of welds.

a 6 gauge probes.jpg
I was looking into these before I decided that battery building is a bit beyond my danger zone. With these portable spot welders, don’t press too hard. Just enough to make contact and the arc will do the rest. Have you tried to weld with different pressures? Might be worth a shot, since it won’t cost much.
thanks for the advice.... my leads are 8 gague and do get warm (not hot) after a few welds. i will look into making them 6 guage.
ha lol, i guess i should of read the page before i bought it.... does upto 0.2mm nickel strip and 0.15mm stainless steel. with a capable unit costing about the same as some 6awg cable.....i might just go for a new unit.
I would recommend you buy one without the battery (or just replace the battery in that one) since that is probably the limiting factor in how it actually performs, most of the resistance is in the battery. You of course have to source a suitable battery but then you can get one with a low enough IR to do what you need. The limiting factor after that will probably be how long it lasts until you blow up the FETs due to voltage spikes since these units seem to have zero protection. I have one of the cheap aliexpress specials and the first thing I did was add some copper to the PCB traces (probably the 2nd largest source of resistance) and some protection diodes and TVSs. Also make sure to keep the cables far away from each other and as short as possible to reduce the voltage spikes and resistance of course.
yeah, im getting that feeling too.

ive just added some 10awg (biggest i have) to the leads in parrallel and it's gotten better, but still not good enough.

adding some solder/copper to the traces is a good shout but i half feel it still wont be enough (will try).

between adding a 2s to this or geting a new unit (minus the battery) i think ill get a new unit.

i would imagine as the thing i have is only 1s and usb-c charged. that a 2s or 3s wouldnt play nice with it.
at least worst it wont charge through usb, at most worst itll just blow up the control board side and defunct the unit.
The maletrics (version 1) I got about 4 years ago I paid 90 dollars for it. It has worked good. I had to buy my own 6 gauge cables (about 20 dollars) . It was an expensive purchase but I had to spot weld the nickle strip since the soldering wouldn't stick to the lifepo4 cells I was building. The spot welder did quick work of building the battery and have spot welded all my batteries since that time.
I checked the maletric website and they are up to version 4 and on the FAQ it states that it can do nickle strip 0.3 thick. The version 4 spot welder can use either a 3s lipo or a 12 volt lead acid start battery.
I wouldn't recommend any of the cheaper spot welders, the only one I tried was a disappointment. I also don't recommend the plug in spot welders which require too much house current to work.

This is a picture of my maletric spotwelder with the handmade case I made for it, its not pretty to look at, but it is a reliable workhorse. I use this to build a 220ah lifepo4 battery bank (160x 36650 lifepo4 cells) . It was cost effective for me, the cells including the spot welder cost me about 500 dollars. Cheaper than buying even a 100ah lifepo4 prebuilt.
malectrics probes.jpg