Custom li-ion pack ( turned out to be DIY spot-welder thread )

This topic was originally an request for custom buttery, it turned out to be DIY spot welder thread. You can view the original version of this post by opening the history.

Now back to the DIY spot welder.

I’ve designed a hardware and written the firmware for custom battery spot welder project. It’s cheap, compact and gets the job done.

Schematic & PCB: Firmware:

PCB design:

Right now, I have a working prototype on breadboard ( logic part ) & perfboard ( mosfets ). I’m planning to switch to the PCB I designed soon.

Shipping for dangerous goods will probably still be killer even inside of EU. You should make yourself a DIY Spotwelder and literally do it yourself.


This guy will do it and ship it, no problem :wink:

[email protected]

and you can use his calculator to now how much it will be! :

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Thank you very much for your helpful response.

You are welcome :smile:


a 10S4P battery costs ~280€ with that guy.

40 25Rs from cost 131€ shipped to slovakia. A DIY spot welder costs a maximum of 50€.

That would be 100€ cheaper than having it made plus you would have a spot welder for any additional builds in the future.

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Dont forget wires, nickel tabs, connectors. It can easily add up. I made that mistake lol

Je hezké tu vidět aspoň někoho ze Slovenska :slight_smile:

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Even the transformer would be more expensive than 50 euros :smiley: And then all the other parts, hours of work… yeah, not really worth it. Also, I don’t like doing things cheap-ass way, just so it works. If I make something, it has to be reliable, safe and reasonable quality.

And no, DIY is not always going to be cheaper. That’s a false economy. Sunko 709A looks like a good option for low-cost spot-welder. I can have it for 220€ shipped, but then… yeah. Already over 300 euros :slight_smile: I will also have to buy those nickel strips ( hard to find 0.3mm ) and so on. Gonna do some math and look for exact numbers. If the complete is 300 euros a DIY 350, it might be worth to spend 50 euros more and have spot welder.

Šikovné československé ručičky sa nájdu všade :slight_smile:

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You don’t know the Arduino Spot welder? It works with a 12V car battery - no need for a transformer. The parts are like 20€ plus some for the PCB if you want to make it right. There is no magic to do it right. My calculation was correct - I just built myself a 10S3P custom pack the same way. You also can buy the nickel strips from nkon - tgey are not 0.3 but 0.15 if I remember correctly but you can always just add layers with the spot welder. Personally I soldered copper wire on top of the welded strips.

Car battery is heavy and expensive thing ( 40+ eur, already over your 20 euros ). The charger for car battery is also not free. Then you have to get a pedal, also not cheap if you want it to be reasonable quality. I have a lot of wires at home, so that’s not an issue. Then there is MCU, which is like $1 or like $3 for the Arduino Nano. Electrodes ( huge copper pieces ), that are expensive ( at least where I live ) I can make PCBs at home, that’s not an issue for me, it’s almost free… Then you need mosfets and other crap. And even after that, it’s not even as good as a premade one.

What? You don’t have a car battery at home? You can literally use the one from a car. You don’t need a charger when you use a car battery. As electrodes you can simply use some 16sqmm copper wire - that should be easy to source. The Mosfets and diodes and stuff are ~20€. You can use any switch - I used a microswitch attached to the electrodes so I can trigger it with my finger: 2€. And according to the guys at endless sphere this DIY spot welder is better than 2000USD spot welders and can even be used to spot weld pure copper!

Id go the diy route here…

I don’t have a car :smiley: No need for it right now. Driving license is still on TODO list too :smiley:

But from what you guys say, I might consider making a spot welder after all…

but someone in your family should have one no? I don’t have my own car as well and just used the girlfriend’s for an hour. She wasn’t too happy but as long as the car works afterwards it’s fine :smiley:

go DIY especially because you’ll be proud of what you’ll achieve !

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@Maxid Yes, but noone will allow me to use their battery ( they think I’m gonna destroy it, lol ). The battery is ~40 euros, cheapest charger is like ~30 euros. There in Slovakia ( and Czech republic as well ) salaries suck compared to the rest of the world, but 60 euros for battery and charger really won’t kill my me :smiley: And I may recycle it in another project, so… :smiley:

@unikboards That’s why I do most of the stuff DIY :smiley: But sometimes it really isn’t worth it.

yeah ! fully agree. Great thing about what we are all doing is that it develops our creatitivy and commitment. I would say that DIY is a metaphor for life !

the skills that we learn, develop are really applicable in our day to day activities. never ever give up !

It’s a lifestyle!

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Pre-built arduino welders are available from here now:

All sold out but new ones will arrive around january 14th.