why isn't there a "standard" design for spot welders?

[mindgames11]

I have a 99 gears spot welder that wont do anything over .1 thickness material- and sometimes even that rather poorly. I hate it and want something that operates at least marginally better, but the stuff at the lowest price bracket ($50, up from the $25 I paid for my board, not accounting the cost of the 5ah 4s 80c LIPO) looks to be so hit or miss in terms of reviews and of course they dont show what's inside their black plastic boxes so for all I know I could be buying the same board as what I have just with likely a much worse battery.

reading through comments (and looking at my and other boards) I see that a big issue with the commercial models is that they dont include gate drivers to save money (what an assed way to save like 30 cents).

In talking with chatgpt, I've come up with a rough design that basically is a MCU to control the weld pulse duration, mosfets, mosfet driver(s), TVS diodes, and an optocoupler. and nice big copper busbars connecting everything.

but whats confusing to me is why, with all this talk about spot welders and the deficiencies in the commercial boards, why isn't there a schematic stickied to this thread of basically what I'm looking to build?

 

[BatteryMooch]

but whats confusing to me is why, with all this talk about spot welders and the deficiencies in the commercial boards, why isn't there a schematic stickied to this thread of basically what I'm looking to build?

It sounds like you could be the first to post such a schematic!

Designing and debugging a high-current welder can easily take months and a decent chunk of money. Parasitic inductances and heating are guaranteed to vaporize a decent number of your prototypes, each requiring you to wait for a revised set of PCB’s to arrive. It‘s actually much easier and can be a lot less expensive to just buy a decent unit up front and use it successfully for years.

When I say “decent unit” I’m not talking about a couple hundred dollars. Reliability and functionality always comes at a price. But if you’re building a lot of packs then that cost, spread out over years, is nothing.

If you’re just looking to build a pack or two then you might end up on the same path as so many others…buying inexpensive units and hoping they can do the job without burning out. But I would love to see you develop a unit and post your progress here!

 

[sternwake]

Your 25$ / 99 gear' board sounds a lot like My first welder, which had a purple PCB and required a separate weld battery.

It was capable of welding 0.1mm copper under 0.1mm Nickel plated steel at ~gear 75 when the Zee 3s 5.2Ah lipo battery was new, but gear 95 when the battery had aged.

I spent considerable effort and time beefing up the welder, and using separate PCB and weld batteries, but when the Zee lipo started emitting the sickly sweet smell of electrolyte, I refused to buy another lipo just to have at best a welder which could not weld copper thicker than 0.1mm.

I now have an AwithZ P20B welder and am currently building a battery using 0.25mm copper under 0.1mm stainless steel, using the welding flux. It required gear 730( of 999) to weld this sandwich to a Murata VTC6. Testing the strength of this weld by rolling off the sandwich has deformed the Murata cell can far more than any other cell I have welded to, and I stopped before successfully removing the sandwich, and had to use some side cuts.

The cell is currently being discharged to zero volts and will be put with the others destined for proper disposal.

If you have the skills and time and desire to build a better PCB welder, by all means have at it, but you seem to be upset that a 25$ PCB could barely do what you expected of it, with seemingly little previous experience at spot welding batteries.

The Supercapacitor welder batteryhookup sells for 90$ seems to be well liked by those who have used one.

Ultimate DIY Super Capacitor Spot Welder

This is an amazing tool for the DIY community for building batteries. Reliable, professional, and built to last! Super Capacitor Spot Welder Instruction Manual Note: the last 2 photos show a holder that can be 3d printed. Huge thank you to Declan O'Hara for providing the 3d print file...

batteryhookup.com

If you already have a good USB-C supply, this is another fairly budget friendly option.

https://diy500amp.com/products/awithz-ukf10-1380a-10-2kw-super-farad-capacitor-spot-welder.

The Cheap PCB welders requiring their own weld battery are talked about at length by Luca, on Youtube.

I never performed any of his recommended modifications, I just used an XT90s for the Antispark hookup of Non weld 12v battery to PCB, and a separate Lipo 12v battery.
While I melted some traces, and bridged them with thicker copper, I never blew any mosfets of the purple board. The red welders I had fire shoot out of a Mosfet, and a black PCB welder I had it turn the electrodes into a machine gun and punctured the cell before I could remove the electrodes. I did buy a backup purple PCB, but never used it.

The battery you use on these welders has a huge effect on the power of the welder, and too powerful a battery can easily smoke them. Definitely a goldilocks zone weld battery is required. I tried 3 different cheap PCB welders. Only the purple one was any good in my experience, and it was not very good, not compared to the AwithZp20B anyway.