LOL, yeah, it's kind of the US. The link you had, had a bunch of UK posters and I didn't look closely enough to recognize they weren't your posts. That is an ambitious project. I was considering doing an EV, but figured I'd start simpler with a bike when I get the Powerwall thing done. Too many projects, too little time.
Have you tried it? The 4.2 V li-poly based I have tried are too low voltage to give enough current. This one is 5-5.4 V, so about (5.4/4.2)^2= 65 % better due to U^2/R=P. kWeld is much higher at 8 V with the capacitor kit. This being my third spot welder, I'm thinking if I should stop playing around, bite the bullet and buy the kWeld+capacitor bank or try to save about 120 € off the 300 € kWeld+kCap.
'Scuse my ignorance, but what is MOT in this context?
Microwave oven transformer. If you search for it on YouTube, you'll see several dozen variations on how to make one. Pros and cons to everything as always, and Kwelds or purpose-made spot welders are certainly better in a lot of areas. But the main appeal to MOT spot welders is that you can make them very cheaply using scrap, which is a big plus in my book; i spend less than $20 on mine, and its far from perfect, but it gets the job done. I've made thousands of welds that have held up, including on my DIY e-moto that hits potholes on a daily basis, and the battery is still just fine.
Any recommendations as to which is a good one out of he several dozen?
I did it two years ago, so I can't pick out a specific video. In addition, my advice is to watch 10 at random, and pick out the details that you like the most, that work best with your parts. All the videos have different noise-to-content ratios.
An arc welder is a transformer already. It's just a different size and current rating then what's in a microwave. But you're not wrong, a transformer is a transformer, it's totally possible to use one from an arc welder. You'll just need to test out the correct windings to use.
My thinking is that an arc welder is already set up to deliver loads of amps: that bit shouldn't need messing with.
Maybe, but it depends on how much. Estimated figures off the top of my head, I believe that arc welders are in the range for 100-300 amps, at 10-30 volts. For spot welding batteries, you're looking at 600-800 amps, in the range of 1-3 volts. Settings will vary. So an arc welder unmodified it's going to work on a battery, in fact it may risk blowing a hole in the thin casing.
Well that's confused me: the control board you linked to earlier comes in 40A and 100A versions.
I believe my multimeter and ammeter readings more than the online ratings of Chinese electronics. But if you're asking, none of my beliefs are firmly held; I've learned too much in the past few years to think that I'm right about anything!
No, you're not missing anything important. Spot welding is low voltage, high amps, short time. There's more than one recipe to get there. You should mock up a system using what you have to see if it works, and go from there. Do you have a few dozen useless and discharged 18650s that you can practice on?
