K Weld - Power Source

Has anyone used a range of power sources with a k weld, such as a supercap+psu versus using a graphene lipo? The turnigy graphene 3s looks good, as kayak31 suggested.

The supercap is twice the price of a lipo, but it won’t overheat and go puffy like a lipo might. I like the small size of a lipo, but it seems wasteful if it only does a few cycles and gets damaged/hot/puffy. I’ve read that a good lipo will push more amps than a kcap.

I’ll be using 0.2mm nickel initially, as it seems 0.3mm is more difficult for k weld.

Another option , I just took my car battery the time to spot , plenty of power : set to 9ms

I use a car battery with my spot welder too.

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Sounds like I should pull the battery from my car and see how it goes, when I get a k weld.

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That’s what I did. Works great.

I’m using 2 5S 5Ah Lipos in paralel. It works fully OK but the XT90 contacts as well as the Kweld probes get quite hot after 50 welds. A 3min pause is usually required.
Usually weld 2 layers of 0,3 nickel and use about 70J welds on the second layer.

I setup my kweld with the car battery, and I was only getting 800A with the provided 1.1m long cables to the battery, making average welds. After reading the kweld manual about resistance calculations, I cut the battery leads down to 15cm each, with the kweld sitting on top of the car battery, and now it’s providing 1150A. :+1:

I tested with the 3d printed probe holder, and had some issues with sparking, which resulted in a couple of holes in test batteries - with one battery now leaking clear electrolyte. It seems difficult to keep both probes pressed flat with the holder, so I’ll try holding the probes individually next time. I’m concerned I might put a hole in one of my p42a cells, so will have to practice some more. Edit - it’s much easier to apply good pressure without the probe holder, for consistent welds.

I might eventually build a supercapacitor power source for the kweld. What would I need to put between the boost capacitors and the kweld, if I want to protect capacitors from inductive voltage spikes - some sort of TVS?

I used one layer of .02mm @ 15 to 20J. The neg end is much easier to burn thru so turn it down
Have you guys read this stuff?