I took a sacrificial cell, .2mm nickel strip and pliers and ran lots of shear rip tests, I ended up higher like 50j on my build
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I also used 0.2mm nickel strips with Molicel P42A and Samsung 40T cells. For both I set energy between 48 and 50J. Welded with a Lipo@1200A. The first battery is from spring 21 and the welds still hold after the 3rd season. The chosen energy was based on tests and experience from someone who built several batteries with kweld. Definitely do some tests, I always order one or two spare cells for this purpose.
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Why choose negative?
The negative has contact to the jelly roll, but the positive is towards the vent, so if you blow a hole on the negative the cell is dead, on the positive it doesn’t matter so much.
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I took 22J for 0.15mm nickel and LG M50LT.
For 0.2mm I have 25J and for 0.3 I think it was 36J.
Of course, this can be different for you, so take it slowly.
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Honestly, no reason other than I find it easier.
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So same cells that I have. 
Just a general question to the forum:
I’m not clear about the amp range for each thickness and how much leeway there is for optimal performance and safety.
So far there have been three thickness options mentioned
0.15
0.20
0.30
I plan on 12S11P packs of the 50MLT cells. I purchased several never used 10S11P packs that were made for robots so after I remove the current packaging I end up with a lot of the welding work already done😀 I hope.
I hope to just add on 2S to those packs but I’m thinking perhaps I should ensure that I match the thickness of what is already done when I’m adding cells???
Again any help is appreciated
I would personally just use the same size that the packs already have.
I have tried to research all the amp rating stuff without much faith in the numbers. Hopefully someone smarter than me will chime in.
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Check @ludwig_bre cell connection heating calc sheet uploaded here, that’s the best effort i’ve seen.
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I finally found time to assemble my welder, Kcap and housings so that I could confirm that it’s fully operational.
I used a bench power supply set to 8.2V - 10A to charge the KCap. It took a few minutes before the welder “woke up” so that I could calibrate and try some test welds.
I did 4 welds to connect two strips of 0.15mm nickel 2 at 10J one at 15J and the last at 20J. They all seemed fairly solid but it’s clear that a 5J increment makes a difference in “penetration”
I then powered off the PS and did 15 more welds at 20J to try to “drain” the KCap. I stopped and let it sit for 30min or so and then tried a 16th weld and got an undercurrent error.
So successful test that confirmed that this is quality gear!!
I do have a use question though. If anyone is using the Kcap module how do you completely
drain the bank for long term storage?
Right now I can’t do any more welds but the led screen on the welder remains lit and the circuit board leds are still on indicating power remains in the Kcap bank.
How are these $25 welders from Aliexpress?
Don’t understand what your asking??
Sorry for being misunderstood.
I am asking - why buy Kweld instead of the cheaper alternatives?
I did my research and it appeared that lots of people that make quality battery packs use the Keen products and show that the quality of the welds are consistent.
Personally I have a philosophy when it comes to buying tools. Spend the $ upfront and get quality results even during the learning phase.
If I’m finished with the tool and won’t use it again I can usually sell it for almost what I paid for it.
Others might feel differently.
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Because Kweld works well and gives you consistent results. Good welds are crucial for a reliable battery. Personally, I wouldn’t want to use a crapy ali welder for expensive quality cels.
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That’s why I use an expensive welding machine from Ali - Glitter 801H
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WOW, that is expensive, x3 of Kweld.
Are you doing something special with it - like thick nickel ?
Or you enjoy the pedal?
Lithium Phosphate cells come with a bolt…
Nice. Power supply, cap bank and “welder” all in one.
Although the Keen product line is nice gear there is assembly required and the end result of three “modules” connected together is a bit ungainly.
Can you do rapid - in succession welds or do you have pause occasionally to let the bank “catch up”?
I don’t know why you think the 801D is three times MORE expensive than the Kweld- Kcap and appropriate power source is. Other way around from what I can tell.
I weld pure nickel 0.2, without pauses.
In the near future I want to try nickel-aluminum (NMC packages).
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