I can little english… 
The thin copper wire will act as a fuse.
The reason for the broken wiring of the PCB is the same.
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Probably. I think you are pushing it.But that depends on your battery. With my battery setup 8 is too high. With yours maybe you need more than 10. Also I was welding 0.1 and you are welding 0.13 you need more than me Make sure: You have your lipo fully charged Points polished Good contact Good cooling on the fets Good pressure I’d try a thinner tab and another lipo. I guess you can borrow it. In case your lipo is new and top quality forget about the lipo advice.
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Yes I told you it sux. Sorry but I have no time lately for videos. Download it and watch it with vlc player. It has a 200% volume pump
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Mod it with fans and heatsinks if your temperature rises too much. The fets must be under 50° celsius
The way I’ve been thinking about this… Normally parallel connections carry very little current, so just about anything works.
Series connections carry full current. If using 30q and you want full power, each cell’s series connection should be able to handle 20a for at least a few seconds at a time. It seems 10mm x .2mm is almost okay for one cell’s power.
So, if 4p, I’m thinking each cell gets a series connection to the next group, 4 strips. This is good for the foldable part of the pack, but if connections are going across the tops (or bottoms) of the cells, need to add some serious copper.
I’m thinking you want more copper than the 4 x 20a would mandate, because since you make the connection at the first or last cell, you have some non-zero resistance as you go across the parallel group, leading to uneven load sharing in the group. So minimizing this resistance will help with load sharing.
Someone please tell me I’m overthinking this!
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i’m making a single layer pack and all the connection are part of the same chain and the parallel connections are using the same strip as the series, and there’s uneven load sharing. A giant serpentine path. its not an ideal way to do it electrically but if you have a diagram of a single layer pack with better I’d like to see it before tonight when I’m going for it.
come to find what I think the danger is with copper and gloves aren’t gunna solve it. You can more easily blow a hole in a cell with the high power and possibly not know it and have a hole in your pack. I was practicing on a cell I know had a hole and it went what I guess would be “runaway”. Not a fire but too hot to hold.
i’ll put more lipos in parallel to see if I can then put in a lower “ms”
So I removed the upper PCB by desoldering the 6 pins of connection with the middle PCB . I used desoldering braid.
As you can see in the photo there is a PCB track that burned and it’s broken. This track is used for powering the arduino, and as I was told, the track serves as a fuse to protect the arduino.
As I’m not sure what caused the problem, I decided to put a conventional fuse (1A) to protect the arduino and be able to replace it easily without having to restart everything.
The arduino restarts 
, but I have not tested the spot welding part with this assembly.
Wait & see.
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Please take a pic of the reverse to let us see the final position of the fuse. Share with us the results of the repair. Thank you
Good!!! I am wondering how to work more comfortably. I will modify PCB.
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Yesterday I got to try my spot welder with a couple of discarded 18650 and the included strip. This thing is simply incredible in its size. Second spot And I can’t pull it off. Congratulations @aulakiria
I got mine within a week and built a pack with .2 nickel strips and it worked great! Very easy to use… Also, I did a corrosion test(water/salt, vinegar/salt) on the strips that came with it and they passed. Although, I didn’t use them, because they were too thin for my project.
I must be cursed with this spot welder. Following my previous repair, I started assembling my pack. Visibly there must have been a short circuit at the time of the welding, I had briefly a “FET error” then the fuse that I had installed jumped. I think this time I will have a hard time finding a solution.
The god of the esk8 is definitely not with me right now … 
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Spot welding position is wrong.
Both tips should be placed on the center positive terminal.
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The positive button must be taken carefully. If you have one of the points on thin air you got a guaranteed hole. You must aim at the centre of the circle. Everything around that circle is negative so shorts are very easy to do. Just by looking at the pic seems you aimed to the edge. Repair those electrodes. Make sure they are insulated from each other. Seems the shrink has been damaged. And the copper darkened. Rub the points gently on a sand paper and use some shrink tube if needed. The short must take place on the nickel not on the points.
Thanks, i know i misplaced the spot welder. The problem is not the electrode (i can repair it), the problem il that it broke the velder (i have now another short circuit on the PCB, and possibly a FET problem …).
Lee i’ve sent you an email 
Thanks Rojito
@aulakiria : Maybe it could be interesting to improve your design by adding some protections: a fuse for arduino, a circuit protection to increase robustness of the spot velder in case of this shortcut type …
I don’t know if it’s possible technically:face_with_monocle:
Does anybody know the maximum width of strip you can fit on those black plastic 18650 spacers?? That would be the distance In red
I got some of Those. But I am not at home. Maybe I can tell you later.
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