Wow, X, nice to see you still around. Damn, i feel like a dinosaur. Yes, we all pretty much started with lipo batts. back in the day then we went to Lith batts. Thats what i was thinking, setup low voltage cutoff in the vesc tool to around 3.3, 3.4 so he doesn’t murdere the cells. Last thing he needs is to start a fire in his Marine Barracks 
. I don’t ride as much cause he was my riding partner, so i ride when he comes home, it still feels refreshing. I’m very much into Arrma rc trucks now and we use spektrum batts and charger cause they are smart batts and the chargers balance charges all the cells. Rc has come a long way these days with technology built into the batts. it’s so awesome. Anyway, thank you all for the help, its been a while but i really miss this place. 
. I’m gonna hang around now, great builds and technology also in esk8.
Aw shit it just clicked lol, i knew that name felt familiar 
The OG!
@kntzn moving this here to so people can chime in and others can see and learn too
I like to tin the nickel where im going to put wires if i can before i weld but its not a hard rule. The rule is to keep heat out of the cells as much as possible and this helps a lot to keep from having to heat it up too much. I also use something to heat sink the joint to cool it off and help prevent the heat from soaking all the way to the cells.
Start welding low and slowly increase until you get a good tear off. You want to see the weld leave little bits of nickel on the cell and pop holes in the nickel. Weld to get as much nickel surface area in contact with the cell as possible, it is debated but my opinion is that the weld is the fastening solution and not the only current path - surface area contact is also critical to making a good low resistance current path. So don’t cluster up the welds - spread them out to help hold the largest area onto nickel on the cells.
Also avoid the bullseye on the negative sides, there is a 3mm diameter area to avoid placing welds. I have started using my probe to make a small scratch or dent there to help keep my welds away from the center.
GOOD LUCK! Post up your attempts for some brutally honest but generally good natured feedback
Thank you for your reply
Unfortunately, transformer spotwelder failed to weld nickel properly. As far as I understand, pure nickel conducts better then nickel plated steel, so current required to weld pure nickel is way higher.
Increasing welding time leads to overheated nickel, and still no robust weld. It looks like transformer delivers more than enough energy, but at not enough current
P.S. test cell is dead
It seems like it’s a good time to give up and buy a pre-build welder. It is not so easy to find a kWeld here, so the question is will k99 be capable of doing a job of welding 0.2 pure nickel or i will have to use something beefier?
Thank you!
Try cutting a slit between the welds if you can. A Dremel cut off wheel might work. I have seen people have better luck - i think it helps to force the current through the weld instead of across the nickel.
There are some decent cheap welders, usually called red or purple welders. Look around on YouTube, i follow a guy Luca who has some good breakdowns and fixes for them to help make them very capable welders.
You can also try getting thinner nickel, .15 and .1 may do better with your current setup.
Also don’t neglect the power source you use. If you can get a good battery that can deliver more amperage faster it may help your setup perform better
Uhhhhh… I’m pretty sure you’ve got a dead short here buddy.
Nevermind, see below
Do not pass go do not collect 1000amps.
I’m not seeing it. It looks correct to me. Definitely quadruple check though.
Am I missing something? I even tried to check that his XTs were all the correct direction and they look like it to me.
Nope, I was the one missing something. Carry on.
Hell yeah! Go big or go home! (ground clearance be damned 
)
Planning to 3D print cell spacers for this abnormal cell configuration – sharing the middle like @glyphiks suggested.
For some reason my gut feels better about silicone wire for the series connections… braid could be lower-profile but jacketed wire feels more reliable and worth 2mm to me. Try to talk me into braid if you wish. I’m not too stubborn.
I literally got nervous for a split second 
But naw tt better be good i spent all day on it and did like five more diagrams just to make sure i got it. I did do some wiley shit to save some i dunno wire or space 
Ill connect some AAA batteries to it first 
Imho: these could be braid because they wont flex or move
These ones,
you can fold the nickel into a u shape and have the solder joints and wire on the forward/rearward face instead of the top surfaces. Will be a little trickier but the webbing of the enclosure should be below it. Then you get most of that wire space back and only have the braid in non flexible locations to keep it happy.
I have the K99 ‘purple’ spot welder, and can weld 0.1mm copper with 0.1 nickel plated steel on top.
The videos by Luca on you tube show how to improve this purple, and the ‘red’ welder, so it does not smoke the mosfets because the weld battery dropping to too low of a voltage during the weld.
Also, there is the potential inrush current issue frying a resistor or.diode which then fries the mosfets after a few times or sooner.
I did not do Luca’s modifications, but I do use a separate 12v battery with an xt90s, with the resistor, to power up the welder safely, but I use a separate Lipo weld battery.
Both battery (-) goto same (-) terminal on welder. The - welding probe is on the opposite end of welder. The positive from the non weld battery goes to welder, but the positive weld probe goes directly to weld battery +.
This basically eliminates the issue where the mosfet gates do not open and close properly due to the weld current lowering the input voltage.
The weld battery itself needs to be powerful enough to deliver the current required, as the welder itself is basically shorting that battery through weld probe tips, and the weaker the battery, the longer it needs to hold the battery shorted, which is hard on welder, and on the weld battery and unideal for many other reasons.
I’d like to use 0.15mm copper(or thicker), with 0.1 nickel plated steel sandwich on my next battery build. I believe my 3s 5.2ah ZEE lipo (Inexpensive) weld battery would be the limiting factor, especially now that it is now over a year old. I bet a higher quality, higher capacity, lower resistance weld Lipo would allow me to weld thicker copper nickel sandwich.
Make sure the ring terminal connections to the welder are good. the crimps and 10 awg they come with are of dubious quality.
I beefed up my weld probes to 8 awg, and try to keep Lipo.and its 12awg to xt 90s cool,for consistency, with a well aimed fan.
I need a 65 to 75 ms pulse to get a solid weld with 0.1 copper and.0.1 nickel plated steel on top.
I need about a 40 ms pulse to do 0.15mm pure nickel.
I have the red spot welder too. It proved weaker than the purple, all other factors being equal meaning same leads and weld battery.
Also, doing a bunch of test welds on a 0v test cell will lead to inconsistencies. A virgin cell with its nickel plating intact, is a different beast. If one is trying to weld atop.previius welds, or previius welds ground flat, the resistance is different amd will be inconsistent.
Also the amount.of pressure.out.on weld pen tips has huge effects kn the weld. Too much pressure is bad, as is too little.
And the shape.of the welding tips has a huge effect on the weld too.
Thank you for your suggestions
I’ve ordered alternative to those extrnal battery powered welders (red/purple ones) called A4 welder. I’ll try my luck with it, and according to reviews on YouTube, it should do the trick with 0.2.
That is why I practice my hands with dead cell, and going to tweak the current with spare “virgin” cells I’ve bought for that exact purpose - to test welds on the cells but do not ruin the pack
I’ve got a consistent result with slits on the nickel and the new welder. Does this seem right/owerpowered/underpowered?
It definitely takes some effort to tear it off.
Looks like a solid weld to me, the appearance of the weld can help indicate if it’s over hot or a miss fire but the tear off is everything in my opinion and that looks great
What makes me nervous is that I have to do more than 160 welds, and this
happens from time to time. Usually due to the accidental abnormal pressure on the tip or welding too close to positive tab edge, and this ends up with huge spark. Is it possible these welds will lead to a potential failure?
On the last pack i built, i accidently blew a hole in the negative terminal on a jp40 cell. I slipped a little when i went to push down with the electrodes. It was already glued in place too. That was no fun