Is it safe to solder the cable onto the nickel after it has been welded to the cells?
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Pre glob on the nickel where the series connections will be. Spot weld the groups. Then go back and apply the series connections. Either way you’re putting heat to a cell. But with this way, you don’t have to put as much heat as you would with soldering everything after you weld.
Take a small piece of the nickel, put some scratches on it. Enough to expose the inner metal. Take a glass of water, add salt (I usually put 1-2 tsp). Put scratched nickel in glass and wait a few days. If you see any changes, it’s not 100% nickel.
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I’ve redone a 10s3p pack that only used nickel strips (except for main pos and neg output) into a 10s4p pack purely by soldering to the existing nickel strips. Didn’t have any issues with heat or the cells heating up while connecting everything together.
Can’t say much on the long term stability of that battery since I fried the BMS and ended up unbalancing all the cells again. I was fed up with it and haven’t touched it since as it had already taken weeks to balance all the cells previously. (no smart chargers or monitors so had to discharge with led based loads and then charge two groups at a time with a basic charger)
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… Multimeter or voltmeter, whichever you want to call it. 1s charge board. Live monitoring. Go fourth my son and balance them lol.
Have you seen said built batteries? Are there pictures/video of said built batteries being built? How are said built batteries holding up to the abuse PEVs can deliver? Find out what welder he’s using. These are all important questions you SHOULD be asking. Remember, you potentially have a bomb underneath you if something goes wrong.
If you haven’t @least skimmed through it, check this thread out.
That is because the welder in insufficient and likely junk.
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Don’t judge so quick. There’s always the possibility that the power source he uses isn’t strong enough.
But I concur lol
The cells are of questionable quality and aren’t really worth it currently. The battery wouldn’t last longer than 9 months at best 
I killed a battery with the same cell quality in just 6 months of daily use in 2021. The cells just didn’t have the capacity anymore.
Voltmeters are devices made only to measure voltage while multi-meters can do that and much more. There are also stand alone ammeters but no one seems to even remember them ever existing these days 
If I ever get into making my own batteries I might use the cells as practice for spot welding and put them together for a short lifespan battery. Since that is the one thing related to battery construction that I don’t already know how to do.
As it is now it takes up more space than needed due to all the extra padding and insulation layers I had to add to ensure that vibrations couldn’t create any shorts within the pack. So many layers of masking tape and fishpaper or whatever that green paper is called. Not worth it for even just a temp battery unless I put it together with new nickel strips
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I agree.
I use mine almost every day though.
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I have one of those clamp meters that is super handy when i need it, but i don’t need it often
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You might be right, it’s Chinese I belive. Cost a few hounder bucks. Unfortunately I don’t have other options and I’m already way way over the budget so it will have to do.
I was wrong, it a cheap aliexpress one for like 50 bucks. I get it today, I’ll post some specs and pics later
I’ve read the forum, but I’ll definitely do some practice on shitty cells.
I’ve never seen the packs themselves, but it’s working. My friend also repairs laptop batteries and such with the same welder. I know thats a different story but still, I have high hopes
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So this that’s that
I’ve asked around in local esk8 groups and friends but noone had a usable spot welder unfortunately so I’m stuck with this one
If you plan on building more than one battery, buy a reliable spot welder. Maletrics, kboss are my two favorites. As well as multiple forum member’s favorites. Maletrics will run you around $140 I believe. KBoss I’m not exactly sure on price currently but you’d have to find them pre-owned. Can’t recall if the they still produce them or not.
I had one of these and it died the second I plugged it in. Lol. Get something better.
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Soo
After some time I got my hands on a better spotwelder. This one’s chunky.
The guy who I got it from managed to weld .20mm nickel perfectly
I couldnt replicate the same result with 0.15mm nickel, here are some pics
Simply the nickel wont stick to the cell
Both are clean
Could it be that the electrodes are too far apart?
This is actually beneficial and not a detriment. What kind of welder is it? Did u ask ur friend what his settings were that allowed him to weld 0.2mm nickel? That’s where I’d start. Hard to help you without more info about ur welder.
I hope this doesn’t ring any bells but it’s a diy spotwelder, I don’t know how many amps, he said I should keep the amps nob on 99 and play with the time (1=20ms) and it worked for him at around 7-9
I was able to replicate some good welds with my stuff
Now my new question is, when spotwelding what counts as a good spotweld? If I tear off the nickel strip should it leave a small amount of nickel on the cell where the spotweld was, puncturing the strip or should it just come right off with some medium force applied and no residue, only some greyish spots