Yes, the wrapped pack is coming apart. I cut out just one section of a positive end and the strip popped right off with just a bit of nudge. Dammit. I might have better luck with some 0.12 nickel strip I have… might do that and stack a few layers on the main ends.
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Couple of weld pull tests can go a long way to preventing annoying rework.
hmm no point in me saying this now really sorry haha. Been there is what I meant I guess
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ok, everyone’s naked again. Going to start over.
It was weird, almost all positive end strips came off easily and most of the negative ends were stuck ok. Either way, better to clean all of them off and re-do properly.
What does nickel like more, shiny smooth surface or rough sanded one?
No reason to rough it up for spot welding, only for soldering.
I think the roll of nickel strip I used initially was crap.
This time I used the 0.15 one that came with the welder a while ago and it stuck on much easier. For now all the parallel pairs are connected, going to make the series connections tomorrow.
Help me understand how much nickel I’m going to need for the series connections.
The strips will be short with my cell layout, a few cm between each parallel pair. If I plan to draw 30-40A at most, does each series connection need to be able to handle that? Does that mean I would need to stack at least 4 strips of 0.15x8mm between each cell pairs for the series connection?
Did you test it to make sure it’s not nickel plated steel?
Scratch it and put in salt water, it shouldn’t rust.
Yea, I would say 3-4 strips; but I have a feeling at some point stacking becomes counter productive and might not increase your ampacity linearly. Plus, more spot welds = more things to fail.
Don’t have experience with that myself, I always use wide 0.2 nickel with a good spot welder.
Cheap or good, you have to pick one 
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Good idea. I’ll do this with pieces from both batches I have. How long would it need to stay in salt water?
Overnight, but if it’s steel, you’ll see rust much sooner.
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The switch function just enables/disables the charge/discharge IO. I was hoping for something that completely turns everything off, including the bluetooth. The good news is that there is no LED’s that are always on.
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Long day.
I ended up stacking 3 layers for the series connections. For the main leads I welded one end of a stack of 3 strips, soldered the wires and then welded each layer one by one to the first/last cell groups.
Happy to be done with this pack, especially with having half of it basically re-built. What should’ve taken one afternoon, ended up a 4 day quest.
Everything seems in order so far but the conclusion will be tomorrow when we connect the BMS for the first time.
Also, it fits in the box but it’s a bit more tight than I would’ve liked. Not going to print another one, but there’s no more room for foam tape or any sort of vibration insulation in there.
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You can try using some butyl tape as a gasket to add some waterproofing and extra clearance for padding
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Solid.
It’s been almost 24 hours. Quite unexpected results. I can see just a tiny bit of corrosion on the “good” one.
The one on the right works much better with my welder.
The one on the left which is still completely clean, I was having trouble getting it to stick to the positive ends of these cells. Likely the welder is just not powerful enough.
It’s strange, I don’t think it’s coated steel, there’s just too little corrosion. Maybe nickel but with lower %?
Either way, I used up almost all of the stock with this pack so I’ll be looking for another source soon.
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It’s alive!
The BMS app connected right away, no issues there. It does have a lot of settings so I’ll need to do some research. Not sure what I need to set up in there so it does what I need - balance.
Is there a way to set it to balance the cells all the time, not just while charging? Should it do that?
It did ask about the pack capacity on the first start up, which with my 12s2p setup should be 30Ah (198Wh).
This is what it shows. Not sure why different colors for cells and I haven’t connected the charge port yet to see how that works.
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Kudos on your designs for additive manufacturing, i saw you had the floating holes trick applied too! 
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Thank you! Indeed, I learned about this when I built the Voron.
I think I didn’t connect something with the BMS. It won’t charge. I just connected the main battery + and the C- from the BMS tot the charge port and nothing happens… hmmm…
It should work, on all the drawings this is what I saw, C- and pack + to the charge port.
Is there a setting to change to enable charging? It’s the boosted 43.2v brick I’m trying to use. It does output that.
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is your charge port open in the app?
good question, how do I find that? This is the android app I’m using, I read that some settings might be missing from here
Edit: you mean the “charging” button slider on the main dashboard? Yes, it’s green, should be on, see the screenshot above… or there’s another setting?
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google overkill solar, its a better fork of the software. it should be one of the slide bars in there on the top.
