So first unit welded up. Any thing look off before I finish the rest of them?
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Not recommended to spot weld on PCB - can end up ripping off the pads. Use solder instead.
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If the issue is the bus pads ripping off, wouldnt solder be the same?
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No, since solder attaches to a larger area and doesnât ruin the layer structure of the PCB. With spot welds youâre very likely to blast right through the thin copper layer and hit the substrate, thus weakening the surrounding copper adhesion to the substrate. This results in everything starting to peel off easier with external forces, such as vibration. If you solder the copper pads their adhesion to the underlaying layers (substrate) stays optimal.
Also, considering that spot welds(B) are actually tiny, they make a way weaker connection to the copper layer than solder(A) does. And now also consider the fact that you just most likely melted right through the PCB copper layer by spot welding. 
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Thanks for explaining further. Makes full sense.
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That does make a lot of sense however there is also the matter of how well you secure the pcb to the cells. If the cells are secure there wonât be any real stress on the nickle. I use a strip of strapping tape and hot glue. I inject the cavities and they come out as little bricks before any welding goes on. Iâve also figured out my machines settings to get a perfect weld without burning the pcb or lifting off the bus pad. Havenât had any issues with the batteries Iâve made so far. With a hard pull the nickle rips off the bus bar leaving holes the same size as the weld and the pcb underneath is not discolored enough to ruin overall integrity (slight yellowing). Iâll try and remember to post a picture next time I have a spare pcb laying about.
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Never underestimate the effects of extreme vibration. Even the little nickel piece going from the cell to the PCB is flexing - ever so slightly - but moving.
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@Makio13, I used solder on my kaly battery pcbâs when I made my pack recently however I believe that kaly spot welds the packs that he sells.
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Yeah, I had his kit laying around, so I was going to use it as is. But I may get more nickel and cross the bus on both ends.
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No experience to speak of here, but have researched quite a bit⌠But shouldnât the corners of the strip be rounded to eliminate any sharp edges that may damage insulation over time/vibration?
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Does this look right to you guys for a D140 BMS? Leads for B-, B1-B9, with B10 being eventually soldered to the main +
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What!
Jeez⌠#offended
#safespace
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that was a flirty gif
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Huh! Such a sexy flirt, I didnât know if I should have been offended or not, so, you know as a millennial, I know myself. Knowing myself, I know I should default to being offended. Thatâs just me.
Now thatâs all out of the way⌠
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These packs are looking awesome. Youâve done a super tidy job on these. However, i do wonder how good this method of construction is for the cells.
The idea with spot welding is to avoid subjecting the cells to the heat of soldering (although how much difference this makes is some what unknown). Iâm guessing the large (thermally conductive) copper bus bars need substantial heat applied to them to get good solder joints. This heat will quickly soak back into the cells as soon as the joint is made. At this point you might as well have just soldered to the cell because the spot welds are not doing much to help anything.
Honestly Iâm not sure how much effect this heat has. Everyone advises to spot welding over direct soldering but there are people who solder direct to cells and have no problems 
Iâm keen to hear others thoughts on this.
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There is no need for such strong connection between parallel cells in one group. current between them is really minimal. how do you plan to make series connections?
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Nice keeb.
If given the choice, Iâd always put the balance leads on the negative end of the P-pack. Just less chance for shorts. On the most-positive balance lead, you will need to use the main B+ or put it on the positive side.
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Can we get a list of the well known tools for battery making? Like the trusted sources for materials and the best spot welders for their price range
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