Spot welding 18650 end-on-end (i.e. in a line, not parallel)

Probably the silliest question for a while, but is there an established way of spot-welding cells end to end, i.e. the serial junction of cells arranged in a coaxial line.

I was imagining that I’d put nickle tape across top of a pair while they stand upright and then just fold them creating a 180 degree bend in the tape. It seems like flexible stuff and its not like I’m going to be bending it back and forth. I’d do the parallel connections for the adjacent cells first I think.

Just figured I’d check in case either there is known to be a much better way, e.g. for joining cells in a line everyone uses copper braid rather than nickel tape because the stress in the bend increases resistance or creates hairline fractures which explode. Or maybe everyone just does the parallel connections in the normal way with tape and then joins those groups end on end with an external mechanical connection wedging the nickel strips up against each other.

All I can find on youtube are vids of people doing packs with all the cells parallel to each other as most are done by less space conscious ebikers.

Thanks in advance for any advise and apologies for what is probably a very silly question!

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If you’re going to try to fold the nickel strips, you’ll want to be extra sure that the cells are properly fixed to each other to prevent movement. I have a feeling that any looseness would snap the nickel strips over time due to road vibrations. I considered using this strategy for a while, but found it easier to keep the cells together going the other way, using hot glue in the space between cells. Has held up very well, and was very easy to build that way without having to use those silly plastic holders.

Good luck!

Thanks Alan!

One thing - I get that you provided mechanical stability with the hot glue, rather than relying on the nickel… but do you mean that:

  • You didn’t weld the electrical connections at all, i.e. the cells were just held in contact with each other by the glue and the terminals on each battery pressed together?
  • Or do you mean that you did weld them with nickel, but ALSO hot glued?

I figured I may no be describing it properly. I had our visualization dept knock up a photo realistic CGI of what I was thinking of, done in 3dmax and aftereffects. On left are two Q30s (texture was easier to reproduce accurately, luminescence a little simpler), then some nickel plate ready to be welded, then a DIY welder (again, cheaper for to render in terms of cloud resources), some welding effects (apologies if bump maps not realistic), then bottom left you see me folding them up, and the pair in final position in the bottom middle, and then a 4S3P pack bottom right so that you can see the parallel joints as well (shrink wrap was made transparent in that render.)


Relevant battery porn:

that last pic is there because its joining in on the fun, not because its welded like that.


Thanks! Much confidence this inspires!

Why not buy 18650 with tabs on them? I had an idea similar