Harvesting 18650 cells from 4-cell (2S2P) Cable Modem Batteries

Working through 200 4-cell cable modem batteries for the power wall.

Working with lithium ion batteries is inherently dangerous. Be sure you are experienced at doing this kind of work and take adequate safety precautions before attempting this yourself. The techniques illustrated in this video are for entertainment purposes only. No doubt, there are many other equally good ways of opening these battery packs. I used what worked for me with the tools I had on hand.

There are likely several ways to open these packs. I found this technique worked best for me. It was fast and involved no cutting with sharp blades. I experienced no cell damage in opening hundreds of these packs using this technique, YMMV.

These batteries have not been cycled but likely have been sitting in a warehouse for some time. Date codes on the BMS boards are mostly in the 2015-17 range. They have a variety of 2200mAH cells in them:
Sony - SE and SF
Samsung - ICR18650-22F
LG - LGDAS31865
Sanyo UR18650A

These cells seem to have a much wider range of capacities and there seem to be a few groups looking at the chart. There's still the 3500-3900mAH range like the 8-cell (LG) batteries had, but there's another cluster in the 2700-3300 range and then a few lower than that.

Initially I was disappointed in the lower capacity cells, but then realized that I need cells in this lower range to build some battery packs that match capacities of my extra modules built a while back.

Battery Hookup link for modem batteries (stock varies):
https://bit.ly/3ftt0LQ

More to come...

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Intro/Outro:
Louisiana Fairytale by Austin Rogers
https://web.archive.org/web/20170402222425/http://drfiddle.com/show_tune.php?id=94