What does HackerNews think of thinkpad-ec?
Infrastructure for examining and patching Thinkpad embedded controller firmware
While swapping cells, just be careful to match voltage and severely limit current to avoid any danger/excitement. Sure you can find some forum posts on this. Also, the new and old cells must be brought very close in voltage as discrepancies are flagged disabling the battery. This also goes for between cells but allowable differences are larger. I think this battery has 3s3p configuration.
I've bought quality 18650 cells online 10 for about $100CAD for a x220 battery rebuild. More recently got 2x 2Ah 18v Ryobi packs which yeilded 10x cells total for $29CAD on clearance at Home Depot....
x230 FHD resource: https://forum.thinkpads.com/viewtopic.php?t=122640
https://www.reddit.com/r/thinkpad/comments/5p3mpm/how_to_fla...
+ https://github.com/hamishcoleman/thinkpad-ec for EC sourcecode
besides Allwinner A64 = tons of binary blobs, often containing gpled code and openly violating open source licenses