[theamk]

All of the controllers do that! But then battery starts to self-discharge, eventually a controller detects "huh, the battery is no longer charged" and start charging again.

Over years, this can accumulate enough charging cycles so battery gets worn down.. And old batteries have even higher self-discharge, so the cycle accelerates. If you are lucky, the battery lasts long enough. If you are unlucky, you end up with "spicy pillow". If you are super unlucky, and charger's temperature sensor fails (or was never installed), or battery gets punctured - you got a fire.

[butvacuum]

Not all of them apparently. I'll have to dig for a schematic(they exist, but places want money), but it seems my Dell laptop from 2019 uses the embedded controller as the BMS.

As, somehow it managed to turn all four cells in the pack into pillows. Which indicates a shockingly flawed balancing system