FC5 laptop powers down despite full battery 2019

That's not "memory effect", that's damaged cells. The memory effect people used to refer to had to do specifically with NiCd technology, which nobody uses in laptops anymore. Partially discharging the cells repeatedly to the same level would result in loss of capacity.

Most laptop batteries are Lithium (Li) now, and those are very finicky about charging procedures. Their chemistry is completly different from the old NiCd and NiMH cells and they therefore behave differently.

The "reconditioning" process you describe applies to NiCd cells but I don't think it is a good plan for Lithium. Most Li packs include undervoltage protection anyway, to prevent damange to the cells from excessive discharge.

Agreed, overcharging is bad. But it is less bad for some kinds of chemistry than for others. For NiCd and NiMH batteries the typical scenario that leads to overcharge is trickle charging. That is convenient but slowly kills the battery. I've never seen one catch fire, but they can sometimes vent.

Overcharging Li is a different thing. It is a serious safety concern. Trickle charging Li is a very bad idea. Just Don't Do It. Since the chargers are designed to prevent it for safety reasons, I don't think Lithium batteries get overcharged very often or there would be a lot more fires than there are.

Most of the battery fires that get reported seem to be caused by the battery being shorted out by damage of some kind. The max discharge current of a Li cell can be pretty high.

FWIW, I believe many (most?) Lithium cells (or the chargers) do include temperature protection. Which isn't to say it always works.

-- - Bob Hauck - A proud member of the unhinged moonbat horde.