Stop laptop battery from charging beyond certain point

[MK27]

Are you really sure you want to argue electronics with an engineering technologist who's twice your age?

I don't care if you're the Pope. Your CV doesn't matter to me at all if half the time you speak logic and reason go flying out the window. I've been a witness to too much "expert incompetence" to believe anything else.

All one has to do is design the charging circuit to switch at about 95% of that voltage and you have achieved the desired combination of longest per-charge use time without degrading the overall lifetime of the battery.

Again, this "95%" is a number you have just pulled out of the air in relation to "desired combination", which is exactly the point of the discussion: the longer the per-use charge, the shorter the lifetime of the battery.

BUT, if you would stay with the original question, the concern was not about running the laptop on batteries every day it was about overcharging the batters because he *DOES NOT* run it on batteries all the time...

Your three card monty style rhetoric obviously doesn't fool many people, why do you bother?

Neither I nor anyone else have said anything about "running on batteries all the time" (except equating 1000 charges with 3 years of daily use), nor was overcharging the original question:

Anyone know of a Linux (and Windows) program to stop laptop charging past a certain point?

For example, right now I am using my laptop as a desktop replacement, and I want the battery installed for backup. However, by default the battery will be charged to and maintained at 100%.

100% is bad for long term storage. I want it to be maintained at 40% instead.

I don't see anything about overcharging in there -- clearly the OP recognizes that the battery is "by default...charged to and maintained at 100%". There is no concern about it being inappropriately overcharged by the charger. You are tilting windmills, as often seems to be the case. Evidently all your decades of knowing everything has still not left you with much skill at reading comprehension or thinking clearly.

What I do see, quite plainly, is the statement that someone believes storing a battery at 100% (normal, recommended, whatever) capacity is worse for the battery than storing it at 40%, which according to all reports I found is true, and is the reason I started leaving my battery out when not in use. No one in the world but you has even tried to refute this -- or maybe you have a source for such wisdom beyond your own pomposity?