All the UPSs that I have operate "switched" while AC power is present, they pass it directly to their outlets. When AC power drops they switch very quickly
to an internal power-inverter so all the device under load sees is a "glitch" on the line which for most things doesn't cause a problem.

When power is on, the UPS changes it's battery - how well it does this depends on the quality of UPS. Some cheap ones just trickle change
constantly (and may need batteries replaced more frequently) - better ones monitor/test the battery charge level and will fast charge to a good
amount, then trickle to "full" then just maintain)

You can hear the UPS inverter running when power is off. The internal USP battery isn't very big and can usually only run the inverter for a few mins.
(At one time I built my own UPS for my server which had a lawn-tractor battery and could go 1/2 hours - but it also monitored the server 5v power
and could "press" it's front panel button. Like all UPSs it switched on power failure, but unlike most, if the power had been off for 10 mins,
it would tell the server to shut down by pressing it's front panel button, then wait for it to shut down (till 5vrail drops) then go offline waiting for power
to restore - when power did restore, it waited to confirm it was stable for 5mins before it would restart the server.
- I often traveled, and used my server remotely - many times power failed while I was away (rural location) and I never had problems with the
server or had it fail to come back online.

Laptops are different - they don't run on AC power - the power adapter provides DC (usually 19v) and the switch to the battery
is much simpler - how it charges it's battery varies (like described above for UPS) but most laptops have good/smarted charging.

Old laptops which ran on NiCD or NMiH batteries could suffer battery degradation if not discharged from time to time (and battery could be damaged it discharged to far).
Newer laptops with lithium batteries don't have this problem (although I do like the exercise them occasionally just so I know the battery isn't failing)

Following 40-80 rule is supposedly the best for lithium batteries. My laptop has the function to keep it at 60% when plugged in. Still, over the course of 11 years, it seems to have lost good amount of capacity and the meter isn't accurate, it shows depleting at slower rate, then suddenly jumps to single digits.

UCyborg wrote on Yesterday, 20:59:

Following 40-80 rule is supposedly the best for lithium batteries. ...

Good point, I forgot to mention that Laptops with Lithium batteries won't take the "just trickle charge" route - Lithium can have problems (even explode) if overcharged, so anything with Lithium should have a "smart" charger.

These however can vary in how well they look after your batteries - no manufacturer wants to have the legal hassle of making products that explode on people, but many don't think it's a bad thing at all if you have to buy their proprietary battery from then more frequently.

All my laptops that are used mainly with power have batteries removed. Just to be safe. Thank god, they still work. But some phones and tablets do not.

^^ That might be a good approach. But, the battery should still be taken for a spin every once in a while, if I'm not mistaken. Aren't lithium batteries slowly losing charge when unused?

Cyberdyne wrote on Yesterday, 21:52:

All my laptops that are used mainly with power have batteries removed. Just to be safe. Thank god, they still work. But some phones and tablets do not.

Yes, I do the same - but I have run into laptops over the years that needed their battery even when running from power adapter.
Fortunately I don't have those anymore (IIRC they were old Eurocom laptops with NiCD batteries and relied on the
battery as part of regulation - or something like that)

UCyborg wrote on Yesterday, 20:59:

Following 40-80 rule is supposedly the best for lithium batteries.

+1 this ^

If your laptop has a feature to set to what percentage to charge the battery, try setting it below 70% if possible... unless you frequently use your laptop on batteries and for extended periods of time - then you might want to go more to simply get more run time out of the battery.

In general, if you want your lithium batteries to last:
- try to keep them charged anywhere between 20-70% (50% would be ideal, but you'll get less run time on the battery, obviously)
- occasionally charge them to 100% to "exercise" the battery, following by using them down to that 20-70% range mentioned
- keep them cool (but not too cold, and especially best to avoid going below freezing or much above 30C). 10-20C is optimal.
- limit the number of charge-discharge cycles
- avoid "fast charging" and also fast discharging (e.g. gaming on the laptop or doing anything CPU/GPU intensive) while running on batteries. Fast charging and discharging raises the internal temperature of the battery, which as mentioned above, is part of what causes degradation.

So in regards to your question(s)... first see how often you want/need to use the laptop on battery.
- If not often or at all, it might be best to charge the battery to something like 50% and leave it at that. If the laptop doesn't have the option to do that, charge to 50%, then remove the battery and keep it stored nearby. Obviously this 2nd suggestion is not so great in case your AC power gets cut (then your laptop would shut off instantly too.) Where I live (in the city), power almost never gets cut, and since I almost never use my laptop on batteries, I have my battery removed. It is an old laptop, though, with easily removable battery. On a lot of new stuff, I suppose you can't really do that, as often the batteries are not removable (not without taking the laptop apart.)
- If you do plan to use the laptop on batteries somewhat more often or have a lot of power cuts where you live, then perhaps try to keep the battery charged a little higher: 60-70%, just so you have some reserve in case the power does go out for a longer period of time and you need to use your laptop. And it would probably be a good idea to keep the battery in the laptop then.

UCyborg wrote on Yesterday, 22:07:

Aren't lithium batteries slowly losing charge when unused?

Yes.
Actually, this is true for ALL battery chemistries. Obviously some battery chemistries loose charge much faster than others (e.g. CR2032 can usually last for at least a few decades without self-discharging.)
In regards to rechargeable lithium batteries - they usually have a pretty high capacity to self-discharge ratio, so that's why they can often sit on the shelf for a long time (sometimes even years) and still retain good charge. FWIW, I left my cordless toolset in storage in the US two years ago. It comes with two 20V 7 AH batteries. One was nearly fully used, while the other was probably somewhere around 50%. When I came back to them this summer, they were surprisingly, almost still retaining the same charge that I left them with.

DaveDDS wrote on Yesterday, 20:58:

All the UPSs that I have operate "switched" while AC power is present, they pass it directly to their outlets. When AC power dro […]
Show full quote

All the UPSs that I have operate "switched" while AC power is present, they pass it directly to their outlets. When AC power drops they switch very quickly
to an internal power-inverter so all the device under load sees is a "glitch" on the line which for most things doesn't cause a problem.

When power is on, the UPS changes it's battery - how well it does this depends on the quality of UPS. Some cheap ones just trickle change
constantly (and may need batteries replaced more frequently) - better ones monitor/test the battery charge level and will fast charge to a good
amount, then trickle to "full" then just maintain)

You can hear the UPS inverter running when power is off. The internal USP battery isn't very big and can usually only run the inverter for a few mins.

Laptops are different - they don't run on AC power - the power adapter provides DC (usually 19v) and the switch to the battery
is much simpler - how it charges it's battery varies (like described above for UPS) but most laptops have good/smarted charging.

Old laptops which ran on NiCD or NMiH batteries could suffer battery degradation if not discharged from time to time (and battery could be damaged it discharged to far).
Newer laptops with lithium batteries don't have this problem (although I do like the exercise them occasionally just so I know the battery isn't failing)

Yes, the systems are same for my desktop UPS. About glitches, I may see just a voltage fluctuation but with a better monitor, I don't experience that either. Not too much an issue.

About my laptop's charging, I am not sure of the smart charging that it uses, it is relatively new with a R7 AI cpu, so I assume some form of control there.

UCyborg wrote on Yesterday, 20:59:

Following 40-80 rule is supposedly the best for lithium batteries. My laptop has the function to keep it at 60% when plugged in. Still, over the course of 11 years, it seems to have lost good amount of capacity and the meter isn't accurate, it shows depleting at slower rate, then suddenly jumps to single digits.

Is the 60% setting in some OEM app or it can be controlled by some universal Windows program?

Cyberdyne wrote on Yesterday, 21:52:

All my laptops that are used mainly with power have batteries removed. Just to be safe. Thank god, they still work. But some phones and tablets do not.

Sadly, my laptop's battery is internal and there's no other way to get access to the brick.

momaka wrote on Today, 05:42:

- If not often or at all, it might be best to charge the battery to something like 50% and leave it at that.

Do you mean stop the charge at 50%? Do you have a setting that does that?