Please explain like I'm five: if continuously charging and drawing power at 100% hurts my laptop's battery, why doesn't the laptop bypass the battery circuitry, keeping it idle, and use the incoming juice directly?
If you blow on this balloon, it'll inflate. If you inflate it a lot and then let it deflate it has all of these stretch marks. Those stretch marks are now a permanent defect.
The same happens with your battery. If you charge it to 100% a lot and leave it there then it gets "stretch marks" and the permanent defects affect how long the battery lasts.
I am on the same MB Air since early 2019 and short of very occasional travel in the last 5 years it stays plugged in all the time. Just got back from a trip where I had more than 5 hours of heavy usage on battery and went nearly 6 hours before I was looking for an outlet.
I’m not unhappy with that…so I am always a bit skeptical of these laptop plugged in all the time are bad claims because it just doesn’t match my recent experience.
That maps out to roughly 65% charge state. So a little trickle charge on/off doesn't really help things much at all. You simply need to keep the battery in a lower charge state while plugged in for longer periods.
As bad as this is alone, the toxic combo that kills a plugged in laptop's battery in a year or two is regularly pushing it hard at full charge.
macOS actually does that somehow indeed. Not exactly, but it does prevent charge when it “guesses” the computer will stay plugged in for a long time based on previous usage.
Which isn't a solution, I just want a toggle so I know it works. I don't want to train some hidden logic so it correctly guesses what I want based on what someone on the other side of the planet assumed my usage pattern looks like.
…for you. For me, I am perfectly content with the algorithm deciding, and then me, deciding when I know I am going to be disconnected outside of my normal usage pattern…telling the machine to charge it to a 100%.
It does, if the battery is 100% no more charging current goes in, so charging stops.
But the key point is that the battery will drop to 99% very quickly and on it's own because no battery can keep the energy in perfectly. So it's recharged for the missing 1% over and over again which causes the damage.
Unless some smart charging logic prevents that, see other comments here.
It's not just this, it's literally bad to keep a lithium ion battery in a high voltage state, period. Simply taking a battery out and leaving it on the shelf in a high voltage state, otherwise unused, harms it.
Agree, not sure why though. Because the isolation degrades because of electrons breaking through it?
However, keeping "a lot" of energy in the battery is kind of the purpose, no one is using 50% max to increase battery life. But I guess most damage increases exponentially with energy stored, so charging it from 95% to 100% will damage it a lot more to than charging it from 90% to 95%.
The same happens with your battery. If you charge it to 100% a lot and leave it there then it gets "stretch marks" and the permanent defects affect how long the battery lasts.