macOS recently introduced the ability to limit your battery to only charge up to 80%, a feature that I personally appreciate as I’m mostly using my MacBook plugged into a dock and it’s arguably a great way to limit the ageing of the unit.
There’s just one huge problem. Well, two actually. Firstly it doesn’t allow me to set a minimum charge (“start charging when battery is at X%”), so when it falls to 79% it just tops it back up to 80, not a big deal but slightly annoying. The much bigger issue is that the charge limit apparently isn’t being saved to the battery firmware itself so when the MacBook is turned off and plugged into my dock it just keeps on charging to 100%…
Similar issue with my Pixel 9 Pro, it normally sticks to the charge limit quite well, but multiple times a month I’d say it just randomly charges to 100% regardless. Apparently that’s to calibrate the battery or something? As far as I know you have to do a complete cycle to calibrate a battery which 80% to 100% isn’t, also I don’t think a Li-ion battery needs to be calibrated this often, does it?
To contrast, KDE Plasma retains the limit at all times, lets you set a minimum amount and actually tells the battery to always stop charging at that amount.
Am I just not getting something about this?
That’s excessive. There’s just not that much drift in accuracy in the space of a week. Monthly would be enough.
I don’t believe that because this isn’t about capacity calibration, but more so that the battery voltage is almost constant between about 20% and 90%, though varies by battery type, and no matter what, the controller can’t exactly know how much the battery is actually charging and discharging so it has to guess the current state. I’ve seen this happen on a Dell XPS laptop I have from work, I manually set it to limit charging to 80% since the built in “Primarily AC Use” mode cycles it around 95%, and it doesn’t do the occasional recharge to 100% by itself, so about once a month it would jump from whatever percentage it was at to 7%, even from 80%.