I have a MacBook M1 that's only about two months old. I keep it connected to power all the time, and use it in clamshell mode so it's rarely powering the display.
The battery level dropped to about 85%, and it has been staying around there consistently. If I turn off "Optimized battery charging" it will return to 100%, but when I turn that off it drops again.
But I wonder why the charge is dropping in the first place. If it's always connected to power, it shouldn't use the battery at all, right?
The caption below the "Optimized barry charging" checkbox says
To reduce battery aging, your Mac learns from your daily charging routine so it can wait to finish charging past 80% until you need to use it on battery.
Does this mean that it's preferred to keep the battery around 80% when it's not using the battery? And since I never "need to use it on battery" it has learned this routine and keeps it there?