Does your screen dim as if you unplugged it before it happens? Happens to mine, I’m thinking the charging brick is the culprit for that. You can check the battery history and see if it jumps on/off charging before going full.
Otherwise it’s probably working as intended, it will charge to 100% right before it thinks you’ll unplug.
Screen doesn’t dim. It’s connected to a Studio Display, no disconnections in the battery history.
It actually did end up going down to 80% eventually, a couple of days after I posted this, and staying there, like on previous OS versions.
So it could be that the more rapid-paced discharge/hold/charge that I described is a new phase of battery management introduced in Sonoma that kicks in before it decides to limit the charging to 80% more permanently. Or it could just be buggy behaviour.
I really wish they would just give us a toggle in settings to limit charging to 80%, like they did on the new iPads. No matter how smart the smart battery management gets, there’s no way to make it understand the “I’m at home but will occasionally disconnect the laptop from the display for a few hours” scenario. When I do that, I would rather it keep the 80% limit on. But once you disconnect, for whatever reason, it will start charging to 100% unless you leave it plugged in for several weeks again (in my case, anyway).
Yes, I’ve tried AlDente but there are too many limitations. We need this toggle in the OS.
Update a day later: it started doing the discharge/hold/charge thing again, without my changing anything.