A bit odd. My new MacBook Air (Sonoma) was observed today to have battery level at 80% and NOT charging. This was after not having used it in 12 hours. It was plugged in, and everything at room temp. I diddled a little in the battery settings, and it started charging. Why doesn't the OS keep it at 100% when plugged in?? If I'm going to use it on battery power, I'd sure like it to be at 100% when I start doing so.