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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?

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  • This sounds normal and like everything is part of the optimized charging process. But I'd recommend unplugging it and seeing if it immediately charges back when you plug it back in.
    – Ezekiel
    Oct 7 at 1:34
  • Clamshell mode doesn't work when unplugged.
    – Barmar
    Oct 7 at 14:25
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If the power adaptor cannot cover the load then the difference is taken from the battery.

Once the load is reduced then the battery gets recharged.

Seen that on my macbook pro and it also depends on the size of the charger. So I can use a 65W charger and see that behavior, but when I connect my 85W charger it rarely happens.

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  • I’ve seen this on Intel chipsets but never Apple Silicon but I’m sure there’s always some charger that can’t keep up with some CPU and the same effect could happen here. I suspect it’s more likely there’s a hardware issue though for M1 to show this and most likely it’s the power source and not a M1 issue this soon, but however rare, some bad M1 portables have has to ship or break already too…
    – bmike
    Oct 7 at 8:27
  • @bmike will ask my son as he has an M1 and uses it quite hard…
    – Solar Mike
    Oct 7 at 8:29
  • I'm using the power adapter that came with the M1, the specs say it's 61W. So I guess that may be it.
    – Barmar
    Oct 7 at 14:23
  • I've updated the question. What I actually see is that it always hovers around 85% unless I turn off "Optimized battery charging". The caption says "wait to finish charging past 80% until you need to use it on battery". So is it staying there because I never use battery?
    – Barmar
    Oct 29 at 14:45

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