Any idea what caused sudden battery use in M1 MBP 14"?

I opened my M1 Max MacBook Pro 14" to check the battery status and discovered that the MBP re-booted and displayed the battery percentage at 10%. The MBP had been left in the sleep mode, lid closed, with the battery in the 47 to 50% range for the previous 24 hours. It appears that the battery % steadily declined over the previous 8 hours from 50% to 47%, then dropped suddenly to 10% from 8:00 pm to 9:00 pm (see battery level graph below).

The only apps running were Messages and 1Password. There was no web browser running.

After the MacBook re-booted I launched Activity Monitor to see if any clues could be seen. See screenshots from Activity Monitor below. Battery Health is reported “Normal” with Maximum capacity 100%. Battery has only 57 charging cycles reported.

Can anyone explain this?

It’s hard to tell from this, as nothing particularly stands out. “12 hr Power” is a relative measure dependent on several factors and the Photos library deamon being at 12 is not much overall so it’s not that.

It would have been good had you had the chance to run the Activity Monitor before rebooting the Mac as some apps may have been preventing sleep at the time (see last column) and sorted themselves out following reboot.

If it does not happen again, I would attribute this to some runaway process or a bad-behaving app at the moment and would not worry much.

Yes, of course, and thank you. Unfortunately this was not possible because the Mac had already shut itself down, then re-booted automatically when opening the lid. Apparently when the Mac is in sleep mode and the battery reaches a certain level (10% in this case) the Mac powers off automatically. I had no choice other than allowing the Mac to re-boot from a shut-down state.

It would be nice if these MacBooks had an always-visible battery charge level indicator, even with the lid closed. If that were available, you could see when the charge level reaches 20 or 30%, prompting you to open the lid and check the Activity Monitor before the Mac powers itself down.

You can see from the battery level graph above that the time interval between 47% charge and 10% charge was very short. Absent an always-visible charge level indicator, it would be almost impossible to catch this type of rapid battery depletion before auto-shutdown.

Any chance there were a large number of photos being analyzed?

That is possible. Sometime yesterday (same day this battery drain issue occurred) I checked the Duplicates feature for the first time in the Photos app. 5,056 photos and 33 videos were reported as duplicates. For reference, there are 20,647 photos and 326 videos in my Photos Library.

Do you suppose that a process in the Photos app was triggered, draining the battery while the MacBook was in a sleep state? Would there be any type of log available that would report this?

No idea on the logs, but if it’s running checking on that many photos and videos I could absolutely see the CPU being pegged by that activity.

I would think that would be especially true with videos. Video decoding is CPU intensive. Even if the CPU is optimized for the codec, it still takes a fair bit of juice.

Absent any other information, speaking personally, I would assume that’s the problem.

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I agree, thank you. Time will tell. I will monitor daily for a while. Since battery health is normal and battery capacity is reported as 100%, there is nothing else to do.