Clamshell Mode - Battery Drop when Disconnected

[chefwong]

I have my MBP set to charge to 90% . It's generally in clamshell mode
If I disconnect it for travel, without usage, I see it has dropped to 80% .

I'm clear all batteries need to be -cycled, excercised- to be healthy.
Would we say the OSX is draining the battery when it's disconnected in order to cycle-calibrate the battery as needed

-Alan

 

[benholt]

Couple of things stacked here rather than a calibration cycle. With the 90% cap set, the pack self-discharges from 100 down toward 90 rather than being trickle-charged back up, so if it's been plugged in for a while the real state of charge is already drifting a few points below the 90 you see displayed. Unplug and the true reading unmasks.

Then even a sealed clamshell sleep has some background activity — iCloud sync, Bluetooth peripheral polling, Power Nap tasks. 24 hours of that easily shaves another 3–5% on top of whatever drift was already there.

Apple Silicon doesn't really do a hardware calibration cycle the way old Intel MBPs did, the fuel gauge is software-modeled continuously. System Settings > Battery > Battery Health > (i) shows cycle count and max capacity if you want to sanity-check the pack itself.