Lithium ion batteries do not like being charged at full capacity for extended periods. The aim of this new macOS behaviour is to reduce the amount of time MacBook batteries sit at 100%. And that’s why this feature is right down my alley. As a laptop-as-desktop user, my MacBook Pro is plugged in for most of the day. I am aware of the optimal battery conditioning procedures but — like everyone else — I can’t be bothered to micromanage it to that degree, so naturally my laptop sits fully charged for hours at a time, day in and day out. I just have to accept that I am not going to eek out the maximum number of recharge cycles from the machine. As of macOS 10.15.5, I won’t have to accept this penalty. With the setting enabled, my laptop will learn that it needs to charge to 80% and no more, naturally extending the lifetime of the battery without me having to manually regulate it.
I do think the feature could be implemented a bit more effectively though. In cases when you do want to charge to full, like if you know you are going to be away from a power adapter for a while, Apple’s answer appears to be to dive into System Preferences and disable the checkbox. This is functional but a bit inelegant. When I’m no longer mobile, I’ll have to remember to re-enable automatic battery health management. I’d prefer it if the Battery menu in the menubar had a one-click ‘charge to full’ button. This would allow the MacBook to reach 100% impromptu, but default back to the 80% behaviour for subsequent recharges.
Secondly, I find it curious that Apple chose to brand this setting as battery health management. This terminology closely overlaps with the iOS suite of Battery Health features, which encompasses things like the infamous performance throttling policies. The Mac behaviour has nothing to do with unexpected shutdowns or performance, though, it’s solely motivated by the desire to maximise the MacBook’s lifespan. As of iOS 13, iPhone and iPads do this too with a feature called “Optimized Battery Charging”. It would be more sensible if Apple used that exact term on the Mac too.