Glancing at some comments here mentioning the overnight charging feature working for them, am I in the minority by charging randomly whenever it needs it? My charger isn't even in the bedroom. Curious how my random on/off habits compare to overnighters in long term battery health.
I try to take it off around 80% so I was interested in this feature and confused when the update didn't include it. I don't like that it's in my "pros" column for upgrading when it could be available to everyone, would rather not reward them for that.
The world of lithium-ion battery chemistry is quite complicated, but in my experience, the top contributors to battery wear-out are, in decreasing order of severity:
- Charge cycles (including partial cycles, e.g. 100% -> 50% is half a charge cycle)
- Depth of discharge (deeper discharge cycles are worse)
- Extended periods in hot conditions (over 40 degrees Celsius)
- Extended periods of being held at 100% state of charge
In essence, your charging behavior dings the first two items: higher number of charge cycles, and deep discharge cycles. If your goal was battery longevity, keeping the phone plugged in as much of the time as possible would be the best strategy. Bonus points if your phone supports a "stop at 80%" mode, but still the winner even without this feature.
I think another huge killer of lithium batteries is charging them when below freezing. I bet most phones probably wouldn’t allow it though - or at least would limit it.
I left out things that a typical battery management system will prevent, like over/under charging, or operating outside safe temperature limits. But yes, charging a typical cell below 0 degrees Celsius will immediately and permanently damage it. Here's a ref with some details on why:
I try to take it off around 80% so I was interested in this feature and confused when the update didn't include it. I don't like that it's in my "pros" column for upgrading when it could be available to everyone, would rather not reward them for that.