As someone who has to use a laptop for work, I keep my laptop plugged in 8 hours or more a day, 7 days a week. The laptop's battery during these days would discharge and charge, slowly degrading the battery because only the last ~ 20% would be charged and discharged …
There’s other things that happen to a battery as it ages. Voltage sag with heavy current draw is one. An app that measures capacity may not take this into account. It may look fine and be at full voltage with light usage, but then launch a CPU-heavy app and it drops down a few tenths of a volt and isn’t able to hold the voltage.
If it’s discharged enough, sometimes this will drop the voltage enough to cause the phone to shut off even if it has a decent charge, say 20-30%.
You’ll notice this in reverse too. The battery will seem to start charging faster than usual, but then the rate drops off dramatically as it gets close to full.
There’s other things that happen to a battery as it ages. Voltage sag with heavy current draw is one. An app that measures capacity may not take this into account. It may look fine and be at full voltage with light usage, but then launch a CPU-heavy app and it drops down a few tenths of a volt and isn’t able to hold the voltage.
If it’s discharged enough, sometimes this will drop the voltage enough to cause the phone to shut off even if it has a decent charge, say 20-30%.
You’ll notice this in reverse too. The battery will seem to start charging faster than usual, but then the rate drops off dramatically as it gets close to full.