Asklemmy

Yes, the battery doesn't charge to "dangerous - could explode" levels. But they very much do still charge to levels that are damaging to long term health/capacity of the battery.

Yes, they tune the batteries so that 100% isn't the absolute cap. But even with that accounted for, many batteries will be above values that would be considered good for the long term health of a lithium cell. 80 percent on most phones is still very much at levels that are considered damaging to lithium batteries.

To put it another way, the higher you charge a lithium battery, the more stress you put on it. The more stress you put on it, the fewer charge cycles those components will hold. It's not like there's a "magic number" at 80 percent, it's just that the higher you go the worse it is. Yes, some manufacturers have tweaked charge curves to be more reasonable. But they've also increased limits. Many batteries now charge substantially higher than most people would consider sustainable.

And after such changes, 80% lands pretty close to the general recommendations for improved battery longevity. Every percent will help, but it's not a hard and fast rule.

Calibrations have gotten a little better in some ways, but all you have to do is look at basic recommendations from battery experts and look at your phones battery voltage to see that almost every manufacturer is pushing well past the typical recommendations at 90 or even 85 percent.