Why does charging iPhone always seem to take longer while at 99%?

[iphonefreak450]

I have an iPhone 14 Pro with the battery health still on 100%.

But this is not just on my iPhone 14 Pro, as I had numerous previous iPhones before this.

I am just as to why the charging seems to take longer when at 99%? It seems to be holding at that percentage point for few minutes before it finally reaches 100%.

I’m using the Apple 20w USB-C to lightning charger.

But just out of curiosity, why does it charge the longest when at 99% before it reaches 100%?

Whenever I first plug it in to the charger, the charging goes fast, but why does it take the longest when at 99%?

Like I mentioned above, my battery health/capacity is still at 100%.

 

[antiprotest]

Because it knows you will unplug it at 100%.

 

[casperes1996]

Because of the way batteries work. Charging has to take longer the closer you are to maximal capacity for the longevity of the battery. 0-20% will also be faster than 60-80%.

Here's a good video explaining battery tech in broad strokes

 

[Helmsley]

Charging slows down as the battery gets closer to 100%.