Why my phone didn’t charge up to 100 just 80 percent

arah224 wrote:

Why my phone didn’t charge up to 100 just 80 percent only

Because you turn on the Optimized Battery Charging see this article to learn more about it ☞ About Optimized Battery Charging on your iPhone - Apple Support

This may be right answer .

Turn off Optimized battery Charging in Setting > Battery > Optimized Battery Charging.

If u want to know what is that Read it .

About Optimized Battery Charging on your iPhone - Apple Support

Alternatively charge it all night every night as advised and optimised charging (if you leave it on) will continue to 100% after a few days while it learns your habits.

Optimised charging after a week or so of correct charging.