iPhone charging to 100% even when optimized to charge up to 80%

Check the Battery settings again carefully and note that although the charging might be set to 80%, that the phone will still occasionally charge to 100% in order for the battery to calibrate correctly.

In my case, "occasionally" is sometimes about once a week. Your experience will likely be different. In any case, this is nothing to be concerned about since this is normal.

Here is what Apple says in their support document: About Optimized Battery Charging on your iPhone - Apple Support

When you choose 80% Limit, your iPhone will charge up to about 80 percent and then stop charging. If the battery charge level gets down to 75 percent, charging will resume until your battery charge level reaches about 80 percent again.

With 80% Limit enabled, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates.

If Optimised Battery Charging won’t activate --> About Optimised Battery Charging on your iPhone - Apple Support (IN)

Optimised charging is designed to only engage in locations where you spend the most time, such as your home and place of work. The feature won’t engage when your usage habits are more variable, such as when you travel. Because of this, some location settings must be enabled for Optimised Battery Charging to activate.* None of the location information used for this feature is sent to Apple.

Follow these steps:

• Go to Settings > Privacy & Security > Location Services and turn on Location Services.
• Go to Settings > Privacy & Security > Location Services > System Services and turn on System Customisation.
• Go to Settings > Privacy & Security > Location Services > System Services > Significant Locations and turn on Significant Locations.

Learn more

Find out what to do if your device stops charging unexpectedly.

Not a big deal, but the information that you were not aware of was right there in the first response that you received from SravanKrA.

You must have missed that information. I simply repeated that info in my response.

No worries. Glad that we got things figured out.