Battery charging 80% limit not always working

Your iPhone has to charge to 100% occasionally or the algorithm to determine remaining charge/capacity is inaccurate. You iPhone may even charge to 100% several cycles in a row. What you’re experiencing is normal.

Optimised Battery Charging is designed to reduce the wear on your battery and improve its lifespan by reducing the time your iPhone spends fully charged. It is ...

About Charge Limit and Optimised Battery Charging on ...

This is normal and expected behavior. Apple notes this in several support articles.

>>If you have Charge Limit set to less than 100 percent, your iPhone will occasionally charge to 100 percent to maintain accurate battery state-of-charge estimates.<<

About Charge Limit and Optimized Battery Charging on iPhone - Apple Support

The iPhone has to do this so it can calibrate to 100% battery capacity. It’s normal. 

Same here, same phone and same problem, I have had it for 3 weeks and it has never charged beyond 80%, but yesterday it did :/ on 18.3 too

Please review my post and support article I linked to.