"About 80% Limit with iPhone 15 models
With iPhone 15 models, you can choose between Optimized Battery Charging, 80% Limit, and None.
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."
[Edit: This is new to me too. I did see one day where it charged to 94%, but it's been 80% ever since. Yesterday did a 8 hour drive with Carplay, and it stayed at 80% too. Nice feature for my usage pattern.]