This might seem like a strange post but it’s caught me out recently. iOS introduced a feature to help reduce battery ageing where it charges to 80% first then drip feeds it after that based on your usage.
With my iPhone 13 Mini I realised I was having less at the end of the day. I checked my charging and it wasn’t getting to 100% on the overnight charge.
Turning off this setting now means I’m back to full charge in the morning and getting more from my iPhone in the day.
You can turn off this setting by going to settings, battery, battery health then turn off optimised battery charging.