FWIW, my 13 mini (approaching 3 years old) shows a maximum capacity of 80%. This is charging it every night (using the Optimized Charging feature), rarely charging it during the day, and running the battery down to about 30-50% most days.
Since I can’t directly read the cycle count from an iPhone 13 (why, Apple, why?) I used this shortcut to pull the data from the phone’s analytics logs. It reports:
- Original maximum capacity: 2488 mAh
- Nominal (current) capacity: 1908 mAh
- 578 charge cycles
This yields a maximum capacity of 77% (1908 / 2488)
The official maximum capacity for an iPhone 13 mini’s battery (according to iFixit) is 2406 mAh. Which would yield a capacity of 79% (1908 / 2406).
The power management chip built-in to most rechargeable Lithium batteries can report its capacity, in units of mAh (milliamp-hours). The percentage capacity reported should be this capacity divided by the manufacturer’s spec for the capacity of a new battery.