My iPhone 13 shows measure decline of battery health when I update ios 17 in my iPhone 13

Hi there Malikmyser,

We’d like to start by clarifying how the maximum capacity of the battery in your iPhone relates to overall battery health. To start, it’s normal for the maximum capacity percentage to decrease over time. This is because all rechargeable batteries are consumable components. The rate at which it decreases is based on usage and other factors. Have a look at the ‘Your battery's maximum capacity’ section in this link: iPhone Battery and Performance - Apple Support

A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge.

If you see that the Maximum Capacity is below 80%, then it's time to replace the battery to restore full performance. This link will help you get started: iPhone Battery Repair & Replacement - Apple Support

Take care.