My iPhone 13 Pro Max battery health is declining faster than normal

To learn about maximizing (and the difference between) battery life and lifespan, read this support document --> Batteries - Maximizing Performance - Apple

Read this support article about iPhone battery and performance to learn about the battery health feature and what is considered normal performance --> iPhone Battery and Performance - Apple Support

To see the feature go to: Settings > Battery > Battery Health

"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." A degraded battery may display the notice: "Your battery’s health is significantly degraded. An Apple Authorized Service Provider can replace the battery to restore full performance and capacity." If it is not at or above 80% "normal", consider contacting Apple about a battery replacement. --> iPhone Battery Replacement - Apple Support

According to the above quoted information, you could be losing almost 2% per month the entire first year before Apple would deem this to merit a warranty replacement.

- Requires iOS 11.3 and for iPhone 6 and newer iPhones only, not iPad or Watch.

Also read this post by ASC contributor Lawrence Finch which has a very user-friendly explanation of battery features --> Bettery health maximum capacity - Apple Community

Don't obsess about battery health.

Unfortunately, there is no solution to battery health. Batteries don’t last forever and how your device uses it depends on many factors and variables.

🔋⇢🪫

If you don’t have AppleCare, then it is highly unlikely that the battery replacement will be free of charge when it eventually needs replacing.

Keep in mind:

All rechargeable batteries are consumable components that become less effective as they chemically age.

Recent software updates can accelerate that process by adding features that consume more power.

As lithium-ion batteries chemically age, the amount of charge they can hold diminishes, resulting in shorter amounts of time before a device needs to be recharged.

Apple won’t replace the battery until it reaches 80% capacity.

Battery Performance Tips:

• iPhone Battery and Performance.
• Check battery health and usage.
• Optimized Battery Charging.
• Maximizing Battery Life.
• Use Low Power Mode.
• About battery usage.
• Show battery percentage.

80% Battery Capacity?

Current Apple Prices:

• No charge for in-warranty or AppleCare+ plan.

Out of Warranty Prices:

• iPhone 13 Pro Max: $89 U.S. Dollars.

Click ▷ Check AppleCare Coverage.

Click ▶︎ iPhone Battery Replacement.

Good luck! 👋🏼😉