iPhone 15 Pro Max Battery Capacity Reduction at 109 Cycle Count

Perfectly normal.

Batteries degrade over time with usage due to chemical aging.

You can expect about a 1% drop per month with average use on an iPhone. This is an approximation, that is why it may be plus or minus a few percent on a month to month basis.

Apple recommends replacing it when it reaches 80%.

iPhone Battery Replacement.

iPhone Battery Replacement - Apple Support

About Lithium Ion Batteries

iPhone battery and performance - Apple Support (IN)

Here are some tips on maximizing battery life.

Batteries - Maximizing Performance - Apple

You are very lucky.

It is normal for the battery to decline 1% for every 50 charge cycles. If your phone has completed 109 cycles, the battery health should be 98%.

Your battery is doing better than normal.

Your iPhone battery health is expected to drop about 1% for every 50 charge cycles, and the decline isn’t always linear. Meaning some months you may lose more than expected, other months none at all.

At 109 charge cycles, you should be at around 98% battery health. So you are ahead of your battery!

Keep in mind, all rechargeable lithium batteries chemically degrade over time. When your battery health reaches 80%, have the battery replaced.