iPhone 15 Pro Max battery health declining rapidly

own an iPhone 15 Pro Max, and I have noticed that the battery health has recently been declining at an unusually fast rate—approximately 1% every 5 charge cycles. This trend started around 298 charge cycles, and the device has now reached 313 cycles with the battery health at 86%.

I have been consistently following Apple’s recommended practices for maximizing battery lifespan, including using an 80% charge limit and taking care to avoid conditions that may accelerate battery degradation.

Given that Apple states that iPhone 15 batteries are designed to retain up to 80% of their original capacity at 1,000 complete charge cycles under ideal conditions, I am concerned about the recent rate of degradation. I understand that battery health is an estimate and does not necessarily decrease linearly, but the recent decline appears significantly faster than expected.

I would therefore like to understand whether this behavior can be considered normal for an iPhone 15 Pro Max or whether it could indicate an issue with the battery or its health reporting.