Why is my iPhone 15's battery health dropping?

According to Apple's official article about Battery Health and performance:

It's normal for your iPhone 15 battery health to decrease slightly over the first year. The battery is designed to retain up to 80% of its original capacity at 1,000 complete charge cycles under ideal conditions. Factors like the number of charge cycles, device usage, and exposure to extreme temperatures can all impact battery lifespan.

Tips to maximize battery performance:

1. Keep your iPhone in moderate temperatures: Avoid leaving it in hot or cold environments.
2. Enable "Optimized Battery Charging": This helps reduce battery aging.
3. Avoid full discharges: Try to keep your battery level between 20% and 80% when possible.

A slight drop in battery health is normal and expected, but if it decreases significantly (below 80%) within the first year, your device may qualify for a battery replacement under warranty. Regular use and proper care will help maintain the battery's performance over time.

Batteries are consumables; they lose a little capacity every time they are discharged, then recharged. On average this works out to about a 1% loss for every 25 “full charge cycles”. As one example, if you charge the phone overnight, every night (and that is what you should do; it is a best practice), it starts the day at 100%. If it drops to 20% by the end of the day before you charge it again overnight that counts as 0.8 full charge cycles (20% to 100%), or about 24 full charge cycles per month of use. For this example your battery capacity will lose about 1% per month. Of course, if the end-of-day level is higher than 20% the capacity loss will be a little less, and if it is lower than 20%, or you charge it during the day, the capacity loss will be higher.

If you have an iPhone 15 or higher you have an even more useful measure: cycle count. And the 1% for every 25 cycles still counts. Thus, your 76 cycles corresponds to a drop to 97%, and you are ahead of the game.

Once the capacity drops below 80%, or if there is a message in Battery Health that the battery is not meeting peak performance expectations, it’s time to change the battery→iPhone Battery Replacement - Official Apple Support

AppleAnswerDude wrote:

According to Apple's official article about Battery Health and performance:

It's normal for your iPhone 15 battery health to decrease slightly over the first year. The battery is designed to retain up to 80% of its original capacity at 1,000 complete charge cycles under ideal conditions. Factors like the number of charge cycles, device usage, and exposure to extreme temperatures can all impact battery lifespan.

Tips to maximize battery performance:

Keep your iPhone in moderate temperatures:1. Avoid leaving it in hot or cold environments.

Enable "Optimized Battery Charging":1. This helps reduce battery aging.

Avoid full discharges:1. Try to keep your battery level between 20% and 80% when possible.

A slight drop in battery health is normal and expected, but if it decreases significantly (below 80%) within the first year, your device may qualify for a battery replacement under warranty. Regular use and proper care will help maintain the battery's performance over time.

Actually, no; it will remain above 80% for 500 cycles.