FAST DECLINE IN BATTERY HEALTH

There is nothing wrong. That's exactly what you would expect out of normal usage.

Even rechargeable batteries get worn down and 1-2% health loss per month is perfectly normal. Referring to the "Your battery's maximum capacity" section of the support article: 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." Apple apparently only considers it unusual (and covered by warranty) if a battery drops below 80% maximum capacity in less than a year after you receive it. Ergo, some storage loss as you use it is anticipated and acceptable. A possible 20% drop over the first 12 months equates to 1-2% drop per month being within the range of what Apple finds acceptable. "The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge." In other words, if maximum capacity is below 80%, the battery is below normal performance and worth replacing. A notification will appear about this. You can still use a device with a lower health percentage than 80% but for optimal usage you may wish to consider having it changed when it reaches 80% battery health.

What this basically means:

- If battery health drops a few percentage per month that is normal.

- If battery health drops below 80% before the end of the first year, contact Apple about a warranty replacement. (Apple will test it to determine its actual eligibility.)

- If battery health drops below 80% (you will see a warning message) after the first year, consider getting the battery replaced but anticipate paying for it.

leogirl0819 wrote:

Comparing it to my sister's iphone 13 which she got earlier than me, she still has 100% battery health. So why is mine declining so fast?? We also follow the 30/80 method of charging. Not to mention my phone heats when charging even if it's not used.

Comparing an iPhone 13 used by someone else to your iPhone 15 is apples and oranges.

Regarding your "30/80 method of charging", that's unnecessary micromanagement. Turn on Optimized battery charging and put the phone on charge every night.

When to charge your iPhone or iPad - Apple Community

If you believe there is a hardware problem with your phone (I don't think there is), contact Apple and arrange for them to run diagnostics:

Genius Bar Reservation and Apple Support Options - Apple

Turn that around. Yours isn't wearing down quickly, hers is wearing down more slowly. Could be a dozen reasons. She doesn't use hers as much? She watches fewer things that cause increased battery wear?

Frankly I am doing better than either of you. I have an SE gen 1 that is probably 6 years old now and it still says it has 84% battery health. Of course I hardly ever use it for anything.

The 15 is a different device from a 13 so your comparison is a bit like trying to compare fuel consumption in two cars. You have a muscle car compared to her family van and my moped scooter.

Also remember that those numbers are not super precise.