iPhone 15 Pro Max battery health drop after iOS 18 update

There is nothing wrong with your battery.

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.

There are dozens and dozens of posts like this that spring up after every iOS update for the past 20 years (i.e., it is coincidental) and it is normal to see a bit of heating. Some activities such as charging or a lot of computational activity (e.g., video), generate heat. Some warmth is to be anticipated.* "Keep your iPhone, the power adapter, and any wireless charger in a well-ventilated area when in use or charging."** Read this article about keeping your iPhone, iPad, or iPod touch within acceptable operating temperatures - If your iPhone or iPad gets too hot or too cold - Apple Support

Consumers want newer device models with larger batteries (= more energy to be lost as heat) and faster charging. This means more heat is released over a shorter period of time, resulting in higher temperatures. If you do not like this, use a lower wattage charger which charges more slowly.

In terms of usage, changes in software such as upgrades may introduce new features which may add to power drain and heat generation. Check Settings > Battery to see if there are apps running that use a lot of power. If there are, decide if you can turn off a service such as Settings > General > Background app refresh when an app is in the background, or Settings > Privacy > Location Services. Read this support article to learn about the battery health feature —> iPhone battery and performance - Apple Support

If you have just updated system software, read posts about indexing in this thread: iPhone 15 overheating - Apple Community

An iOS update may require subsequent reorganization of files and a short term increase in heat and battery drain until the task is done. Wait a few days and see if the issue persists.

If you think there is a problem with a device, have Apple inspect it. Go to this page to find your nearest Apple Authorized Service Provider (AASP) or Apple Authorized Distributor (AAD) --> Find Locations

How to make a Genius Bar appointment

1. Go to Genius Bar Reservation and Apple Support Options - Apple

2. Go to "Get hardware help".

3. Select your hardware and continue selecting options requiring replacing parts until you see "Bring in for Repair"

4. Sign in with your Apple ID

*"Your iPhone might get slightly warmer while it charges." - from: How to use your MagSafe Battery Pack - Apple Support

**Section about "Prolonged heat exposure" in this support article --> Important safety information for iPhone - Apple Support

Batteries, like people are individuals. No two people age exactly the same and batteries don’t age the same either. The exact usage, chemical makeup, storage conditions, exposure to heat and cold and about a dozen other factors mean that every battery ages differently. Battery aging is not a linear (straight line) and degrades at different rates as the chemicals in the battery age and other factors mentioned above. Apple expects your battery health to be at 80% after 24 months. If your battery health misses that expectation, contact Apple Support.

Please review the Apple Support articles on battery optimization. It contains the best  current practices for battery charging.

iPhone Battery and Performance - Apple Support

Batteries - Maximizing Performance - Apple

About the battery and performance of iPhone 11 and later - Apple Support

If an "Overheating" message is not appearing on your phone, your phone is not overheating.

If you feel that the iPhone is not operating correctly, please make an appointment at the Apple Store or take the phone to an authorized Apple service shop so the phone can be checked and tested.

You can find a list of authorized service shops in your area using this link: Find Locations

If it is not possible for you to take the phone in for testing, Apple Support might be able to run a remote diagnostic on your phone. You can contact Apple Support here: Official Apple Support

I have a feeling that the technicians will confirm to you that there is nothing wrong with your battery. Please post back on your results after the phone is checked.

Please post a screenshot of your phone with the "Overheating" message.

It's not always the iOS update's fault!  Many things can cause phone problems.  If you tell people you think it's an iOS update, it might make it harder to fix or find a solution for the real issue.

Remember, the right question often leads to the solution!

iOS updates aim to enhance user experience, boost security, and fix bugs rather than disrupt core features. The majority of the issues after updates might stem from underlying, unmentioned factors. Updates won't typically alter personal data but may refine settings or features. Backup before major updates for safety. Review Apple's update details and backup advice for a smooth process.

Kindly consider checking your settings and addressing any device issues before attributing the issue to external factors. This could be a pure coincidence that the iOS update affected the iPhone functions.

Before initiating a standard iOS update, it's advisable to create a backup. Have you completed this step? If yes, proceed with the restoration from the backup.

See what each update does: About iOS 18 Updates, About iOS 17 Updates, About iOS 16 Updates, About iOS 15 Updates, About iOS 14 Updates, About iOS 13 Updates, About iOS 12 Updates, and so on...