Battery drain on iPhone 16 Pro Max after iOS 26.2 update

According to Apple:

If you notice that your battery life has decreased after updating your device, wait a few days and then check again.

Even though you can use your device immediately after an update, certain tasks related to the update continue in the background and might affect battery life and thermal performance. While they're ongoing, you might see the Insight Ongoing iOS Update in Settings ➢ Battery.

• Learn why ⇢ the battery in your iPhone drains too quickly for details.
• Learn how to update your iPhone to the latest version of iOS.
• Learn what to do If your iPhone won’t update for step-by-step instructions.

Need more help?

• Call 1-800-APLCARE.
• Contact Support.
• iPhone Support.
• iPhone User Guide.

Good luck! 👋🏼😉

The measure of battery health deterioration/drainage is subjective and can vary depending on individual usage patterns. There is no universal standard to determine whether the battery health deterioration/drainage is normal or abnormal because it heavily relies on how the battery is used and maintained.

Protect & Prolong the Life of your iPhone's Battery:

1. About the battery usage on your iPhone, iPad, and iPod touch ...
2. Batteries - Maximising Performance - Apple (IN)
3. iPhone Battery and Performance
4. About Charge Limit and Optimised Battery Charging on iPhone - Apple Support (IN)

• Find out what to do if Optimised Battery Charging doesn’t activate.
• Find out what to do if your device stops charging unexpectedly.
• Find out what to do if you think your battery is draining too quickly.
• Find out how to charge and maintain your iPhone battery.

Try to monitor Battery usage by iPhone Activity as shown below

What is shown under battery usage? Checking that would give you an indication of the usage behavior.

1. Background Activity
2. Notifications
3. Connected to Charger
4. Or any Other

Try some of these options too.

To prolong the life of your iPhone battery, you can follow these tips and best practices:

To prolong the life of your iPhone battery, you can follow these tips and best practices:

1. Optimize Battery Charging: Enable the "Optimized Battery Charging" feature on your iPhone. It helps reduce the wear on the battery by slowing down the battery aging process. You can find this option in Settings > Battery > Battery Health. About Optimized Battery Charging on your iPhone - Apple Support (IN)
2. Avoid Extreme Temperatures: Extreme temperatures, both hot and cold, can negatively impact your battery life. Avoid exposing your iPhone to excessive heat or cold, such as leaving it in direct sunlight or in a freezing car.If your iPhone or iPad gets too hot or too cold – Apple Support (UK)
3. Use Original Chargers and Cables: Always use Apple's original chargers and cables or certified third-party accessories. Low-quality chargers or cables can damage the battery and reduce its lifespan. Identify counterfeit or uncertified Lightning connector accessories - Apple Support (IN)
4. Avoid Draining the Battery to Zero: Charge it whenever the charge becomes lower than 20%. The rest is up to you when to charge. how long to charge, how often to charge, which adapter to use starting from 5W to 140W USB-C Power Adapter etc.
5. Optimize Display Settings: Adjust your display settings to optimize battery life. Lower the screen brightness, enable auto-brightness, and use shorter screen timeout durations. Adjust the display and text size on iPhone - Apple Support (IN)
6. Minimize Background App Refresh: Limit the number of apps allowed to refresh in the background. Go to Settings > General > Background App Refresh and disable it for apps that don't require real-time updates. Switch apps on your iPhone, iPad, or iPod touch - Apple Support (IN)
7. Disable Push Email: Push email notifications can drain your battery quickly. Instead, set your email accounts to fetch data manually or at longer intervals. You can change this setting in Settings > Mail > Accounts > Fetch New Data.

there is a simple faulty battery test overnight, off charge, powered off

Check your iPhone battery for Self-Discha… - Apple Community

Read it carefully

(PS I think you meant USBC cable)

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!

Was/Is your device Jailbroken? If that's the situation, please be informed that attributing the issues to iOS updates may not be accurate.

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: OS — iOS 26, 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...

It surely is not iOS 26.2 because...

I conducted a thorough search of this forum using the term 'battery drain after iOS update' and uncovered numerous posts detailing similar issues across various iOS updates. This suggests that iOS updates may not consistently be the root cause. Below are a handful of examples extracted from the search results:

• iPhone 14 Pro Max battery drain after iOS 17.0.1 update
• iPhone 6s battery drain after iOS update 15.7.1
• Re: Battery draining quickly on my iPhone 13 after iOS 18.5 update
• Battery Drain rate after iOS 16 update
• My iPhone 13 battery is draining fast after iOS 18.3.2 update
• Battery Draining after the ios 16.5 update
• Battery Draining after updating iOS 18.1.1
• Re: Battery drain after ios 15.6 update
• battery drain after ios 10 update
• Re: iPhone battery drain after updating to iOS 16.3