Battery drainage (iPhone 16 pro max)

Did you also try to reset the iPhone to factory settings, in case the iOS software caused the issues?

To rule out defective data from the backup, set it up as a new device and test the battery life.

Restore your iPhone, iPad, or iPod to factory settings using a computer - Apple Support

If the battery life is back to normal, restore from the latest backup and check the battery life again.

Did you check in the settings for Battery, which apps are using most of your battery life?

Did you already force restart your iPhone after the latest update?

Force restart iPhone - Apple Support

MichaelSamirGhaly wrote:

Sure checked the settings and also the customer support checked it by screen sharing , every apps use a huge amount of power , when I was calling the customer support they noticed that the battery drained 8% in that call.

Also I did force restart to as per the customer support recommendation , but there’s no difference

That is not what ingo suggested. They suggested erasing back to factory settings.

also see this The last update killed my battery! - Apple Community

"Battery drainage (iPhone 16 pro max): I bought my phone 3 months and 7 days ago and I used to charge the phone once a day and with light use it might last for 1.5 day , but suddenly the battery performance drained like crazy as it lasts for around 7-8 hours with very light use , my phone up to date iOS 26.1 , I use the original charger and original cable.[...]"

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Troubleshooting Stalled Uploads:

A. Close All Apps:

Try closing all apps, and then seeing if this all goes away. Something is likely running in the background. Find Out Here: Close an App on your iPhone or iPod touch - Apple Support

B. Use a Different LAN:

If you are using a P LAN (Public LAN), then you may be consuming too much data, and you are being stalled as a user.

C. Clear Internal Space:

See if there is lots of space being taken up --if it is too-highly consumed, then processes will become slower. So, clear what need be (System Daya can overload sick for unknown reasons, now iPhone or not). SEE MY Two User Tips:

• How to Clear Space from your Mobile Device, and What to Clear: - User Tip
• How to Clear "System Data" in your iPhone's Storage: - User Tip

Edit: (System Data overload quick for unknown reasons,)