How do I fix battery drain issue on my iPhone 16 Pro Max?

Hello!

Please force restart your iPhone: Force restart iPhone - Apple Support

Try to remember to do this after every update, as it will help fix potential issues such as above normal battery drainage. Also know that after performing updates, your iPhone is performing multiple background tasks and clean up activities, so a slight decrease in battery life is normal for a day or two after updating.

You should charge your battery to 100%, every night, or whenever you feel the need to during the day. There is no need to micromanage your charging. The device already does that for you, and has lots of built in protection and sensors which protect the device from overcharging, overheating while charging, etc.

There are many misconceptions about battery charging out there, and I suggest you take a look at the following links so you get aquatinted with the proper way of charging your iPhone. (Spoiler: it’s as simple as charging it whenever you want to, and keeping it plugged in during the night)

👉 When to charge your iPhone or iPad - Apple Community (Must Read!)

👉 Maximizing the battery performance and lifespan of your iPhone. 

👉 iPhone Battery and Performance. 

👉 About the battery usage on your iPhone

Have a great day!

Most iOS updates require the OS to reindex your data on your device as part of its optimization process. This happens slowly when the device is on battery, but continues nonetheless - hence the battery drain. If you have a lot of data on the device, it takes long to finish the process.

That usually takes around 24-72 hours and then battery life goes back to normal.

Good luck!

Fully charge the device and observe the significant increase in its battery life. There no reason not to fully charge it.