iPhone 16 Pro battery drains extremely fast even without use

Your phone has a lot of housekeeping over night, it is never idle.

So do NOT go to bed unless your phone is on charge all night. Start will 100% when you get up, then see how it fares.

If you really want to test your battery overnight, charge it to 100% at bed time then take it off charge, and power it off

Turn it back on in the morning and your battery should lose only about 3% while powered off, if it loses as much as before then the battery is faulty.

Troubleshooting a Draining iPhone Battery:

I. Update your iPhone iOS:

There may be some bug fixes here and about, and installing an update is what this is all about. iOS26.1 is the most-recently released iOS version that is compatible with your iPhone model(iPhone 16 Pro), as of this reply. So, update to it, if not done so, already.

First, see if an Update is Available:

1. Go to: Settings
2. Tap: General
3. Tap: About
4. Verify: iOS 26.1 is shown.

If so...

1. Back Up First:

IMPORTANT: If you have an option to update, however, then be certain you backup your iPhone first. That way, you will have something to restore your iPhone from should anything go wrong with the update

then...

2. Proceed with the Update:

You can update from within the iOS, itself, or through a computer, or Cellular.

• Update your iPhone Using a Computer - User Tip
• Use an iPhone 12 or later, that is using 5G, in order to update over Cellular - User Tip

Links that may help...

II. Troubleshooting the Battery:

• iPhone Battery and Performance - Apple Support

• Charge and Monitor the iPhone Battery - Apple Support

• About the Battery Usage on your iPhone - Apple Support

• About Optimized Battery Charging on your iPhone - Apple Support

• If you see "Your iPhone Battery may Need to be Serviced" - Apple Support

• Use Low Power Mode to Save Battery Life on your iPhone - Apple Support