How do I avoid my iPhone 16 Pro Max quick battery drain?

A draining feature is the always on display. Turn it off by following these steps.

1. Open the Settings app.
2. Tap Display & Brightness.
3. Select Always On Display.
4. Enable or disable the switch for Always On Display as needed.
5. You can also choose to show or hide the Lock Screen wallpaper and notifications on the Always-On display.

Additionally, you can go to settings , battery. To find what is taking up the most battery

After you first setup an iPhone, it must carry out several background tasks including indexing to complete. This can drain additional battery. Give it a few days and it should be back to normal.

All rechargeable batteries are consumable components that become less effective as they chemically age.

Recent software updates can accelerate that process by adding features that consume more power.

As lithium-ion batteries chemically age, the amount of charge they can hold diminishes, resulting in shorter amounts of time before a device needs to be recharged.

Apple won’t replace the battery until it reaches 80% capacity.

Li Ion (Lithium Ion) batteries have recharging capabilities; however there are limits.

I recommend to slow charge your iPhone to maximize the charge capacity, battery health and efficiency. ⚡️🔋

NOTE:

Capacity loss in standby applications is largely determined by temperature.

Charge above -30°C and discharge below 55°C for best results.

Battery Performance Tips:

• iPhone Battery and Performance.
• Check battery health and usage.
• Optimized Battery Charging.
• Maximizing Battery Life.
• Use Low Power Mode.
• About battery usage.
• Show battery percentage.

Click ▶︎ iPhone User Guide. 📖

Good luck! 👋🏼😉

See this.

Batteries - Maximizing Performance - Apple