Ios 18.3.2 battery Drain on iPhone 16 pro

The battery drain you are experiencing is likely due to an app update and nothing to do with iOS 18.3.2. App updates in the background by default far more often than any iOS update and some of those app updates have ben seen to use more background processes on your phone, draining the battery, even when not in use.

Go to Settings > Battery, and scroll down to see the apps that have use the most battery in the last 24 hours. Meta has had some disastrous updates with a battery draining problem that affects multiple devices and OS versions. If fact the Google Support forums are flooded with the same battery draining complaint on Android devices as well. Most Meta apps have been updated 10 times in just the last month in an attempt to fix bugs and you would likely not even know it.

I agree to Force Restart your phone after an iOS update and don't micromanage your charging. Just turn on Optimized Charging and charge your phone all night, every night. If you never let it charge to 100%, it will never be able to recalibrate. Optimized Charging will learn your charging habits when done on a regular basis and only charge to 80%, until right before you normally take it off the charger will it will charge to the full 100%.