15.4.1 in battery drain issue

Hey there ,

It is assumed that an update has solved the battery drain problem. If you are still facing this problem, you should Contact Apple for support and service - Apple Support

But before you do that go to Settings > Battery > battery using by app , Check out the applications that consume the battery heavily. If there is nothing that consumes the battery heavily, there may be a technical problem Or if you replace the battery by a store that is not approved by Apple, it may be non-native and may cause the battery to drain and if your battery health is 80% or less you need to replace it!

and also see this article’s might help you:

• 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