Apple has released the update iOS 15.4.1 and iPadOS 15.4.1 to address the battery drain bug that has troubled most of its users after updating to iOS 15.4
Through an Apple Support Tweet, a representative informed a customer complaining about battery issues that it was “normal for your apps and features to need to adjust up to 48 hours after an update.”
Thanks for reaching out! We’ll be happy to help. It’s normal for your apps and features to need to adjust up to 48 hours after an update.
Let’s have you reach out to us in a DM if this is still an issue after that time so we can help you look into this further.
— Apple Support (@AppleSupport) March 19, 2022
Additionally, the update also brings security fixes. To update your iPhone, simply enter the Settings, go to General, and hit Software update.