Battery drain

Increased battery utilisation can be expected to occur immediately following a system software update - as many background housekeeping tasks (such as re-indexing) will be running. Normal battery performance can be expected to return within a few days.

If your battery utilisation is exceptionally high after applying an update, a process may have stalled. In such circumstances a forced-restart will often clear the issue:

• On an iPad with a Home button: Press and hold the top button and the Home button at the same time. When the Apple logo appears, release both buttons.
• On other iPad models: Press and quickly release the volume up button, press and quickly release the volume down button, then press and hold the top button. When the Apple logo appears, release the button.

If you continue to experience difficulties, you may need to seek assistance directly from from Apple Support. If needed, you can contact the Support Team using the Get Support link at top-right of this page. Alternatively, you can initiate and manage your support cases using the excellent Apple Support App. If not already installed on your iPad, the App can be downloaded from the App Store:

https://apps.apple.com/gb/app/apple-support/id1130498044

You might also visit the Genius Bar at your local Apple Store or Apple Authorised Service Provider (AASP) - where the technicians will be able to test and assess your iPad:

Genius Bar Reservation and Apple Support Options - Apple

I am having a similar problem with excess battery drainage on two iPhone 12 pro maxes, an iPad Pro, and an iPad Pro second generation. I am using AT&T in St. Louis, Missouri. My problem started after installing iOS 15.6.1 and updating my apps. I am getting as much as 3.5 GB per day of "Settings > Cellular> System Services> Push Notifications", and my (otherwise healthy) battery requires unusually frequent recharging. I turned off all app Notifications (except Phone and Messages), and all background app refresh. Also, at Apple Support's suggestion, in Privacy>Location Services>System Services, I turned off several location related System Services (such as Location Based Alerts). This has not worked to stop the Push Notification data hemorrhage. Phone calls to Apple Support on 8/21/22 and 8/22/22 also failed to solve the problem. So far, the only way to stop the Push Notifications is to turn off Cellular Data. Even after stopping Cellular Data, I have noticed unusually rapid battery depletion if Wi-Fi is turned on. Check your Push Notifications, and see if that is part of your problem. If so, perhaps Apple Support can help you.

I want to update my iPhone to 15 version