High battery utilisation is not unusual following a system software update - as background tasks, such as re-indexing the file system, typically take several days.
If battery utilisation is excessive, one or more forced-restarts of your iPad may resolve the problem:
- 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 the problem cannot be cleared, it may be necessary to restore your iPad - initially to Factory Settings - and then from your iCloud or iTunes backup.
Restore your iPhone, iPad or iPod to factory settings – Apple Support
Restore your iPhone, iPad, or iPod touch from a backup - Apple Support
You’ll need access to either a PC (with iTunes installed) or a Mac (with iTunes or Finder - as appropriate for the installed version of MacOS).
Download and use iTunes for Windows – Apple Support
Update to the latest version of iTunes – Apple Support
Use of a PC or Mac computer is unavoidable. If you don’t have access to a suitable computer of your own, that of a helpful friend or family member will suffice. Alternatively, the technicians at the Genius Bar of your local Apple Store or Apple Authorised Service Provider (AASP) will be delighted to assist.