If you just updated to iOS 11 and noticed that your battery life is no longer as good as it used to be, there are a few things you can do to make sure your phone makes it through the day.
It may take a few days for your iPhone to optimize itself to get used to your day to day life. Use your iPhone like you normally do, and allow it a few days to fully reindex and cache everything, and that may just do the trick.
Battery Settings - Under Settings > Battery, you can see all the apps that drain your battery. If you notice apps you do not use in this list, make sure you delete them. For ones that are draining a lot of battery, try changing the settings on them to optimize your battery life. Finally, sometimes, a suggestion will show up on things to try to do to increase the battery life.
Disable Bluetooth - If you don't use bluetooth, disabling it can save you some battery life. New to iOS 11 is that bluetooth does not turn off when disabling through the control panel. It will just show not connected. In order to fully disable it, you will need to disable it in Settings.
Enable Reduce Motion - App launching animations and parallax effects on the home screen can be disabled to save battery life further. Go to Settings > General > Accessibility > Reduce Motion
Location Services - Many of the apps use location services. This can drain the battery tremendously. To access location services, go to Settings > Privacy > Location Services. You can Disable them or set it to While Using.
Disable Auto-Brightness - Auto-brightness is a great feature, but it may amp up the brightness when it is not necessary. It is easy to change the brightness through the control center, so auto-brightness is not needed. To disable it, go to Settings > General > Accessibility > Display Accommodations.
Disable Raise to Wake - Raise to wake is very convenient, but it may cause the iPhone to come to life more often than necessary. To disable, go to Settings > Display & Brightness.
Disable Notifications - Notifications are useful, but not needed for every app. Every time a notification comes in, it wakes up the phone briefly. To disable, go to Settings > Notifications and disable the apps you do not need notifications from.
Siri Suggestions - Siri suggestions use your location and visited places to provide this feature. This can drain the battery. If you do not use this feature, you can disable it by going to Settings > Siri & Search.
iCloud - Backing up your items is important, but it is best to do it when you are at home or somewhere that provides a power source, since some items, like photos, can take a lot of power and time. To change your iCloud settings, select your name in Settings, then iCloud. Disable the things you don't want to store on iCloud.
iTunes & App Store - Downloading is one of the biggest battery drainers on your phone. To keep from using up your data and power, you can go to Settings, select your name, and then iTunes & App store and disable Use Cellular Data and Automatic Downloads.
Fetch New Data - Updating your mail, calendar, and iCloud is useful, but you do not have to do it constantly. To adjust the interval, go to Settings > Accounts & passwords > Fetch New Data. Change the interval to something further apart to conserver battery life.
Data being sent to Apple - It is great to send your information to Apple, so they can provide us with the best products, but if you do not wish to do this and conserve battery life, go to Settings > Privacy > Analytics and disable it.
Advertising - There is no way to turn off advertising, but you can limit it by going to Settings > Privacy > Advertising - Enable Limit ad tracking.
Disable Hand off - Hand off is a nifty feature if you have other Apple products, but if you do not, go to Settings > General > Handoff and disable it.
David, AT&T Community Specialist
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After updating IOS 11 on my iPhone 7 plus, I have noticed a problem on battery life. Which I found had a lot of tips on a thread from Google and I solved the problem. If you have this problem, please visit this thread and resolve your problem.