There’s nothing worse than your iPhone running out of juice at an inopportune time. Starting in iOS 9, there’s a Low Power Mode that’s offered to you when the remaining battery charge drops below 20%, and it’s automatically disabled once the charge rises to 80%. You can also enable Low Power Mode manually in Settings > Battery if you anticipate a day when you might run out of power. When you’re in Low Power Mode, certain features are disabled, including automatic app downloads, background app refreshing, email fetching, iCloud syncing, and some visual effects. It also reduces display brightness and optimizes device performance to conserve as much power as possible. When Low Power Mode is on, the battery icon at the top of the screen turns yellow.