If you're running low on juice and just need basic functionality from your iPhone, try switching it to Low Power Mode to save power. Low Power Mode, which is also a new addition with iOS 9, tells your iPhone to cut down on certain features to lengthen its battery life. This means it’ll stop refreshing apps in the background, pushing email, and other tiny things in order to keep your battery going. Just head to Settings > Battery and toggle on Low Power Mode.