Apple is touting its battery improvements with iOS 9, promising that an iPhone under typical use will last for around an hour longer than before. The under-the-hood changes will be delivered effectively seamlessly, Apple said. However, that’s not the only boost in battery life that iOS 9 can deliver, if you flick the right switch.

A new option will activate a more frugal mode, which Apple says will deliver up to a further three hours on top of that initial hour-long improvement.
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