It’s possible to save power when using Maps to navigate in a car. It’s an obvious trick once you know about it, and easy too.

When you’re navigating with the Maps app, you’re probably used to it chewing through battery life. Even on a full charge my iPhone 5 doesn’t last more than 2-3 hours when navigating.

To eke out extra life, just press the Sleep button (top of the phone), once you’re on your way and are on a long stretch before the next turn/navigation point (i.e. on a freeway for 50 miles). The screen will blank, but the navigation will continue. The phone will briefly wake 10 miles from your next turn/navigation point, to tell you about it, and will wake 2 miles from it and stay awake until you get past it.

To switch back to non-power-saving mode, just swipe as usual to wake the phone.

To be honest this doesn’t save a huge amount of battery life in my tests, but it’s better than nothing. For long journeys,you really need a USB power sour …

Source: Mac OSX Hints