Advanced Battery Saver - Free

Advanced Battery Saver is an app that saves your battery usage by disabling certain phone features that you do not require when the screen is off.

Sometimes other apps will keep these features, like WiFi, running even though the Android sleep policy tells it to sleep.

There are many advanced features:
1) Telling the WiFi to awaken every 30 minutes. (*)
2) Waiting a set time before disabling features. (*)
3) Activating at certain battery levels (*)
4) Turning off mobile data
5) Auto Airplane mode. Great for Tablets.

(*) Some advanced features are only available for a week in the free version.