BatteryFu (pronounced Battery-Foo, like in Kung-Fu) extends battery life (and lowers data usage) by changing always-on mobile/wifi data to periodic sync (meaning it disables your mobile data and/or Wifi, then checks your accounts every X minutes). This also provides a way to manage your data usage.
BatteryFu is also great for tablet use to keep accounts sync'd even when the tablet is in sleep/standby. Normally accounts won't sync due to WiFi going to sleep (see "WiFi sleep policy").
*NOTE*: BatteryFu requires root on Android 5+ to toggle mobile data.
BatteryFu is open source software.
* Lean and fast (see download size!)
* Work for all networks (CDMA/GSM) from Gingerbread up
* Notification icon: lets you switch modes even while inside another app.
* Data while screen is on, with screen off delay
* Data while charger is plugged in
* Pre-defined modes: Travel mode, Online mode, Offline mode, Night mode, etc.
* BatteryMinder shows battery stats, like usage during screen off, kernel wakelocks, etc.
* 3rd party app support (using intents) so that you can control BatteryFu from your own app.
* Open source
Tips for even better battery life:
* Select "2g networks only" in Android settings
* Turn off "Network notification" under Wifi settings
* Uninstall apps if your phone is running out of RAM (e.g. slow to get to homescreen or switch apps)
* If your battery life is out of control, reset phone to factory defaults, install BatteryFu and be amazed! Then slowly re-install some apps
* Do not put apps on SD card if they run in the background. SD card access drains battery.
See website for more information, if you have problems, or would like to donate. Email for support, I don't check comments.
Contribute issues/source code here: https://github.com/tobykurien/BatteryFu