Tips on Maximizing Battery Life on Android Phones in the Field
From Guardian Project Wiki
- Turn "Airplane Mode" on your phone when you are going underground, into areas of poor coverage, and whenever else you don't need connectivity
- When using Wifi, you can set your device to "Airplane Mode" so that the GSM/CDMA/Phone radio is turned off.
- Set your mobile network to use "2G networks" only, unless you absolutely need 3G speeds