The N900’s battery life is fairly decent to start with, but you can get more out of each charge with a couple of simple tips:
1. Lower the phone display brightness and change the backlight time-out to 10 seconds. Also, disable touch-screen vibration and enable Power saving mode. Located in Settings -> Display.
2. Turn off the notification light. Settings -> Notification light.
3. Turn off all key and touch-screen sound effects. Settings -> Profiles.
4. Turn off Bluetooth. Settings -> Bluetooth.
5. Force wi-fi/WLAN to only connect manually. Settings -> Internet connections.
6. Change your wi-fi/WLAN transmission power to 10 mW. Settings -> Internet connections -> Connections -> (select access point) -> Edit -> Next -> Next -> Advanced -> Other -> Wi-Fi Transmission Power.
6. Close any running applications that aren’t necessary.
7. If the E-mail application is set to automatically update, increase the Update interval. E-mail application -> Settings.
8. If the RSS feed reader is set to automatically update, increase the Update interval. RSS application -> Settings.
9. Turn off the GPS and disable network positioning. Settings -> Location.