Press the power key 
, then select Turn power saving on. To switch power saving mode off, press the power key , then select Turn power saving off.
If it seems you're always looking for a charger, there are steps you can take to reduce the power consumption of your phone.
Always charge the battery fully.
When power saving mode is on, phone settings, such as Network mode and the screen saver, are optimised.
Press the power key , then select Turn power saving on. To switch power saving mode off, press the power key , then select Turn power saving off.
Press and hold the menu key, swipe until the app you want to close is shown, then select 
.
Mute unnecessary tones, such as key tones.
Use wired headphones, rather than the loudspeaker.
Change the length of the time-out period after which the phone screen switches off.
Select Settings and Phone > Display > Light time-out.
Select Settings and Themes > General.
To change the wallpaper, on the home screen, select 
> Change wallpaper.
Select Settings and Phone > Display > Brightness.
Select Settings and Themes > Screen saver > None.
If you are listening to music or otherwise using your phone, but do not want to make or receive calls, switch to the offline profile.
Set your phone to check for new mail less frequently.
Use a Wi-Fi connection to connect to the internet, rather than a mobile data (GPRS or 3G) connection.
If your phone is set to use both GSM and 3G networks (dual mode), the phone uses more power when searching for the 3G network.
Swipe down from the notification area, then select the mobile network and Network mode > GSM.
Swipe down from the notification area, then select 
.
Swipe down from the notification area, then select 
.
To close the mobile data connection, swipe down from the notification area, then select 
.