Save power automatically by tapping Settings > battery saver. When Battery Saver is on, a small heart icon appears over the battery icon, and your phone does not automatically receive mail and calendar updates, update some live tiles, or allow apps to run in the background. 

You can also try the following:

Turn off services and functions that you do not use: 

  1. Close apps you are not using: Long press the back key to see the apps running in the background. Tap the app to open it and tap the back key to close it.
  2. Switch off location services: Tap Settings > location, and switch Location services to Off.
  3. Switch off Bluetooth: Tap Settings > Bluetooth, and switch Searching and discoverable to Off.
  4. Stop your phone connecting to games: Start Games app, then tap ... > Settings, and switch all relevant settings off. 
  5. Check which apps are running background tasks and block the ones you do not need: Tap Settings, swipe to applications, and tap background tasks. Tap the app you want to block, and tap block.

Change the frequency of certain events:

  1. Change your mail settings to retrieve mail items less frequently: On the start screen, open the mail account you want to modify, tap ... > Settings > synchronisation settings and change the setting for Download new content or set it to manual control. 
  2. Set your phone screen to switch off after a shorter time: Tap Settings > lock+wallpaper, and change the setting for Screen times out after.
  3. Stop your phone scanning for Wi-Fi networks: Tap Settings > WiFi, and uncheck the Notify me when new networks are found check box.

Other tips:

  1. Reduce screen brightness: Tap Settings > brightness, switch Automatically adjust to Off, and switch Level to low.
  2. Use a Wi-Fi connection to the internet or set your phone to use 2G (GSM) network only: Tap Settings > mobile network (or cellular) > Highest connection speed.
  3. Charge your phone until the phone battery level is 100%. To check phone’s battery level, go to Settings > Battery Saver > Remaining Battery Life.
  4. Use wired headphones, rather than the loudspeaker.
  5. Check that your apps are up-to-date: Go to Store (Marketplace). If there are updates available, tap Updates to update the apps.

If the battery keeps draining fast:

  1. Restart your phone by pressing and holding the Power and Volume Down keys simultaneously until the phone vibrates. Release and the phone will restart. After this operation, you may need to set the date and time on the phone (Settings > date+time).
  2. Out of date or invalid passwords for email and social media accounts affect battery life. Delete and re-create your account profiles by long tapping the relevant account profile in (Settings > email+accounts). If this fails, switch your phone to flight mode and reboot. Then delete your email profile, turn off flight mode and re-create your email. Apply this for all stalled account profiles (Mail Account which is set as Windows Live on the device cannot be removed manually).
  3. The battery may be wearing out and require replacing.