A lot of people are complaining the battery is draining fast after they updated their iPhone/iPod to the new operating system iOS 4. If you are one of them, here are some tips and tricks for you to enhance and increase the battery life in iPhone. In most cases you will see the problem is completely resolved after using these tips.
Apply these steps one by one and check the performance of battery after each step:
Step 1: After upgrade to iOS 4, let the battery run down to shut down and recharge it full again. (Important)
Step 2: Check the Internet Tethering in the Settings>General>Network>…. If you see the internet tethering is constantly “working” to connect, switch off the wifi and then go back to check the internet tethering in settings. If it is loaded to the “set up internet tethering” mode rather than continuously spinning its wheels, go back and turn wifi on and check again. It will be okay now (not constantly running).
You can use this method too to turn off tethering. Go to tethering screen and wait until it connects with ATT (You will be told to contact ATT if you want to add tethering) and hit the “Cancel” button to stop the tethering activity. (Important)
Step 3: A mail app can also cause fast drainage if it tries to connect to (Google’s) exchange server over and over again. Turn it off. (Important)
Step 4: Turn off all Location Services.
Step 5: Turn off Push, Wifi and bluetooth.
Step 6:Do a hard reset by holding Home button and top button. (Important)
Step 7: If the problem is not resolved yet, uninstall all those apps which use external services i.e., all apps which use GPS, WiFi, bluetooth etc. Most of the apps have not been either upgraded or optimized for iOS4, so a rogue application can cause the problem.
If the problem persists, contact the Apple, or wait for next iOS 4.1 (iOS 4.01) update, or you can also downgrade your iPhone to previous version.