How to Fix the Battery on an iPhone
A fast-draining battery on your iPhone don't always mean a faulty battery. Battery problems have been reported after operating system updates on several versions of the iPhone. At other times, battery issues have surfaced when certain applications are downloaded or upgraded. There are steps you can take to determine whether the operating system or application is draining your battery.
Disable the Push feature used by your email accounts. Tap the "Settings" icon on your iPhone's home screen. Tap into "Mail, Contacts, Calenders" and then tap into "Fetch New Data." Disable the Push feature, then reboot your iPhone. If the battery issue is resolved, return to the "Fetch New Data" area and set up the Fetch feature to fetch your mail, while leaving Push disabled.
Turn off the Location service. Tap the "Settings" icon on your iPhone's home screen, then tap "General" and finally tap "Location Services." Turn off location services for all applications, then reboot, and test your phone to determine if the battery is still draining too fast. If not, you may return to the "Location Services" area and enable location services for one application at a time, then test the phone until you determine which application is draining the battery.
Disable Internet Tethering. Tap the "Settings" icon on your iPhone's home screen, then tap "General," then tap "Network" and finally tap "Internet Tethering." Tap "cancel" to cancel any current attempts by the iPhone to tether, and then turn off tethering. Reboot your phone and test the battery.
Close any Safari windows left open in the background. Tap the "Safari" icon, then close each Safari window individually by tapping the red X at the top left of each minimized Safari window. Test the battery, and if closing Safari windows has resolved the problem, remember not to leave Safari windows in the background in the future.
Test your applications to determine if one or more applications are draining the battery. Back up your iPhone in iTunes on your desktop computer, then delete one or more applications from your phone. If you installed new applications shortly before experiencing battery trouble, you may wish to start by deleting those applications first. After each application has been deleted, test your battery life. If an application has been draining the battery, do not install it again. Restore your other applications from iTunes after you have tested the battery.
Recondition your iPhone battery. Allow your battery to run down to the point where your iPhone automatically shuts itself off, then fully recharge your phone. If reconditioning your iPhone battery helps, you may want to invest in an iPhone app that will run battery reconditioning cycles for you.