Apple recently announced the software update for iOS 6.1.3. Several users have reported battery drain issues after they have updated to iOS 6.1.3, meaning that their device (iPad, iPhone, or iPod) depletes its battery more quickly than it should according to Apple’s specs. You may want to try the following tips to fix your poor battery problem. Here are some things you can try.
Following solution was provided, courtesy of fellow Apple Support Communities member Markbob917:
1. Go to settings.
2. Mail, contacts, calendars.
3. Go into iCloud and turn all switches to OFF one by one make sure you save all to iPhone though not just delete.
4. Then go to each other mail account and repeat this procedure again making sure you select keep on iPhone not the delete option.
5. Once they’re all turned to off check your calendar to see if everything is missing off it and then you need to do a hard reset by holding the home button and the on/off button until the phone turns itself off.
6. Once it’s come back on go back into settings and mail and turn each switch (or each you want) back to ON.
7. Then make sure all your apps are closed lock the phone and leave it for 30 mins and then check the battery hopefully if like mine it shouldn’t of dropped at all.
You can improve your battery life significantly by changing a few simple settings (see this article and this). Please read this article related to prolonging your battery’s life. Also, read these suggested ways to maximize your iPod, iPhone or iPad battery life provided by Apple.