Battery keeps dying

Same here. It lasts like four hous, even without using Safari... 3g here

Try restoring the iPhone and setting it up as a New Device.

Also, take a look at the tips on the Apple Batteries webpage

Thanks for the reply. Now, setting it up as a NEW DEVICE will erase everything, won´t it?

Tif wrote:
Thanks for the reply. Now, setting it up as a NEW DEVICE will erase everything, won´t it?

Yes. It sounds like something that will be necessary though because you already updated, which would have also restarted the iPhone, and the battery drain is unusually quick.

You can always restore the iPhone in another user account or archive the backup, so you have the option to revert to that backup.

From http://support.apple.com/kb/HT3828:
"If you choose to set up as a new iPhone or iPod, first transfer your purchases and other data, then back up any important backups of that device you want to retain from the backup folders listed above. iTunes only retains one sync-generated backup per device, and the first sync after setting up as new will replace your previous backup. If you change your mind and want to restore to your previous state, you will have to do so from a backup that you have retained through your periodic backup routine. If you have Mac OS 10.5.5 or later and use Time Machine, Time Machine may back up your backup. Copies of a backup marked with a date and time stamp created by selecting to "Restore from the back up of" are retained by iTunes and not overwritten. For an example of a backup with the date and time stamp in the device name, see the picture below in the Deleting a Backup section."