Apple is actively investigating the causes of excessive battery drain that appear to be related to iPhone OS 3.1. Since the update became available September 9, a number of users have reported the rechargeable battery seems to drain significantly faster than it did with iPhone OS 3.0.
In order to look into the problem, Apple has been contacting some users who posted about problems with battery life to Apple’s discussion forums and asking them to provide further details about their usage patterns. The questions ask about push e-mail, push notifications, WiFi, Bluetooth, and app usage—all things which long-time iPhone users know can affect battery life.