Tip: Improving battery performance on iOS devices
Is your battery life declining suddenly on your iPhone or iPad? Perhaps reconsider your push notification settings. And then there's a hard reset.
Developer Scott Gruby writes on his blog that his battery life suddenly began fading on his iPad. He said he restarted the device, which is an interesting suggestion. http://blog.gruby.com/2011/01/30/mystery-of-poor-ipad-battery-life/
As far as I understand, the difference between the usual iOS "slide to turn off" and the hard restart is similar, respectively, to the Mac's shutdown command (clicking Shutdown or Restart... under the Apple menu) and holding down its power button until everything goes clunk. The hard reset is abrupt but may trigger some startup diagnostics. In either case, caches are flushed and processes are restarted.
Not everyone agrees that a hard reset is a best practice. Apple's Support site says it should only be done if the iPad/iPhone/iPod "is no longer responding." But these Unix machines stay on for such a long time, it may be useful as Gruby suggests to perform one every now and again.
[To reset your iPad, press and hold down the Home and Sleep/Wake buttons until the Apple logo appears. This will take as much as 10 or more seconds.]
Gruby also suggests checking the settings on mail accounts and push notifications. If you can do without, your battery life will be extended. A certain level of battery drain from the notifications may be acceptable, Gruby suggests, in a device you regularly plug in overnight but not so much in an iPad.
The second thing I did, which is kind of a “duh” is I turned off push notification, removed 1 email account, and switched to checking data every 30 minutes. The push notification system keeps a connection constantly open with Apple’s server so that if a notification comes in, it can be sent down the already open pipe. This, of course, takes power to maintain this connection. However, I leave push on for my iPhone and I don’t see a huge drop in battery life. There are, of course, many differences such as the size of the battery and I charge my iPhone every night.