We start by talking about one of the most important features of iOS 5 which is Siri. If like your “personal assistant” you have the possibility to access Settings > General > Siri and from there you can turn off the option called Raise to Speak. What this does is invoke Siri when you lift the device to your face, but the thing is that many users have complained that it drains a lot of battery. If this option is turned off you can wake up Siri by pressing and holding the Home button.
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Although it might not sound that important, the auto-lock feature should be taken into consideration. Some users have mentioned that after making the update to iOS 5, the settings of the Auto-Lock had changed. An example would be that you have the device configured so it will auto-lock in one minute and after making the update this setting is changed to never which can cause a lot of battery drain. To fiddle with the setting for Auto-Lock you’ll have to go to Settings > General.
It is a known fact that pushing data to an iOS device has a negative effect on the battery so you might want to turn this off by going to Settings > Mail, Contacts, Calendar > Fetch New Data. Once you get there you’ll have to flip the switch called Push to off. After doing this, the device is going to fetch data according to the established interval of time: every 15min, 30min, 60min or manually. Selecting the latter option is going to preserve the most battery due to the reason that the data is going to be sent to device only whenever an application needs it. Keep in mind that you also have the possibility to select which of the accounts can push, if supported, and fetch. For doing this you will have to scroll down to the Fetch New Data’s screen and there select Advanced. Once you get there you will see that you’re able to modify the settings for each of the accounts that you use. With iCloud you can move data automatically between the device running on iOS and the cloud. It is indeed a great feature but it can drain a lot of battery. Access Settings and then iCloud to get to see what sorts of options are available. You might want to turn off automatic updates if you do not verify reminders, events and contacts on a regular basis. Another option that you will have to take into consideration carefully would have to be Photo Stream since if it is activated, every time you take a picture it will be uploaded to the cloud as well, meaning that it drains additional battery life. In a similar way, if Documents & Data is activated, more data is going to be sent to the cloud, causing a battery drain.
You might want to go to Settings - Notifications to switch off some of the ones which you can live without. In addition, lower the brightness of the screen to get more juice from the battery. As far as AirPlay is concerned, this needs a huge amount of battery so you might want to use it only when the iOS 5-running device is plugged in.