Here are 14 tips to help you extend your iPhone battery life.
1. Turn on Auto-Brightness
The iPhone has an ambient light sensor that adjusts the brightness of the screen based on the light around it (darker in dark places, brighter when there's more ambient light) to both save battery and make it easier to see. Turn Auto-Brightness on and you’ll save battery because your screen will need to use less power in dark places.
Find it in the Settings app -> Brightness & Wallpaper -> Auto-Brightness On
2. Reduce Screen Brightness
You can control the default brightness of your iPhone screen with this slider. Needless to say, the brighter the default setting for the screen, the more battery it requires. Keep the screen dimmer to conserve more of your battery.
Find it in Settings -> Brightness & Wallpaper
3. Turn Bluetooth Off
Bluetooth wireless networking is especially useful for cell phone users with wireless headsets or earpieces. But transmitting data wirelessly takes battery and leaving Bluetooth on to accept incoming data at all times requires even more juice. Turn off Bluetooth except when you’re using it to squeeze more juice from your battery.
Find it in Settings -> Bluetooth -> Move Slider to Off
4. Turn Off 3G/4G
The iPhone 3G and later models can take advantage the speedy 3G and 4G LTE cellular phone networks. Not surprisingly, using 3G, and especially 4G LTE, requires more battery life to get the quicker data speeds and higher-quality calls. It’s tough to go slower, but if you need more battery, turn off 3G or LTE and just use the older, slower networks. Your battery will last longer (though you’ll need it when you’re downloading websites more slowly!).
Find it in Settings -> General -> Cellular -> Slide Enable 3G to Off on some models or Enable LTE to Off on the iPhone 5 or newer
5. Keep Wi-Fi Off
The other kind of high-speed network that the iPhone can connect to is Wi-Fi. Wi-Fi is even faster than 3G, though it’s only available where there’s a hotspot (not virtually everywhere like 3G). Keeping Wi-Fi turned on at all times in hopes that an open hotspot will appear is a sure way to drain your battery life. So, unless you’re using it right this second, keep Wi-Fi turned off.
Find it in Settings -> WiFi -> Slide to Off
6. Turn Off Location Services
One of the coolest features of the iPhone is its built-in GPS. This allows your phone to know where you are and give you exact driving directions, give that information to apps that help you find restaurants, and more. But, like any service that sends data over a network, it needs battery power to work. If you’re not using Location Services, and don’t plan to right away, turn them off and save some power.
Find it in Settings -> Privacy -> Location Services -> Slide to Off
7. Turn Data Push Off
The iPhone can be set to automatically suck email and other data down to it or, for some kinds of accounts, have data pushed out to it whenever new data becomes available. You’re probably realized by now that accessing wireless networks costs you battery life, so turning data push off, and thus reducing the number of times your phone connects to the network, will extend your battery’s life. With push off, you’ll need to set your email to check periodically or do it manually (see the next tip for more on this).
Find it in Settings -> Mail, Contacts, Calendar -> Fetch New Data -> Slide to Off
8. Fetch Email Less Often
The less often your phone accesses a network, the less battery it uses. Save battery life by setting your phone to check your email accounts less often. Try checking every hour or, if you’re really serious about saving battery, manually. Manual checks means you’ll never have email waiting for you on your phone, but you’ll also stave off the red battery icon.
Find it in Settings -> Mail, Contacts, Calendar -> Fetch New Data -> Select Your Preference
9. Auto-Lock Sooner
You can set your iPhone to automatically go to sleep – a feature known as Auto-Lock - after a certain amount of time. The sooner it sleeps, the less power is used to run the screen or other services. Try setting Auto-Lock to 1 or 2 minutes.
Find it in Settings -> General -> Auto-Lock -> Tap your Preference
10. Turn off Equalizer
The iPod app on the iPhone has an Equalizer feature that can adjust music to increase bass, decrease treble, etc. Because these adjustments are made on the fly, they require extra battery. Turn the equalizer off to conserve battery. This means you'll have a slightly modified listening experience - the battery savings might not be worht it to true audiophiles - but for those hoarding battery power, it's a good deal.
Find it in Settings -> Music -> EQ -> Tap off
Source: http://ipod.about.com/od/iphone3g/tp/iphone-battery-life.htm
