With the new GPS receiver and 3G radio sucking the life out of your iPhone 3G's battery like there's no tomorrow, you'll likely have noticed shorter battery life compared with the first-generation iPhone. If the iPhone 3G is your first foray in to the world of Apple phoning, then just accept that whatever battery life you manage to get is normal.
But, just because you have faster data speeds (enabling faster web-surfing) and real-deal GPS hardware tucked inside that glossy-backed iPhone 3G of yours, doesn't mean you have to live with shortened battery uptime. There are a few things you can do to try and increase the time between battery charges.
First off, you can disable your 3G data radio. That means you get slower web-surfing and data-speeds. You'll be limited to EDGE data access. But, that doesn't necessarily mean your web-surfing times will suffer all that much. iPhone 2.0 OS boasts improved Webkit performance that helps load websites faster than with previous versions of the iPhone Mac OS. You'll be surfing at slower speeds than if you had the 3G radio enabled, but you'll still be surfing at faster speeds than the original iPhone running iPhone 1.1.4 OS.
* Navigate to Settings>General>Network>Enable 3G and toggle "OFF'
Second, you can try to force-quit applications that may be running in the background and sucking precious electrons from your battery pack. Once started, most iPhone applications will continue to persist in an inactive state in the background. They wait for you to return to them, starting up lickity-quick in the same state that you left it in.
* Open up suspect applications (anything that you don't want persisting in the background) and hold down the "Home" (the only button on the iPhone's face) until the application quits. It takes a while, be patient.
Third, try resetting the iPhone. As with any computer, a quick system restart can solve most problems faster and easier than tracking down the specific issue.
* Hold down the Power/Sleep button located along the top-edge of the iPhone until you see the "Slide to Power OFF" prompt.
* Flick the slider to the right and let the iPhone shutdown.
* Press the Power button to turn on the iPhone
Lastly, you can try to reset your network settings. This can also resolve any signal strength issues, but will also wipe any stored WiFi passwords and settings. Use this as a last resort - not because its dangerous, but because it can be a hassle to re-enter all your WiFi passwords.
* Navigate to Settings>General>Reset and hit "Reset Network Settings"
