The new iPhone's brighter screen, GPS and 3G connectivity are nice, but you know what's nicer? Not running out of batteries half way through the friggin day. iPhone 3G battery life may or may not be shorter, even the geek gods at Ars don't have a definite answer. But chances are with the new apps and faster internet, you're using it a lot more often. Here's how to live with the iPhone's battery life while using it a whole lot.
1. Turn down the LCD. The new iPhone's screen is brighter, but you shouldn't be running this thing at full heat if you want to save battery power. I keep mine at 10% brightness. Change this under Settings -> Brightness.
2. Wi-Fi new network scanning off or Wi-Fi off. While you're not checking data for more than a few seconds at a time, I'd turn off Wi-Fi and in general, I'd turn off Wi-Fi scanning. It uses less power than EDGE or 3G but when you're not using your network connection, you might as well shut it down. Change this under Settings -> Wi-Fi. Same goes for Bluetooth.
3. Toggle off 3G til ready. Here's something I wish Apple had automatically managed. I use 3G for browsing, youtube, app store purchases when not around a computer, or during important calls. For all other uses, including email, weather checking and twitter, etc, I use EDGE. This setting is under Settings -> General -> Network.
4. Turn off Vibrate in Games. Playing a game with vibrate happening frequently is an unnecessary battery suck. If you can turn it off, turn it off.
5. Limit use of A-GPS tracking. GPS tracking is still pretty useless after you've gained your bearings, since there isn't a turn by turn navigation mode for driving. I exit out of maps once I've got the directions in my mind, and if I lose myself again, I just start maps up once more.
6. Buy Apps and Songs in iTunes. You can buy songs over Wi-Fi or Apps over 3G, but that doesn't mean you should. I'd recommend buying Apps at your computer if you can help it, and syncing them to your iPhone instead. As an added bonus, you'll be picking up a charge while you're tethered to your computer.
7. Set the Autolock to 1-minute. The iPhone's autolock is good at shutting off the screen if you forget to when placing it in a pocket, purse or just tossing it on a table after a call. I set mine to the most aggressive, 1-minute, but there are times where I set it to 2-minutes. This setting is under Settings -> General -> Autolock.
8. Use programs with 3D less often. Not surprisingly, I've noticed that when I play games rendering 3D, battery life drops. Using the graphics chips more intensely will crank up power usage, but maybe the drain is also because of the nature of gaming: Unlike email or browsing, gaming is a full time, full attention endeavour that also keeps the cpu, gpu and lcd going full time. (I'd like to think this is a more useful tip than "don't use your iPhone" but maybe it's not something you can avoid if you're a gaming addict.)
9. Set Push to Off, and Set Fetch Time. Push email isn't that useful for me because I know I'm getting emails all day long and that I have to be checking all the time. Push does use more juice than the fetch mode, which checks for calendar, contact and email syncing at set intervals of 15 minutes to an hour. I set mine to 1 hour unless I'm out of the office. If you seldom update your contacts and calendars, you might even be better off syncing by cable to iTunes, while you pick up a charge.
10. Stay Juiced. If you're at computer or in a car, you should try to use a cigarette adaptor or USB cable to pick up a few minutes of charge. Every bit helps!
These tips also apply to a first generation iPhone running OS 2.0.