The battery life of the iPhone is either terrific or terrible, depending on your point of view—and which model you have.
If you were an optimist, you’d point out that when these phones are using AT&T’s 3G network, they get longer battery life than any other 3G phone. You’d also extol the iPhone 4’s even better battery, which goes about 16 percent longer than the 3GS’s.
If you were a pessimist, you’d observe that the 3G/3GS and 4 models get only 5 hours and 7 hours of talk time, respectively, compared with 8 hours on the original iPhone. And that if you’re not careful, you might not even make it through a single day without needing a recharge.
So knowing how to scale back your iPhone’s power appetite could come in extremely handy.
The biggest wolfers of electricity on your iPhone are its screen and its wireless features. Therefore, these ideas will help you squeeze more life out of each charge:
- Dim the screen.
In bright light, the screen brightens (but uses more battery power). In dim light, it darkens.
Note: This works because of the ambient-light sensor that’s hiding behind the glass above the earpiece. Apple says it experimented with having the light sensor active all the time, but it was weird to have the screen constantly dimming and brightening as you used it. So the sensor now samples the ambient light and adjusts the brightness only once—when you unlock the phone after waking it.
You can use this information to your advantage. By covering up the sensor as you unlock the phone, you force it into a low-power, dim-screen setting (because the phone believes it’s in a dark room). Or by holding it up to a light as you wake it, you get full brightness. In either case, you’ve saved all the taps and navigation it would have taken you to find the manual brightness slider in Settings.
- Turn off 3G.
This is the biggie. If you don’t see a 3G icon on your iPhone’s status bar, then you’re not in a 3G hot spot, and you’re not getting any benefit from the phone’s battery-hungry 3G radio. By turning it off, you’ll double the length of your battery. The iPhone 3G/3GS goes from 5 hours of talk time to 10; the iPhone 4 goes from 7 hours to 14!
To do so, from the Home screen, tap Settings→General→Network→Enable 3G Off. Yes, this is sort of a hassle, but if you’re anticipating a long day and you can’t risk the battery dying halfway through, it might be worth doing. After all, most 3G phones don’t even let you turn off their 3G circuitry.
Tip: Turning off 3G has another huge, huge benefit: It forces the phone to use AT&T’s older, but much larger, non-3G cellular network. It’s like switching from AT&T to Verizon on a per-call basis. Often, the result is that you can now place calls when you couldn’t before. Next time you’re getting a lot of dropped calls, remember this trick—and marvel.
- Turn off WiFi.
If you’re not in a wireless hot spot, you may as well stop the thing from using its radio. From the Home screen, tap Settings→Wi-Fi→Off.
Or at the very least tell the iPhone to stop searching for WiFi networks it can connect to.
- Turn off cellular data.
This option is new in iOS 4. It turns off the cellular Internet features of your phone. You can still make calls, and you can still get online in a WiFi hot spot.
This feature is designed for people who have signed up for one of AT&T’s capped data plans, meaning you have to monitor how much Internet data you’re using each month. If you discover that you’ve used up almost all of your data allotment for the month, and you don’t want to go over your limit (and thereby trigger an overage charge), you can use this option to shut off all data. Now your phone is just a phone.
- Turn off the phone, too.
In Airplane mode, you shut off both WiFi and the cellular radios, saving the most power of all.
- Turn off Bluetooth.
If you’re not using a Bluetooth headset, then for heaven’s sake shut down that Bluetooth radio. In Settings, tap General and turn off Bluetooth.
- Turn off GPS.
If you won’t be needing the iPhone to track your location, save it the power required to operate the GPS chip and the other location circuits. In Settings, tap General and turn off Location Services.
- Turn off “push” data.
If your email, calendar, and address book are kept constantly synced with your Macs or PCs, then you’ve probably gotten yourself involved with Yahoo Mail, Microsoft Exchange), or MobileMe. It’s pretty amazing to know that your iPhone is constantly kept current with the mother ship—but all that continual sniffing of the airwaves, looking for updates, costs you battery power. If you can do without the immediacy, then visit Settings→Mail, Contacts, Calendar→Fetch New Data; consider turning off Push and letting your iPhone check for new information, say, every 15, 30, or 60 minutes.
- Turn off the screen.
On the iPhone 3GS and iPhone 4, you can actually turn off the screen, rendering it totally black and saving incredible amounts of battery power. Of course, you now have to learn the VoiceOver talking-buttons technology to navigate and operate the phone.
Last battery tip: Beware of 3-D games and other add-on programs, which can be serious power hogs. And turn off EQ when playing your music.
Learn more about this topic from iPhone: The Missing Manual, 4th Edition.
The new iPhone 4 and iPhone 4.0 software have arrived, and New York Times tech columnist David Pogue is on top of it with a thoroughly updated edition of iPhone: The Missing Manual. Each custom-designed page helps you use your iPhone for everything from web browsing to watching videos. The iPhone is packed with possibilities, and with this handy book, you can explore them all.