iPhone: The Missing Manual

Battery-Life Tips

The biggest wolfers of electricity on your iPhone are its screen and its wireless features. Therefore, you can get substantially longer life from each battery charge by using these features:

• Dim the screen. In bright light, the screen brightens (but uses more battery power); in dim light, it darkens.

  The screen adjusts with the help of an ambient light sensor that's hiding behind the glass above the earpiece.

  You can use this information to your advantage. By covering up the sensor as you unlock the phone, you force it to a low-power, dim screen setting (because the phone believes that it's in a dark room). Or by holding it up to a light as you wake it, you get full brightness. In both cases, you've saved all the taps and navigation it would have taken you to find the manual brightness slider in Settings.

  Note

  Apple tried 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.

• Turn off the radios. The iPhone has three radios: one each for AT&T's cellular service, Wi-Fi Internet, and Bluetooth. You can turn off all three of them in one fell swoop by turning on Airplane mode (Turning Off the Antennas—and Airplane Mode). Do that whenever it's practical. You'll get a lot more life out of each charge.

  You can also leave the phone on and turn off Wi-Fi and Bluetooth as needed; ...