Slate's David Sessions was wondering exactly how Apple has- at least by their own tested explanations- lengthened the battery life of the iPhone to as much as eight hours.
Sessions then got busy, talking to some experts about how this could be done.
Experts such as Richard Doherty of the Envisioneering Group, Rob Enderle of the Enderle Group, Ian Hill of the NRC Institute for Chemical Progress and Environmental Technology, and Brian Lam of Gizmodo.
Here's David's distillation of what he was told:
One way to improve power efficiency is to upgrade the hardware. A smart phone's circuit board incorporates dozens of chips that control the display, operating system, and the phone's wireless connection, among other things. Along with the screen, chips are the biggest power-consumers in a cellular device. By working with numerous chip manufacturers, Apple and other electronics companies can pick and choose individual chips that are particularly energy efficient. The iPhone's glass screen, announced this week, will also help save energy. Glass transmits light more efficiently than plastic, which will allow the iPhone's screen to maintain the same brightness while using a little less power.
Another way to extend battery life is to shut down parts that aren't in use. The more tasks a phone is running (phone calls, Web browsing sessions) the more quickly the battery gets depleted. Advanced operating systems—iPhone uses a version of Apple's OS X—can regulate the device's power usage, powering down the processor or the screen when they're not active. (Tech companies occasionally calculate a device's battery life with most of its hardware components shut off, an unrealistic situation that tends to produce an inflated projection of the gadget's real-world power consumption. Apple claims it tested iPhone's talk time with all of its default features turned on except the Wi-Fi network scanner.
I still think eight hours will be more the exception than the rule.