iPhone 4S battery life

Q: I’m confused by the battery life on the iPhone 4S. I thought Apple had said that it has a better battery, yet the specs say that it gets a lot less standby time. However, it also has better talk time. How can the battery be better for talking yet worse when it’s just sitting there?

– Anonymous

A: There is a lot more to battery performance in modern electronic devices than simply the size or capacity of the battery. The chips and components all consume varying amounts of power depending on what you’re doing with the device, and improving battery performance is often as much—if not more—about making these components more efficient than simply shoving in the biggest battery possible.

For cellular communication devices, one of the most significant sources of battery drain generally comes from the radio equipment—the components that communicate with the cellular network, sending and receiving voice and data for calls, web browsing and so forth. This is why talk time is normally measured in hours while standby time is measured in days.

We don’t yet have any information on whether the battery itself has actually been improved in the iPhone 4S or whether the benefits come from the new wireless chipset and antenna system, but the fact that 3G talk time is the only number that’s improved suggests the latter. Most other battery performance numbers remain the same, with Wi-Fi Internet Use actually having gone down by one hour—from 10 hours on the iPhone 4 to 9 hours on the iPhone 4S.

The iPhone 4S does bring with it a much faster, dual-core A5 processor.

Apple claims that the A5 has the “same low power consumption” as the A4, but that doesn’t mean that the power consumption is completely identical under all conditions. The A5 may consume about the same peak power as the A4 did, but may consume more power when running in a more idle state. Other components such as the Wi-Fi and Bluetooth chipset and additional RAM can also account for power consumption differences.

Note that it is not clear how Apple measures standby battery life, but this is also not something the average user needs to be directly concerned about. Even 200 hours of standby battery life equates to just over 8 days and it’s relatively rare for any iPhone that’s being used normally to last more than one or two days on a single charge.