The story of the Galaxy S II's battery life cannot be told without returning to its luscious screen. Being an OLED panel, the 4.3-inch display here doesn't use one single backlight as LCD screens do, and instead only illuminates the pixels that are needed to actively display content. This is the reason why it can generate truer blacks than any backlit panel, but it also permits the user to optimize battery life by doing such things as switching to a darker wallpaper or reading ebooks against a black background. We didn't actually bother with such tweaks, we were too busy exploring every one of the myriad features on this phone, but the option's there as an extra dimension of obsessive control if you care for it. As to the Galaxy S II's actual endurance, we found it highly competitive with the latest batch of Android phones. After 20 hours, half of which were filled with the above tinkering and exploration, we managed to drag the Galaxy S II down to 15 percent of its original charge. This was with our usual push notification suppliers, Gmail and Twitter, running in the background and while constantly connected to our WiFi network.
Using the Android System Info app (available for free on the Android Market), we found confirmation that the Galaxy S II is indeed running a 1.2GHz ARMv7 dual-core processor, but more importantly, we also dug up a breakdown of how often the SOC was reaching that max speed. Only 9.2 percent of our use harnessed the full 1.2GHz, with Samsung wisely downclocking its chip to as low as 200MHz when the phone's idling (that accounted for 46 percent of the Galaxy S II's uptime). What's impressive about this is that we never hit upon any performance bumps to indicate that we were running at slower speeds. Clearly, Samsung's power management system is doing its job well. In summary, we expect you'll be able to get a decent couple of days' regular use out of the Galaxy S II -- our experience with it mirrored what we got out of HTC's Incredible S and Desire S that recently crossed our review bench -- though processor-intensive activities like HD video playback will eat into that, as will the variability of 3G coverage. What we can say with absolute certainty is that the Galaxy S II is no slouch when put against its contemporaries, and it also marks a definite improvement in longevity over the original Galaxy S.