Testing battery life is quite time-consuming when you're looking at run times in the 10-hour range, so we only have numbers for the three Transformers. We had hoped to include results for the iPad 3, but we had fewer than three business days to prepare this review. There just wasn't enough time. The fact that the new iPad's battery takes forever to recharge didn't help, and neither did the fact that we fully cycle tablet batteries at least once before testing run times.
All testing was conducted in the balanced performance mode and at similar screen brightness settings. The original Transformer, the Transformer Prime, and the Transformer Pad 300 were all configured with a ~40% brightness level. The Infinity's screen is a tad darker, so it took a brightness setting of closer to 50% to get a good match.
First, we'll tackle web surfing using the default browser. Our browser test loads up a version of the TR home page and refreshes it every 45 seconds. New ads are loaded each time, and browser plugins are set to "on demand" to prevent Flash from burning through the battery.
The Transformer Pad Infinity lasted for just under nine hours in our web surfing test. Adding the dock extended the device's run time by six hours, giving the Infinity a definitive edge over the Transformer Prime.
Our second battery life test repeats an hour-long 480p video clip encoded with H.264. We use the ad-supported DicePlayer app, which supports the video decoding mojo in the Tegra 2 and 3 SoCs. This test is run in airplane mode, with Wi-Fi disabled.
The Transformer Pad Infinity looped our test video for more than nine hours on its own. Adding the keyboard dock extended the run time by nearly six hours, putting the Infinity neck-and-neck with the Prime but more than an hour behind the 300. Still, that's a good result for a high-PPI tablet. Remember that Apple had to make the iPad 3 thicker to accommodate the bigger battery required by the Retina panel. The Infinity's 1920x1200 display surely sucks more wattage than the other, low-res Transformers.