Battery Life And Recharge Time
Battery Life & Recharge Benchmarks (Background Info)
The second-generation Kindle Fire and Fire HD are middle-of-the-road performers in our movie playback test, delivering about six hours of battery life.
Notably, the MIMO Wi-Fi antenna configuration seems to be a major benefit in the browsing test, where the Kindle Fire HD overcomes the deficit seen above to enable more than seven hours of use. That's enough to almost match the Nexus 7.
Normalized Brightness Benchmarks
We know that a great number of users set their mobile devices to maximum brightness, which is why most of our battery data is taken in this real-world way. However, tablets don't share the same brightness ceiling, making such a comparison imprecise.
Although the battery life numbers below are captured at standardized settings to put each screen on even ground, it's common to dial up brightness on a low-gamut LCD to improve readability or visibility. Moreover, even if you put two devices calibrated for the same brightness side by side, there's no guarantee they'll look the same due to differences in screen quality. The only thing we're doing is fixing the luminance of a display for testing purposes.
Normalized to 200 cd/m2 (or nits), the Kindle Fire HD runs for nearly 10 hours while watching H.264-encoded video content. We don't have the first-gen Kindle Fire here to compare any more, but the second-generation model runs for seven and a half hours. But both tablets fall slightly behind Google's Nexus 7.
When it comes to Web browsing and music playback, the Kindle Fire HD jumps to the front of the pack, topping the third-gen iPad.
Gaming is becoming far more common on tablets. Unfortunately, it's difficult for us to find cross-platform benchmarks because there are so few games that run on both iOS and Android. Riptide GP is one of the few, and we put it on a demo loop to drain battery life. In some ways, this test is less forgiving to Tegra 3-based tablets because Riptide is specially optimized for Nvidia's SoC. As a result, we do see the Fire HD and second-gen Fire ahead of the Nexus 7, though behind the iPads.
Amazon no longer ships an AC charger with its tablets. So, our recharge benchmarks for the second-generation Kindle Fire and Fire HD are the result of using the Amazon's new PowerFast charger (opens in new tab), sold separately for $10.
With charging times to 90% under three hours and to 100% just over that, the second-gen Kindle Fire and Kindle Fire HD are ready to hit the road again in less time than either of our iPads and both of Samsung's Galaxy Tabs.