Battery Life

With the move from featurephones to smartphones, battery life has been and continues to be a critical issue. While it wasn’t unusual to see a week or more of battery life on a featurephone, some of the earliest smartphones couldn’t even last a day. While tablets seem to have a much easier time achieving high levels of battery life by virtue of massively increased volume, they still face similar issues as they are often used for gaming or other more intensive workloads that a smartphone is unlikely to see nearly as often. In order to test this, we run our tablets through a standard suite of tests of various use cases. In all cases where the display is on, all displays are calibrated to a brightness of 200 nits to draw useful relative comparisons.

Web Browsing Battery Life (WiFi)

In our first test, we see that the iPad Air 2 is about roughly equivalent to the original iPad Air for WiFi web browsing. This is actually a bit surprising as the battery in the iPad Air 2 is approximately 84% of the iPad Air. This would mean that we would expect the iPad Air 2 to get around 8.4 hours of battery life in this test, which represents a 16% gain to efficiency. It’s likely that these improvements to battery life come from the new process node on the A8X, along with the newer WiFi module.

Web Browsing Battery Life (4G LTE)

Along the same lines, the LTE web browsing test tracks quite closely but it seems that there’s a minor decrease in efficiency gains when compared to WiFi. This difference is likely to be explained by the much higher bandwidth available in WiFi when compared to LTE.

While the web browsing tests are effective at ensuring faster SoCs aren’t punished, this inherently tilts battery life towards a more display-bound mode rather than compute-bound. Unfortunately short of a jailbreak it doesn’t seem possible to get an effective Basemark OS II battery test, so we’re mostly limited to a test of GFXBench’s unlimited rundown.

GFXBench 3.0 Battery Life

GFXBench 3.0 Performance Degradation

As one can see, the iPad Air 2 is one of the best performers on this test, considering its frame rate and runtime. While NVIDIA's GK20A GPU in Tegra K1 can get close to the GX6650 for short periods of time, over a long workload it's pretty clear that the GX6650 on 20nm has better sustained performance and significantly superior efficiency as it doesn't throttle until the 200th iteration of the test. It's important to note that the iPad Air 2 is running at a higher native resolution here, so relative to SHIELD Tablet a scaling factor needs to be estimated in order to get an idea for performance at the same resolution. During this test I saw that the skin temperatures never exceeded 45C, so this isn't the result of Apple choosing to run the device hotter than most.

Charge Time

While tablets deliver some great battery life in general, charge time tends to be much slower than that of smartphones as the battery is much larger and charging the device isn't as time critical due to the longer battery life . While we can't quite cover the full range of battery life uses cases, it's important to remember that in cases where the platform is otherwise identical beyond display that battery life scales linearly with overall capacity. In order to test charge time, we measure the time it takes for the battery to reach 100% from a fully-depleted state.

Charge Time

As one can see, the smaller battery seems to have a noticeable impact on charge time, although the difference isn't really all that notable as the difference is only around ten minutes at the end of the day.

GPU and NAND Performance Software: iOS 8


View All Comments

  • IUU - Friday, November 7, 2014 - link

    Like what? Reply
  • lucastbosa - Saturday, November 8, 2014 - link

    Like Paper, by 53. Or iMovie, Garage Band, and many others. Reply
  • carloshehe - Sunday, November 9, 2014 - link

    Yes. Actually just the apps that come with iPad for free from Apple there's nothing like it on Android.

    Then you actually open the App Store and it is game over for Android.

    Like I said. Some games. Email, video, web browsing and light work you can do on an Android tablet, but for anything heavier forget it. The iPad is still the very best.
  • carloshehe - Sunday, November 9, 2014 - link

    Like iDraw (vector design program like illustrator)


    There are so many I could go on forever.

    Android tablet apps are exactly 0. It sucks for tablets.
  • NEDM64 - Sunday, November 9, 2014 - link

    My favorite latex editor: TexPad.

    Mendley, etc...
  • tralalalalalala40 - Thursday, November 13, 2014 - link

    Check out pythonista, grafio, and get console :) Reply
  • tralalalalalala40 - Friday, November 7, 2014 - link

    Android isn't perfect either. It's more closed source every day.

    In the tablet space, you have to be a hardcore fanboy to get the nexus 9. There is an order of magnitude more apps custom built for the iPad.

    But if you just want a portable TV, get android tablets, they are much cheaper.
  • Guspaz - Friday, November 7, 2014 - link

    Considering the Nexus 9's reviews (pretty much every review I've seen is negative), you'd probably be better off with a tablet from Samsung or something. Reply
  • steven75 - Friday, November 7, 2014 - link

    The Nexus 9 could be a third of the price of the iPad and I'd still pick it because:
    -My data isn't being mined by the world's largest advertising company
    -iPad app ecosystem is *still* >>>>>>> Android tablet ecosystem
    -Resale value through the roof
    -After sale support in person. Imagine that!
  • steven75 - Friday, November 7, 2014 - link

    Pick the ipad, obviously. Reply

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