Battery Life

Testing battery life on a tablet is pretty grueling as these things are effectively smartphones with gigantic batteries. What would last for only a few hours on a smartphone can easily last over ten on a tablet. The iPad 2 is no exception.

As iFixit discovered, the iPad 2 features a nearly identical battery to the original iPad (25Wh vs. 24.8Wh). We already established that display brightness hasn't gone up so the only real impact on battery life will be because of the A5 SoC.


The iPad 2 WiFi's battery, courtesy iFixit

The ARM Cortex A9 tends to be more power efficient than its predecessor, the A8. With a shallower pipeline and the ability to execute instructions out of program order you get better performance per watt in most cases. As a result the A5 should complete bursts of instructions quicker than the A4 and get back to sleep sooner.

To put this to the test we put together a battery life test that combined our non-Flash smartphone web browsing test, checking for email every 15 minutes (via a Gmail account receiving ~100 emails per day) and constant local music playback while all of this is going on. The results are pretty much as expected:

General Usage - Web Browsing, Email & Music Playback

Over WiFi the Motorola Xoom and iPad 1 deliver very similar results. The iPad 2 pulls ahead by around 8%, it's not a huge advantage but it's there. Over 3G there's a noticeable drop in battery life, putting both of the iPad 2s below 10 hours and kicking the Xoom down to under 9 hours. All of the numbers on this chart are respectable however and you can expect a good day's worth of use out of any of these tablets.

Note that while the iPad 2 did better than its predecessor if you were to run an app that pegged both CPU cores at 100% you'd see reduced battery life on the iPad 2 vs. the iPad 1. Granted you'd also see better performance on the iPad 2.

Video playback is obviously an important function of these new tablets so we put together a H.264 decode playback test as well. For this test we transcoded a copy of Quantum of Solace from a 1080p BD source down to a 720p H.264 using Handbrake's Normal encode profile with one modification. In order to enable smooth playback on the Motorola Xoom we had to disable b-frames in the encode. The results are below:

Video Playback - H.264 720p Main Profile (No B-Frames)

The iPad 2 consistently lasted longer than the original iPad in our video playback test. The Xoom however did noticeably worse. Unfortunately only a portion of the H.264 decode pipeline is accelerated by NVIDIA's Tegra 2 in this test. When playing back anything more strenuous, portions of the pipeline are handled by the CPU cores in software. If you were to enable b-frames the Xoom would not only stutter but its battery life would drop to around 6 hours.

On the iPad 2 its Cortex A9s are mostly powered down during this test, on the Xoom the A9s are helping with the heavy lifting for video decode and as a result we see lower battery life. Kal-El is expected to address this issue head on.

The GPU: Apple's Gift to Game Developers HDMI Mirroring & Charging
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  • claytontullos - Saturday, March 19, 2011 - link

    http://technabob.com/blog/2011/03/18/ipad-2-refrig... kind of fun? Reply
  • vol7ron - Saturday, March 19, 2011 - link

    This just goes back to what I've said since the iPad was introduced. It'll be the +1 device that's best for laying around your house. This goes into my review as why it needs to hit the $200-250 price point.

    Sure it's a nice e-Reader and can entertain with some games and even allow for some production work, but it is still clunky and uncomfortable and to be efficient and productive you need the additional hardware, which are going to bring you in a nice laptop range anyhow.

    The 3GS is hitting the $50-100 price point w/ a 2 year contract, which I suggested a year ago. Personally, I still think that should be the price w/o the contract (to be available after-market for gifts/presents), but as long it's available at that point, that's where it needs to be.

    I still think the iPad needs to drop to that $200-250 point. It's the coffee table device, which people should consider having 2-3 spread-out in the home [ maybe one in the bathroom ;) ] - if only they could also self-sync wirelessly. I'm not too sure who buys the base model, but the specs alone would keep me from considering it and when you look at the higher spec'd models, it's not as justified when looking at laptops, or other eReaders.
    Reply
  • solipsism - Sunday, March 20, 2011 - link

    $200 to $250 for a newly released 10” Tablet with an IPS panel? WTF are you smoking? How can you have such an odd mental disconnect between writing that and then writing "The 3GS is hitting the $50-100 price point w/ a 2 year contract”? What part of 2-year contract aren’t you understanding? Do you not realize the carrier is paying Apple more than $200-250 for that 3GS, and you are paying the carrier a lot more than that over 2 years?

    Pray tell, how would this device be $200-250 when the competition with a 2 decade head start still hasn’t been able to compete on price?
    Reply
  • synaesthetic - Sunday, March 20, 2011 - link

    I don't get how they sell so many when they're so useless and clunky... and cost so much.

    Lot of hipsters I guess.
    Reply
  • michael2k - Sunday, March 20, 2011 - link

    The weight, battery life, and cost (altogether) are unparalleled in the computing world.

    Smartphones with similar performance characteristics have far smaller screens and lower battery life.

    PCs with similar battery life cost far more and weigh far more.

    PCs with similar weight (and still double at that) cost far more and have only fraction of the battery life.

    PCs with similar cost weigh far more and have drastically lower battery life.
    Reply
  • Meaker10 - Sunday, March 20, 2011 - link

    A dual core sandy bridge 13" device is going to be far more useful for work and far more powerful. Reply
  • michael2k - Sunday, March 20, 2011 - link

    Who said anything about work? For things like reading Anandtech it would be far heavier, bulkier, and with less battery life. Reply
  • bigboxes - Sunday, March 20, 2011 - link

    Just admit that it's a toy. The authors laid it out for you on how they prefer to use other devices instead of the iPad. It too bulky for portability and underpowered for any productivity tasks.

    So, you're telling me (and everyone else here) that you paid $500+ just to surf AnandTech on your couch? Just wondering.
    Reply
  • Stas - Monday, March 21, 2011 - link

    That's exactly why it cannot cost this much to be a reasonable buy. No, the following purchases are not reasonable: fa- sheep base, soccer moms that buy the latest gadget with most hype for their kids/husbands not even knowing wtf it does, or PR boost in form of including, again, the most hyped device with cars, hotel rooms, air travel, etc (3 categories right there probably account for 90% of all sales). I mean people that understand exactly what the device is, what it's not, and have a clear idea of how they are going to use it. And it doesn't matter how much it costs to make it, how advanced the hardware is, or how "revolutionary" the design is. Given the limited usability of a slim, touchscreen device, I think asking $600+ for one is ballsy. Reply
  • MScrip - Monday, March 21, 2011 - link

    -- "Given the limited usability of a slim, touchscreen device, I think asking $600+ for one is ballsy." --

    That's true about any tablet.

    As great as Honeycomb tablets are... they're still not gonna provide a true computing experience.

    A $600 laptop will always provide far more functionality than a $600 tablet...

    Yet... all these manufacturers are pumping out tablets at an alarming rate.

    Apple took the risk and added a new product to their lineup.

    If tablets were destined to fail... we wouldn't see Motorola, Samsung and even RIM jumping into the tablet game...
    Reply

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