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
POST A COMMENT

189 Comments

View All Comments

  • FrederickL - Saturday, March 19, 2011 - link


    I have to say that I largely agree even though I perhaps would not use PrinceGaz' somewhat "undiplomatic" description of the iPad's current customer profile! However, I am obliged to agree that tablets of this size are of little interest (IMO) until they are functional enough that they can _replace_ ones laptop. The case for buying an iPad (fine piece of content consumption kit as it is) falls down at that first fence as far as I am concerned. In general terms my mobile device needs are met by my Desire Z. A third or fourth generation10 - 11 inch tab with a full slide out qwerty (either Honeycomb or Win 8 ARM, the iOS is not to my taste) with more connection/plug options than you can shake stick at, with a docking station+large screen at home - now THAT would open my wallet!
    Reply
  • dhuhtala - Sunday, March 20, 2011 - link

    I tend to agree - I've always carried a Blackberry phone instead of an iPhone just because it has a slide-out keyboard...I will not compromise on that! This makes the device really practical and I use it a lot.

    That's why I'm closely watching the ASUS eee Slider - a tablet with a slide out keyboard - that sounds like it will be much cheaper than the Xoom (rumour has it at $500.

    The Tegra 2 probably won't meet my requirements for playing MKV video files though, from what I've gathered...

    http://www.reghardware.com/2011/03/15/preview_tabl...
    Reply
  • solipsism - Sunday, March 20, 2011 - link

    You’re the minority. The majority of buyers just want something that works, which is why the techtarded people of the world are jumping into simpler devices for email and browsing, not building their own PCs and running a home-brew version of Linux. Reply
  • synaesthetic - Sunday, March 20, 2011 - link

    A netbook can check email and browse the internet for significantly less money. Most people I know, even the techtarded as you so colorfully put it, realize this and do not buy an iPad.

    The people I know who buy iPads are college students who get Mommy and Daddy to pay for it, and hipsters.
    Reply
  • doobydoo - Sunday, March 20, 2011 - link

    I couldn't disagree more.

    I would say that technically savvy people are the ones who are MORE likely to buy an iPad.

    I say this as a technically savvy person who has not yet bought an iPad, but can see the appeal:

    Firstly - the iPad is lighter, thinner, and has better battery life than most netbooks.

    Secondly - it's more capable, in that u wont have to wait around for Windows or whatever OS you're using to load, the apps are designed for the platform and the device's capabilities so it's actually quicker. Games, for example, are much nicer to play and to control on an iPad when compared to a netbook.

    Thirdly - it's more convenient in certain situations - u dont need to find a table to set it on or put it on ur lap - you can just hold it, such as when standing up or walking along, or where ur sitting at a table with food all over it.

    Fourthly - it's touch screen, extremely advantageous in certain situations. For example, the iPad makes a much better presentation device than any netbook can.

    It's such blind ignorance of a lot of people on here to assume that it's non-techy people who buy iPads. It's the non-haters, who buy iPads. The people who want to embrace the latest technology and actually see what it's about before dismissing it with some pathetic stereotype.
    Reply
  • medi01 - Tuesday, March 22, 2011 - link

    It's a "for fun" device, so if you buy it for some thing else, I doubt your "tech savyiness".

    And for some, not being able to read stuff you've written to your own device, is a show-stopper. Calling this "hate" is silly.
    Reply
  • synaesthetic - Sunday, March 20, 2011 - link

    It pretty much is a toy, but I really think smartphones are better toys. They're smaller, and you carry your phone anyway, so why not game on it to kill some time between appointments? Reply
  • Rick83 - Saturday, March 19, 2011 - link

    I still stick to my 5" tablet (though something slightly larger might work also...but 7" is already too much).
    That I can carry around all day (when I want to, and keep a separate non-smart phone that does telephone well enough) and yet it is much more useful than the 4" and 3.5" smart phones. I can comfortably hold it with one hand, buttons are nice and big in landscape mode, the dock gives me USB host, there's BT for keyboards as well, dock with hdmi-out, analog video-out...basically it does anything I would ever need, in the ideal portable form factor.

    It could do with a marginally better touch screen and build quality, and performance and stability aren't that great, but considering it predated the first iPad by about 6 months, I'm willing to accept the odd quirk. Also, it still works after quite some use over the last 18 months, with no visible battery life issues.

    I hope that the mini-tablet form factor will be explored some more in the future, I would be willing to replace my current device with something similar once the warranty has expired...

    Oh did I mention that it cost me less than a third of an iPad? (But, no, no flash either ;))
    Reply
  • tzhu07 - Saturday, March 19, 2011 - link

    I've been trying to figure out a use for the iPad, and the only thing I can think of is that it's good for doing really simple things and taking notes. Also, when you take it out in front of a client during a lunch meeting, it tends to impress them.

    But, yeah, I find that there isn't really a need for a device that bridges the gap between a laptop and a smartphone....yet.
    Reply
  • vision33r - Saturday, March 19, 2011 - link

    It's all about the Apps, regardless which OS they are useless without apps.

    The iPad has tons of productivity and enterprise ready apps. Would like to see an iMovie clone on Android or some quality productivity apps. So far only iOS has the most real apps.
    Reply

Log in

Don't have an account? Sign up now