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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  • vol7ron - Sunday, March 20, 2011 - link

    Smoking the magic of realism, that's the point this device needs to hit. You can take that back to your IPS gods.

    I didn't say it was feasible to happen right away, but that's where it needs to be for the low-end devices. The upper-end of the spectrum should land in around $450.

    BTW, you misunderstand R&D and cost procurement. Just because these devices have a hefty starting price does not mean the cost of materials is even 1/1000 of that price. Whether the service providers are eating the price, or not, it all comes down to the fact that these devices do have a large mark-up. I think you need to consider the cost of an iPod Touch to the iPhone if you need a simpler way to compare - the 3G modem doesn't cost $300 lol and the Touch still had a high mark-up.

    "when the competition with a 2 decade head start still hasn’t been able to compete on price" ... no one has had a 2-decade head start. Technology (manufacturing and supply chain) and costs have both shifted over the last 20 years to make things more affordable. You come at this with an emotional response of "that can't happen", when I say it can and it will. Be care about being shortsighted it will come back to bite you one way or another.
    Reply
  • name99 - Sunday, March 20, 2011 - link

    Look, if you want a crappy cheap computer, go out and buy one. They make $50 computers (none of that extravagant $100 OLPC nonsense) for India powered by 6502s.

    But at the end of the day you are being disingenuous. You don't ACTUALLY want a $250 PC --- you can get something like that today if you buy a second hand Eee on eBay. What you want is an actual iPad, not something with a tenth of the functionality, but at $250.
    Good luck with that.

    And spare us this "eventually". If you're not content with a $250 eBay Eee now, buy the time the $250 iPad equivalent comes around, the real iPad 5 will be quadcore, 2GiB of RAM and a retina display screen, and you STILL won't find the cheap equivalent an acceptable choice, not when there's a real device at $600 that is so much better.
    Reply
  • medi01 - Monday, March 21, 2011 - link

    "Competition" has such devices for as low as about 100$, go google. They don't come with IPS panel or good battery, but how much do those parts cost?

    Competitors like Samsung do not have any reason to lower prices, as they are competing for different customers anyway. Not to mention, people perceive cheaper devices to be inferior.
    Reply
  • medi01 - Monday, March 21, 2011 - link

    PS
    There are NETBOOKS (from Acer, Lenovo or pretty much anyone) with multi-touch screens for below 300$.
    Reply
  • michael2k - Monday, March 21, 2011 - link

    They also weigh 2 to 3 times as much and have half or less the battery life. Reply
  • sean.crees - Monday, March 21, 2011 - link

    I still am amazed when people complain about the iPad being too expensive. I remember a little over a year ago everyone expected it to have a starting price of $999. It debuted at half that, and people still complain it's too much.

    It's now a year later, and even Apple's competitors cannot make a device that is competitive with a $499 starting price point or less.

    Here is where i see the iPad fitting in. The console and notebook have effectively replaced my PC. Everything i used to do on a PC i now do on either my notebook or my PS3. You're always going to have a cellphone. The tablet then does what you used to use a notebook for 10 years ago.

    You end up with a cell phone, a tablet, a notebook and if you want to game, a console.

    I don't know if a tablet will ever replace a notebook, maybe for some who can't afford all 3 and have to choose between a tablet and a notebook and don't need the productivity and power you gain with a notebook. Like how a TV is just for media consumption, a tablet is the same but you carry it around with you.
    Reply
  • Mishera - Tuesday, March 22, 2011 - link

    People complain about the device being too expensive because for what it is capable of doing, and compared to other devices it is overpriced. For Apple the price makes perfect sense for what they portray as a luxury device. It starts with enough room to drop the price (which they did sort of) and to be able to introduce another smaller ipad at some point in the future without cutting into their sails of macs. That's probably why they went with their keyboard choice.

    I thought about buying one but came to the conclusion that it simply was far to expensive to justify, especially since all I needed was an ereader, and later a new laptop. But I ended up getting on for Christmas so I wasn't complaining. Turns out the iPad is for EXACTLY what Steve said it was for. This is essentially a couch companion. This takes care of all my computer need when I'm at home and don't have to do work. But that's about all it's good for since it's too big to feasible carry around and doesn't replace your laptop.

    I still stand by my belief that the ipad is overpriced though much more attractive at $400. I think tablets will be very important in the future, it's just that they are far away and apple right now is only interested in making consumer devices while everyone else follows them. But right now everyone seems happy with just a new toy..
    Reply
  • george1924 - Saturday, March 19, 2011 - link

    DSC_2328.jpg and DSC_2364.jpg Reply
  • george1924 - Saturday, March 19, 2011 - link

    Great in-depth review though! Still can't get excited about tablets very much yet. I've had fun playing around with them, but don't think I could justify it along with a laptop, desktop, etc... Reply
  • MonkeyPaw - Saturday, March 19, 2011 - link

    Yeah, and the problem with playing with them at the store is that they always look really gross. I was messing with a tablet at a store today, and immediately washed my hands afterwards. I'm not a huge germ-a-phobe, but when I guy blows his nose, then approaches the electronics, I just start getting uneasy. I guess the screen just shows what's on all the mice and keyboards there, too. :p Reply

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