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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  • Mishera - Wednesday, March 23, 2011 - link

    An and you made an excellent point when you said that tablets don't seem on a path towards perfection.  Right now IPads are somewhat of a novelty.  They're kind of like that thing you see at a museum as a child that make you go "wow" or a concept at a convention that's not fully realized.  The problem is people seem content with the device as it is because it's Apple, and companies are trying the "square in circle" method to put it in schools, businesses, etc.

    Thats what really bothers me. Apple pretty much marches on it's own beat, consumers eat up what they release, and companies desperately try to run behind them and release something with better specs, never questioning if there is a better direction.  As a consumer device it's excellent, its just there are so many more directions tablets can go.  I would almost would say that Microsoft had a better idea of what a tablet should be with their umpc line, except they could never get the ui right, and now it seems like their hardware endeavors are over for so I wonder who could really bring a better concept to market.  To make tablets work it's going to take on os and a hardware so far android can't do it, microsoft won't to it and hp is still a question mark so we just have to be content with whatever apple gives us.  
    Reply
  • Zink - Sunday, March 27, 2011 - link

    Here's a very surprising video showing the flexibility of the glass used in the screen.
    http://www.youtube.com/watch?feature=player_embedd...
    Reply
  • JustinB - Monday, March 28, 2011 - link

    While OEMs are racing to create a competitor to the iPad, it seems like commenters on sites like this are trying to create a competitor to the Reality Distortion Field... Reply
  • NetJunky - Tuesday, April 19, 2011 - link

    Actually Dropbox has its own lack of security. So I wouldn't say, that this is a best example of data sharing via web. Reply
  • Bronx 6 - Tuesday, June 28, 2011 - link

    Apple had touch first congrats.They can keep there not so tech ridiculously rich ppl who buy lesser powerful or frivolous shoppers.xoom is to much with not enough (like ipad) on board no dongle needed ports/hdmi/usb/micro usb like acer.i bought an ipad2 as my first owned apple product just so I could show everyone whata piece crap it is and then return it to the store.The things I get off android apps are sooooooo much better because they arent being ran by the Nazi's (apple).,i like not having to waste money on anything app wise,movie(better than anything I could dream for) and of course free absolutely FREE music mp3s.now I even get artwork on them and they appear just as if I bought them.The music mp3 apps even (some) even include music charts so you know what's new and hot.i dont need cable tv,satelite,nadda I get thousands of channels free from apps which use flash and lemme tell flash is the key to the future and present.i love how developers make the good apps ipad has for honeycomb tabs(splashtop hd remote desktop)-myfav allows me to use all pcs as if I was on it even whem im in another state.the resolution is amazing also the many keyboards u can get-new swype is surreal should be stock on all tabs.tried to ruin acertab with viruses it wont phase it amazing alone.i so love the apps on droid they are made by ppl wno arent like the government and honeycomb keeps getting better asnow 3.1 is so muchbetter and its free.the power.of these tabs are like two ipads and the cameras on ipad2 is patheic like an old boostmobile vga cam.mine has the same quality cameras as iphone4 has another + acer has the best tab for the buck they have a functual full usb port and it connects alot.of useful things like keyboard,flashdrives,ch arging capabilites.i had bought one accessery a case stand that's it had hdmi cords already.the ipad I bought over 8 seperate things totally a money hungry company who designs product too keep you buying shit week after week.itunes is just plain retarded.i get the sameshit they do for free easier than a pc.wide open is free like usa is supposedly.if ur reading this and have a tablet download swype beta for honeycomb.It takes the basic stock keyboard but adds stuff u will love even if you dont swype u type better than the stock more like a real one.i bought 2apps in 2YRS yet ive had more than I can think of.i spent $8 total.i have sold more of these to anyone I show and teach.my old mother has one and now wont use her win7 pc's only thru the tablet-thats including me fixing her old pcs accross the country in california all from my badass acer tablet.apple should stick to ipods.droid tabs are diffently ipad.killers.i hope ppl enjoy wasting their money basically getting raped.so dumb ppl stay apple,smart ppl sick of paying for things that we shouldnt and having the ability to do all n then some on tablets enjoy.ps these flash modified apps on droids I cant praise the quality they look during playback is wow.ive watched more hdtv thru this than I have in years with my hdtv sets pretty crazy,so is the gaming similar to xbox360.buy an galaxy tab first then return it for an acer so you can appreciate getting more for less.send me the difference for enlighting u on values of better things.then again the world is more than 50% ignorant and very rude to ones who help them.take it as grain of salt Reply
  • rampantarmadillo - Thursday, August 18, 2011 - link

    I recommend that you learn to seperate vertex and fragment perf, this would demonstrate you aren't clowns. Reply
  • powchie - Saturday, December 10, 2011 - link

    anand, brian,
    what's that workflow that the iPad cannot fit in?
    Reply
  • ChaoticCupcake - Tuesday, December 27, 2011 - link

    Any word on whether or not a camera can be attached and used as a webcam for FaceTime, Skype, etc.? Reply
  • omkarphatak - Tuesday, February 28, 2012 - link

    Find out why choosing an iPad 2 over a laptop makes no sense... http://www.buzzle.com/articles/which-is-better-ipa... Reply

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