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

  • george1924 - Saturday, March 19, 2011 - link

    Seems to be fixed now Reply
  • Anand Lal Shimpi - Saturday, March 19, 2011 - link

    Thanks for the correction :)

    Take care,
    Anand
    Reply
  • drugos - Saturday, March 19, 2011 - link

    As usual, one of the most comprehensive reviews on the net. Thanks guys! Reply
  • Bosh - Sunday, March 20, 2011 - link

    Yes, as usual ! Reply
  • PrinceGaz - Saturday, March 19, 2011 - link

    Who buys worthless over-priced rubbish like the iPad, apart from hipsters/dickheads? I can understand the appeal of it to them, and I've nothing against dickheads who love them, but what purpose do they serve to the rest of us?!?

    It's incapable of being used for real work so basically useless except as a toy when out and about, but too large to be carried around in anything smaller than what a small laptop could be carried in, so what it can do when on the move may as well be done on a smartphone.
    Reply
  • B3an - Saturday, March 19, 2011 - link

    Cant beleive i'm saying this about an Apple product... but the iPad 2 isn't expensive for the hardware. Look at the Motorola Xoom which is lot more expensive for marginally better hardware, although the iPad 2 has better hardware in some areas. The thing is though Apple can sell the iPad 2 at little profit because they just make the money from app sales. So it's hard for other tablet makers to compete on price.

    I agree with everything else though.
    Reply
  • shabby - Saturday, March 19, 2011 - link

    The ipad2 is expensive, imagine if asus took their $250 10" netbook and removed the keyboard, replaced the hard drive with a sd card for memory, and ditched the intel mobo/cpu for a slower soc this thing would cost maybe $150.
    The only reason these devices have these prices is because that's how much people are willing to pay for them.

    As for the xoom, motorola for some reason thinks they can charge a premium for it, they certainly are smoking some good shit. These phone manufacturers will fail with their expensive tablets.

    Once asus and other netbook manufacturers start saturating the market with android tablets you'll start seeing cheaper solutions.
    Reply
  • jalexoid - Saturday, March 19, 2011 - link

    That is not true. FOB price for the 16GB XOOM clone(proper quality clone, not a knockoff) is about $330. Smaller components cost more. Reply
  • WaltFrench - Sunday, March 20, 2011 - link

    “The only reason these devices have these prices is because that's how much people are willing to pay for them.”

    Showing off the fact that we've had Econ 101, are we?

    Perhaps there's some object/service that operates differently that you'd care to mention.
    Reply
  • kukabuka - Saturday, March 19, 2011 - link

    Well, I for one think tablets are really great when you don't need a keyboard or a fast processor or a lot of storage. Which would be never. If the iPad sells way better than the Xoom, I'd say your theory about hipsters/dickheads being the only market group for tablets is confirmed. Reply

Log in

Don't have an account? Sign up now