real world battery times - 11" or 13" - your experience?

Discussion in 'MacBook Air' started by sbb155, Feb 10, 2011.

  1. sbb155 macrumors 6502

    Jan 15, 2005
    How long does your MBA last, generally speaking, and under what conditions are you working?
    For example is it: 11", surfing, 4-6 hours
    13" - video, surfing, email - 5-5.5 hours

    etc etc etc

    I am considering the 13" after a bad experience with the 11" battery, but want to get objective numbers....
    Thanks guys,
  2. shamash macrumors 6502a


    Jul 19, 2008
    Taichung, Taiwan
    I just got my 13", but I was downloading a torrent with uTorrent, had iTunes playing, had 2 microsoft word documents open, finder and settings open, Atlantis (a mud client) open, Adium and Good Chrome to browse the web, and it was at 80% with 4.5-5.5 hours left. (it went up and down as i switched between things, but didn't go below 4.5)

    Its pretty sexy :D
  3. bri1232001 macrumors newbie

    Jan 4, 2011
    Just because your mac says x hours left at y% battery does not mean thats what you'll get.

    Is there an application that will track my time vs battery % and compare it to what the machine estimates. I'd like to know how long I'm actually getting from my battery per each lets say, 5% or 10% charge.
  4. axu539 macrumors 6502a

    Dec 31, 2010
    From my experience, if the battery is properly calibrated, that is usually pretty accurate.
  5. bri1232001 macrumors newbie

    Jan 4, 2011
    When it estimates 5 hours while I'm lightly surfing then yeah it likely is accurate. My usage is anything but constant though. I lightly surf, netflix for a bit (seems to really get my CPU going), open parallels briefly if I need to, then perhaps let the mac stay on while I read a homework problem and refer to an ebook on it.

    For me the estimation is constantly changing as I use the program. It is also an "estimate" for a reason.

    I guess I'm looking for a tracker or monitor, rather than an estimator.
  6. shamash macrumors 6502a


    Jul 19, 2008
    Taichung, Taiwan
    Agreed. Also want to point out that my battery seems to change due to temperature and other things. I was just outside with the MBA having Chrome, iTunes, Adium, Word, Atlantis and Textwrangler open. It was at 3 hours 30 minutes with 98%. I went back inside, it leaped to 4:38, then 5:02, and its still rising.
  7. bri1232001 macrumors newbie

    Jan 4, 2011
    So you agree that yours is pretty accurate yet state that it varies by an hour and a half just from the location you are using it in!

    Not in anyway the definition of accurate, that is unless the temp of the battery actually does have that drastic of an effect on its performance.
  8. axu539 macrumors 6502a

    Dec 31, 2010
    Actually, temperature probably does have some effect on the battery, since the battery does use a chemical reaction. However, in this case, it might just be that it's been so cold in many places that the sensors are being thrown off.
  9. notjustjay macrumors 603


    Sep 19, 2003
    Canada, eh?
    Temperature does indeed greatly affect battery performance.
  10. GGJstudios macrumors Westmere


    May 16, 2008
    Your battery indicator is a constantly-changing estimate, based on current power demands of your MBA. Calibrate your battery properly (instructions in the following link) to make sure the indicators are as accurate as possible.

    This should answer most, if not all, of your battery questions:
  11. tmoerel macrumors 6502

    Jan 24, 2008
    Temperature has an influence yes. Recently i used my 13" somewhere where it was -15 degrees celsius. Normally i can use my machine for about 6 hours with wifi engaged and brightness at 50%.
    With the cold it only lasted about 3 hours.
  12. Xeperu macrumors 6502

    May 3, 2010
    13" with 128GB SDD + 1.86 CPU = 7 hours of real world use. Light use, office + internet.

    Screen at 40%. Bluetooth off, wifi off. (Airplane)

    About 6 hours, same conditions but WiFi and Bluetooth on. With light browsing, sans Flash.
  13. Whorehay macrumors 6502a


    Feb 17, 2008
    11" 1.6/4/128.

    With pretty heavy Flash usage (for Google Finance charts), 50% brightness, bluetooth off, and with Microsoft Word/Powerpoint, Safari, and Adium running, we're looking at just about 5 hours, or about an hour per 19-21%. I would guess that heavier Safari usage would probably push it to 22-25% per hour of drainage.

    A little less than my previous netbook (Dell Mini 10v) which could get a legit 6 hours of battery life, but obviously the MBA much more powerful, capable and much thinner.
  14. impulse462 macrumors 68000


    Jun 3, 2009
    With moderate web-browsing, itunes, and light word processing with my screen brightness set to 25%, I received 6hrs and 31 minutes of battery life.

    I'm assuming with my screen brightness set at 50%, I'd receive around 6 hours with the same usage.
  15. neopickaze macrumors newbie

    Jan 18, 2011
    With Spotify on WiFi, chrome with a few tabs, coda and mail open I get about 6 hours real world usage on my 13", brightness 2 notches down from maximum.

    I know this is pretty accurate as I have the laptop on charge while I'm using it at work during my day job, then I do another 4 hours at the office (where I don't have a charger) and a couple of hours of iPlayer or other video streaming when I get home.

    Thinking about it I probably do get about 7 hours usage from a charge.

    I do use Coolbook with CPU undervolted to minimum but not underclocked so I think this has a hand, I'd probably get an hour less without it.
  16. bri1232001 macrumors newbie

    Jan 4, 2011
    So you see no performance loss yet better battery life by undervolting.
    If undervolting is so great why isn't it done by default?

    This leads me to believe there has to be some sort of consequence of undervolting.
  17. 2IS macrumors 68030

    Jan 9, 2011
    Becasue not all processors are created equal. Some processors will work perfectly fine at a lower voltage while other processors even of the same model won't. Intel isn't going to test every single CPU die that comes out of their fabs so they simply over-volt all of them so even the worst of the bunch are stable. If you happen to have one of the crappy ones, you probably won't be able to undervolt much before the chip becomes unstable. C2D's are very mature now so it's rare that this would happen.

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