New MBA Battery Percentage Inaccurate

Discussion in 'MacBook Air' started by Mlrollin91, Aug 27, 2012.

  1. Mlrollin91 macrumors G4

    Mlrollin91

    Joined:
    Nov 20, 2008
    Location:
    Ventura County
    #1
    I just got a new 11" MBA but I've noticed something weird. Whenever I unplug it from the charger, the battery percentage in the menu bar is off by about 5%.

    The meter doesn't start draining until the battery itself is down to 95%.
    Same problem when charging it as well. The menu bar states that it is at 100% when it fact it is only at 95%. The charger turns green, but it continues to charge for another 30 minutes, until it truly is at 100%

    Oh, and what makes it even stranger, is when the battery gets down to about 50% its only 2-3% off, and closer to 10% its not off at all.. Its bizarre!

    I've done a SMC reset, repaired permissions and calibrated the battery.

    Anyone else experiencing something like this?
     
  2. KPOM macrumors G5

    Joined:
    Oct 23, 2010
    #2
    I've noticed this, as well, comparing results from iStat Pro or Coconut battery with the menu bar. This could be deliberate on Apple's part (to encourage people not to constantly charge the device), as the iPhone and iPad exhibit similar behavior (i.e. they stay at 100% for a long time).
     
  3. Mlrollin91 thread starter macrumors G4

    Mlrollin91

    Joined:
    Nov 20, 2008
    Location:
    Ventura County
    #3
    I'm glad I'm not the only one who has noticed this. I called apple this morning, they said that's really weird and set me up an appointment for the morning. They said it could be a deffective battery. It's just annoying that once the light turns green it needs an addition 30 minutes to charge to truly 100% not 95..
     
  4. pilotkid macrumors 6502a

    Joined:
    Aug 22, 2006
    Location:
    Chandler, AZ/Chicago, IL
    #4
    It happens on my 2012 11" also. It's annoying.
     
  5. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #5
    Battery readings are only estimates and are not 100% accurate. Also, it's a known issue that 3rd party battery apps differ from Mac OS X readings by roughly 5% in Mountain Lion.
    It's normal that your battery may stop charging between 93-99%. For details, read the CHARGING section of the following link.
    Repairing permissions has nothing to do with battery/power/charging issues. The built-in batteries in the newer Mac unibody notebooks come pre-calibrated and do not require regular calibration like the removable batteries in older Apple notebooks.
    Mac batteries are designed to charge quickly until near full charge, then charge slower until it's fully charged.

    This should answer most, if not all, of your battery/charging questions:
     
  6. Mlrollin91 thread starter macrumors G4

    Mlrollin91

    Joined:
    Nov 20, 2008
    Location:
    Ventura County
    #6
    I appreciate all the information. I just feel that its weird that my computer is telling me that it is at 100% even though it is actually at 95% according to the power section under about my mac. In addition, the light changes green on the MagSafe even though it is at 95% charged. I guess I am more concerned about ruining my battery if its being unplugged before it ever reaches a true full charge.
     
  7. Macman45, Aug 27, 2012
    Last edited: Aug 27, 2012

    Macman45 macrumors demi-god

    Macman45

    Joined:
    Jul 29, 2011
    Location:
    Somewhere Back In The Long Ago
    #7
    A 3% error either way is well documented, and the information in GGJ's posting should answer your questions...Remember that Apple warranty your battery if it falls off the cliff before a year has passed too.
     
  8. Mlrollin91 thread starter macrumors G4

    Mlrollin91

    Joined:
    Nov 20, 2008
    Location:
    Ventura County
    #8
    I read over the page, it has a lot of good information. I feel better about the whole situation now, even though it is annoying its definitely not the end of the world. I'm still going to swing by Apple in the morning for them to just check out the battery with their tools. Figure it doesn't hurt and its only down the street.

    Thanks to all that have responded, really appreciate the help.
     
  9. twintin macrumors 6502

    Joined:
    Aug 10, 2012
    Location:
    Sweden
    #9
    It works in exact same way on my Android phones as well (the green light kicks in roughly at 95%). Nothing wrong with this behaviour except it may look strange and some may find it irritating.
     
  10. macneubie macrumors regular

    Joined:
    Aug 8, 2011
    #10
    There's a free piece of battery app that can replace the coconut battery app here that gives more detailed info at the menu bar...
     

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