First Macbook.. a little confused

Discussion in 'MacBook Air' started by johnz, Jul 11, 2013.

  1. johnz macrumors newbie

    Feb 23, 2013
    Hi guys I bought a 13" 2013 model with an i7/8gb/256ssd. It came in this Monday.

    So far I am happy with my first Apple product but I acquired iStat and have been watching Apple's own built in battery life estimates as well. Looking at my battery, it says I have 6 cycles so far with a design capacity of 7150mah but a current capacity of 7382mah. That makes me a little confused as to how it is higher.

    I read around and saw people saying that it takes a few cycles for the battery to reach its full potential. Is that true?

    To clarify, I don't do much so far. Skype running, ~3 Chrome Tabs (testing from Safari -> Firefox -> now trying and typing this on Chrome) while having Steam open. Is this normal? Brightness is always ~50% with keyboard backlight off. No bluetooth or time capsule, and I don't believe my Spotlight is indexing which I have heard to be a killer.

    Thank you guys.
  2. Dalton63841 macrumors 65816


    Nov 27, 2010
    This is precisely why I don't use apps like iStat. They don't actually infer much USEFUL data. The data it outputs varies based on what you are currently doing, the method you charge your battery, the time of day, and whether the wind is blowing out of the west.

    The battery does take a few cycles to reach its peak, all those numbers you are seeing are perfectly normal.

    As far as the max capacity, think about it this way... A batch of batteries are made in a factory... The likelihood of every battery having an identical capacity is statistically impossible, so they give themselves a window, i.e. a tiny bit under or over is okay. The battery gets put in the laptop and sent to you with a design capacity of 7150mAh, but a REAL capacity of slightly over. Lucky you. Still, that number is likely to change after the battery is calibrated(which you should do).
  3. falconeight Guest


    Apr 6, 2010
    All my macs always came with charge cycles and had more capacity than it was supposed to have. Regardless of what app I used to test it.
  4. jasonbrent macrumors newbie

    Jul 28, 2007
    In a terminal, run the command

    ioreg -r -n AppleSmartBattery
    .. this provides the battery information that MacOS has available to it. One of the outputs there is

          "MaxCapacity" = 7258
    That's where the high reading is coming from in iStat menus. .. It seems that this is actually a calculated value (probably measured based on resistance during charging/etc) as it will vary some as the battery charges up/down.

    What apple is effectively guaranteeing you is a minimum of

          "DesignCapacity" = 7150
    mAh in the battery "stock".

    ... in fact, as I've typed this, my battery readings have changed again... (this output is from an app I'm writing, but uses the same underlying datasource in Mac OS)

    Thu Jul 11 22:32:22 2013 -> currently draining at -1065 mAh [6780 of 7150 max: 7250]
    So nothing to worry about. Complete normal...

  5. johnz thread starter macrumors newbie

    Feb 23, 2013
    Thank you very much for the help guys. It definitely gives me some piece of mind. Battery life is very good none the less, nothing to really complain about considering what has existed for so long already. I can't complain. Hopefully after some more charge cycles things level out to be even better! Thanks again. :)

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