Battery qts. for new MBP

Discussion in 'MacBook Pro' started by Killerbob, Jul 17, 2010.

  1. Killerbob macrumors 6502a

    Joined:
    Jan 25, 2008
    #1
    Hi,

    I just got my new MBP; one of the i7s, and am especially happy with the better battery than in my old MBP.

    I see on Apple´s information, is a; built-in 77.5-watt-hour lithium-polymer battery. However, checking System Profiler, and Battery Health Monitor, the battery is "only" 6900 mAh :confused:

    KB
     
  2. RedReplicant macrumors 6502a

    Joined:
    Mar 31, 2010
  3. Kahalu'u Bob macrumors 6502a

    Kahalu'u Bob

    Joined:
    Aug 9, 2007
    Location:
    Honolulu
    #3
    Aloha Killer Bob. From one Bob to another: relax about the battery. It is fine. Do a search on this forum; there are probably more threads about batteries than almost anything else (except, perhaps, "yellow screens").

    Just use it for a couple of weeks, calibrate per Apple's instructions, and then see where you are. It is probably just fine. If your concern is mAh, load coconutBattery and see how it looks (don't expect perfection anything around 97% is fine). In my experience, personal and reading the forums, actual defective batteries are quite rare, and usually show up in about 12 - 18 months, not the first week of use. If others have noticed something else, I'm sure they will chime in here.

    But try the search function and read all the other threads about batteries. It may make you feel better.

    Cheers!
    Kahalu'u Bob
     
  4. Killerbob thread starter macrumors 6502a

    Joined:
    Jan 25, 2008
    #4
    Hi,

    Thanks for your very fast replies!

    What I mean is, if Apple is advertising a 77.5 mAh, and all checks tell me it is a 69 mAh battery installed, what´s going on?

    KB
     
  5. RedReplicant macrumors 6502a

    Joined:
    Mar 31, 2010
    #5
    77.5 Wh (watt hours) does not equal 77.5 mAh (milliamp hours)
     
  6. Killerbob thread starter macrumors 6502a

    Joined:
    Jan 25, 2008
    #6
    ahhhhhh

    My mistake. Is there a correlation at least?

    KB
     
  7. thebrick macrumors regular

    thebrick

    Joined:
    Apr 18, 2010
    Location:
    GA, United States
    #7
    mine shows like this...

    Current Cap is still slowly growing w/ each charging, Obviously lol
     

    Attached Files:

  8. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #8
    Nominal voltage 3.6 V per cell for normal Li-ion, I think there are 3 cells in series in a Mac, making 3.6 x 3 = 10.8 V nominal. Multiply the mAhr figure by this to get the power capacity in W hr

    6900 mA hr = 6.9 A hr
    6.9 A hr x 10.8 V = 74.5 W hr, close to what Apple specifies.

    Apple's Li-poly battery chemistry might be a tiny bit different to explain the difference, or it might just be some Steve Jobs RDF. Or my math might be wrong

    This site is worth a look
    http://www.batteryuniversity.com/partone-5A.htm

    It will tell you not to worry about your battery. My favourite quote is here
    http://www.batteryuniversity.com/partone-21.htm
    "No maintenance needed. Loses capacity due to aging whether used or not."
    ie don't worry about it, it will wear out, or not, regardless of what you do.

    Don't sweat the 6900 or 7086 mAhr number or whatever, it's just a wild guess by your Mac. Your Mac doesn't really know how much juice is in your battery. The only way to find out for sure is to run it down to dead empty - ie calibrate it - and see how much juice comes out. But next time the answer will be different:- temperature, age etc will all affect the answer quite a bit (maybe as much as 10%).

    I wouldn't even bother calibrating it unless you really want to. Calibration doesn't make the battery any "bigger" or "better", it just makes the on screen display (hours remaining) more accurate. And calibration involves running the battery to completely empty which is not particularly good for it.
     
  9. Killerbob thread starter macrumors 6502a

    Joined:
    Jan 25, 2008
    #9
    That´s why I love this forum. Ask, and someone will answer:D
     
  10. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #10
    And occasionally, the answer will be correct ;)
    enjoy your Mac
     

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