Why does battery health fluctuate?

Discussion in 'MacBook Pro' started by riptideMBP, Apr 18, 2012.

  1. riptideMBP macrumors 6502

    Joined:
    May 29, 2011
    #1
    So I found all the threads where people claim that battery health fluctuation is completely normal, but none of them seem to explain why this occurs. Can anyone explain the physical reasoning behind why battery health would go from 93% down to 88% and back up to 97% over the course of a few weeks?
     
  2. bobcan macrumors 6502a

    bobcan

    Joined:
    Jan 8, 2007
    Location:
    Sunny but Cold.. Canada
    #2
    Well, I am quite sure the 'internal measuring stick' is trying to gauge What you Do, When you Do It and For How Long.. it is accordingly extrapolating a bunch of DATA and then showing a somewhat arbitrary number..

    Although really not like a Fuel Economy Gauge (or Battery % Level) it is kinda similar I would think.. Overtime it just evens out.. and no matter what, USE your Computer and don't worry about it.. It will likely take more years off some people's lives than the battery itself!!

    :D
     
  3. DoNoHarm macrumors 65816

    DoNoHarm

    Joined:
    Oct 8, 2008
    Location:
    Maine
    #3
    Not to hijack the thread or anything, but my battery health doesn't seem to fluctuate. I'm at 1005 cycles and my health is at 93%. Is there something wrong with my late 2009 MBP or is this just the new standard with apple's batteries?
     
  4. miles01110 macrumors Core

    miles01110

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    Jul 24, 2006
    Location:
    The Ivory Tower (I'm not coming down)
    #4
    Because measurement is inherently innaccurate.
     
  5. paul117 macrumors regular

    Joined:
    Feb 17, 2012
    #5
    thats actually quite good... my 2011 MBP is on 85 charge cycles and the health is at 96% sometimes it changes to 97% or 94%.
     
  6. DoNoHarm macrumors 65816

    DoNoHarm

    Joined:
    Oct 8, 2008
    Location:
    Maine
    #6
    That's the thing. It seems too good to be true. I've recalibrated and everything. It just doesn't make sense!
     
  7. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #7
    Because battery readings are estimates, and as such, are not 100% accurate.
    No, there is no "standard" battery health.
    The built-in batteries in the newer Mac unibody notebooks come pre-calibrated and do not require regular calibration like the removable batteries.

    This should answer most, if not all, of your battery questions:
     
  8. Puevlo macrumors 6502a

    Joined:
    Oct 21, 2011
    #8
    Just like your health in real life can fluctuate due to illness/disease etc, so can your Mac computer's battery health.
     
  9. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #9
    Except your battery health doesn't fluctuate due to illness or disease or anything that indicates a problem. It's simply an inaccurate estimate.
     
  10. Dangerous Theory macrumors 68000

    Joined:
    Jul 28, 2011
    Location:
    UK
    #10
    The activity of electrons in each cell is always going to vary randomly, and resistors and capacitors throughout the circuit have a degree of error. In fact, there are so many small things that contribute to an inaccurate reading.
     
  11. FWRN macrumors member

    FWRN

    Joined:
    Apr 10, 2012
    Location:
    Portland, OR
    #11
    I don't know if it's good or not, but on my Late 2008 Macbook Unibody, I'm at 1997 Cycle Count and the condition is normal...
     
  12. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #12
    Have you calibrated it properly? See the Battery FAQ for instructions.
     
  13. FWRN macrumors member

    FWRN

    Joined:
    Apr 10, 2012
    Location:
    Portland, OR
    #13
    Once every 6 months...
     
  14. GGJstudios macrumors Westmere

    GGJstudios

    Joined:
    May 16, 2008
    #14
    It should be every 30-60 days. Try calibrating again.
     
  15. Interstella5555 macrumors 603

    Interstella5555

    Joined:
    Jun 30, 2008
    #15
    [​IMG]

    It's alive!!!

    Well, kind of, the battery health will fluctuate like other things based on environment, current state, etc.
     

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