MacBook Battery Callibration - More harm than good?

Discussion in 'MacBook' started by NikMac, Sep 16, 2008.

  1. NikMac macrumors member

    Feb 9, 2008
    Hi everyone.

    I've had my MacBook since late May and calibrated it twice (using the steps on apple's site). It seems like after each calibration, the battery "health" gets slightly worse. According to coconut battery and iStat pro, after the first callibration the overall capacity dropped from 5059 mAh to 5004 mAh (99%). Then it rose a little to 5013 mAh over time, and eventually rose again to 5026, then dropped back to 99%. Now, after the second calibration it's dropped to 98% at 4968 mAh. Sorry if that didn't make sense :p.

    The point is that the battery was at 100% until after first calibration when it dropped to 99%, now after the second it's dropped to 98%. I know 2% isn't much to fuss about, but will it keep dropping after each calibration, even though the point is to extend battery life?

    In 4 or 5 months I've only gone through 5 battery cycles (including two calibrations). I leave it plugged in most of the time, perhaps running on battery power until it's at about 80% and then plugging back in. Is there something I should do, or keep using it as normal? It's still kind of new, so I don't want the battery to die suddenly.

    Thanks :D
    (also, while on the subject of batteries, my iPod's having issues. I'd appreciate someone taking a look at ;) ).
  2. priller macrumors regular

    Dec 15, 2007
    Never calibrated mine & I'm still getting 4-5 hours battery life.

    Attached Files:

  3. ksabek macrumors member

    Sep 15, 2008
    about the calibration thing I don't know I only calibrated it once till now and my battery is fine, I have went through 22 cycles in less than a month because of what I heard about laptop batteries is that you should always use their battery till the end then charge fully then remove from charge, you shouldnt keep ur laptop connected to the plug while the battery is fully charged!!
  4. misterredman macrumors 6502a


    Oct 3, 2007

    It's probably normal, since the calibration will make the system show the true capacity of the battery. In fact that is the purpose of the calibration: to make the system aware of the true capacity, so that it will be able to enter sleep not too soon and not too late (i.e. when there is not enough energy).

    Also keep in mind that the capacity value indicated fluctuates, and it's not something to be worried about. Of course if you notice a bigger drop in capacity after a calibration you may have to talk with Apple.

    As far as leaving it plugged in all the time I see no problem, but you will have to use the battery from time to time, as explained here:
  5. Mauricio N. macrumors newbie

    Sep 17, 2008
    Hi there! Since we're talking about the MacBook battery, I'd like some suggestions concerning my battery as well... 4 months ago, I had to replace my MB battery, after 2,5 years of usage (around 320 charge cycles), and just today this new battery of mine had its health decreased from 100 to 93% (currently at 84 charge cycles), all of a sudden. Just to give a usage background, I always unplug the AC cord when it's 100% charged, and I only plug it back when the low battery warning pops up. Also, a weird thing happend today (1st time for this new battery): the charge indicator went from around 10% to 0, putting my MB in standby mode, without any low battery warning.
    So, what you guys think? Should I replace this new battery already?
  6. aquajet macrumors 68020

    Feb 12, 2005
    To answer your first question: no, there is no reason to replace your battery. Nothing is out of the ordinary.

    With that said, the important thing to remember is that battery calibration actually means battery meter calibration. That is, the time remaining estimate in your menubar must be calibrated to the actual battery capacity (also known as battery health) before a proper estimate of your actual runtime can be performed. This is done by draining the battery until it sleeps.

    The reason why your battery meter went from 10% to 0% suddenly is because the time remaining estimate was not calibrated to the actual health of your battery. When your battery meter is properly calibrated, the computer will estimate how much remaining runtime you have available based on the battery's estimated health against the amount of current that the computer is drawing from the battery. The actual determining factor of when the computer will sleep due to a depleted battery is done once the battery's voltage drops below a certain threshold. This occurs because the battery is no longer able to supply the electrical current demand placed on it by the computer, and thus the voltage drops to a level below what the computer requires for operation.

    So in effect, what just happened is that you unwittingly recalibrated your battery's meter. Because the computer thought the battery had more capacity than it actually did, it was forced to sleep despite what the time remaining estimate (the percentage in this case) reported. That's why your battery health now indicates a lower amount -- because it is now calibrated to the actual battery health.

    In all likelihood, your battery's health didn't actually drop suddenly, but rather it slowly degraded over time and never had a chance to properly calibrate itself to the time remaining estimate. This is the reason why battery meter calibration should be performed regularly -- so that your computer doesn't sleep unexpectedly.
  7. chrisiw macrumors regular

    Aug 22, 2008
    Isle of Wight UK
    My MacBook is 20 months old, i always leave plugged in when using at home and have complete recycled it about 8 times and it is still showing 100% and is showing 186 recharges, so for me it seems ok to leave it plugged in when you can.
  8. NikMac thread starter macrumors member

    Feb 9, 2008
    Thanks for the posts, everyone. So I guess for now I should keep on leaving it plugged in *most* of the time, and calibrating once a month? (or unplug whenever possible, as someone suggested)?

    And thanks for clearing up that it's actually the battery "meter" calibration.

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