dymar

Q: Will MacBook Pro battery stay at 100% when on charger or eventually start to drop?

When a MacBook Pro remains connected to the charger, will the battery stay at 100% (or whatever level it was when the charger was connected) or will it eventually start to drop?


I seem to recall having read articles stating that the battery eventually starts to lose charge even while connected to the charger, but some Apple Store personnel have said the level shouldn't decline at all as long as the charger is connected.


I am sure that the level used to drop when on the charger with older Macs -- at least it always did on my old MacBook (i.e., drop to 95%, then begin recharging again).  The question is whether that's no longer the case because of battery modifications that have been made since.  I use a mid-2012 MBP running Mavericks.


Thanks.

MacBook Pro, OS X Mavericks (10.9.5)

Posted on Sep 4, 2015 3:00 PM

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Q: Will MacBook Pro battery stay at 100% when on charger or eventually start to drop?

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  • by dymar,

    dymar dymar Sep 5, 2015 7:34 AM in response to TheSnapDude
    Level 1 (4 points)
    Mac OS X
    Sep 5, 2015 7:34 AM in response to TheSnapDude

    TheSnapDude wrote:

     

    If the battery is healthy it will stay at 100% when fully charged.  If the battery is defective or just really old and failing then it will show 99% (that's what happened to my old battery).

     

    Check the status of your battery by holding down the Option key, and then clicking once on the battery icon in your upper right screen menu (where you see your WiFi logo).  It will tell you the condition.

     

    Thanks, but my indication of a problem was specifically the battery staying at 100% while on the charger, and it turned out that there was in fact a problem.

     

    Whether or not that was a coincidence remains to be seen.  (I should know soon and will report back.) 

     

    Prior to that, my battery, when fully charged, stayed at 100% for perhaps several days, but then began to decline to 95% (MBP still on the charger), after which it would move back to 100%.  That was the expected behavior based on all the Apple documentation I had read up to that point.

     

    I disagree that Option-click (on the battery icon) is always reliable.  It isn't.

  • by Grant Bennet-Alder,

    Grant Bennet-Alder Grant Bennet-Alder Sep 5, 2015 7:49 AM in response to dymar
    Level 9 (61,322 points)
    Desktops
    Sep 5, 2015 7:49 AM in response to dymar

    running exclusively on the charger will lead to overcharging and battery burst.

    They are misinformed.

     

    OGELTHORPE's comments above were in the context of 'battery charge decline in system with power adapter connected'. I expect he would agree (and has previously posted the advice) that your Mac should be "exercised" off the charger at least once a month. Including ALL the advice required for every situation in response to a narrow question would lead to 'book-length' answers to every question.

     

    apple has revised their previous glossy article on notebook batteries, and laundered out much of the advice previously found there:

     

    About Mac notebook batteries - Apple Support

     

    some of the previous advice now appears here:

     

    http://www.apple.com/batteries/maximizing-performance/

    .

  • by OGELTHORPE,

    OGELTHORPE OGELTHORPE Sep 5, 2015 8:36 AM in response to dymar
    Level 9 (52,700 points)
    Mac OS X
    Sep 5, 2015 8:36 AM in response to dymar

    dymar wrote:

     

    Apple's own documentation (at least all the online help pages I've read) have always stated that a laptop battery needs to be exercised and should not be run exclusively on A/C.

     

    Absolutely correct.  One of my golden rules is if the MBP is connected continuously to AC, at least once per month, use it under battery power to about the 40% charge level before reconnecting to AC.

    dymar wrote:

     

    Can you document your claim that it's ok to keep the charger connected at all times?

    You are just reading more into what I wrote.  All I am describing is what will happen in those circumstances if those conditions are maintained, not suggesting that is desirable.  Perhaps I should have added my aforementioned golden rule.  (The other rule is to avoid deep discharges which will shorten the battery life.)

     

    @ Grant Bennet-Alder:  I appreciate the affirmation. 

     

    Ciao.

  • by dymar,

    dymar dymar Sep 7, 2015 2:19 PM in response to Grant Bennet-Alder
    Level 1 (4 points)
    Mac OS X
    Sep 7, 2015 2:19 PM in response to Grant Bennet-Alder

    Grant Bennet-Alder wrote:

     

    running exclusively on the charger will lead to overcharging and battery burst.

    They are misinformed.

     

    OGELTHORPE's comments above were in the context of 'battery charge decline in system with power adapter connected'. I expect he would agree (and has previously posted the advice) that your Mac should be "exercised" off the charger at least once a month. Including ALL the advice required for every situation in response to a narrow question would lead to 'book-length' answers to every question.

     

    apple has revised their previous glossy article on notebook batteries, and laundered out much of the advice previously found there:

     

    About Mac notebook batteries - Apple Support

     

    some of the previous advice now appears here:

     

    http://www.apple.com/batteries/maximizing-performance/

     

    Post-Genius Bar report:

     

    Apple Store Genius says that the batteries in MacBook Pro's from recent years do not need to be exercised as did batteries in earlier laptops.  The recent models can be left on the charger as much as the user desires (including all the time) with no adverse effects.

     

    He also said that except when usage causes unusual loads on the processor, the battery will show 100% until the machine is used on battery power. 


    I can't rule out the possibility, perhaps even the likelihood, that the same inquiries might be answered differently by other Apple Store Geniuses.

  • by dymar,

    dymar dymar Sep 7, 2015 2:20 PM in response to OGELTHORPE
    Level 1 (4 points)
    Mac OS X
    Sep 7, 2015 2:20 PM in response to OGELTHORPE

    Thanks.  See reply to Grant Bennet-Alder above.

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