Plug in MBP all day harms the battery?

Discussion in 'MacBook Pro' started by colonel179, May 28, 2015.

  1. colonel179 macrumors member

    Jun 10, 2014

    I would like to know if having my MBP connected to a power surge all work day (8+ hours) would affect the battery or any other thing?

    Does it harm it in any way, or would it be better to unplug it and use the battery until it drains, then unplug it.
  2. magbarn, May 28, 2015
    Last edited: May 28, 2015

    magbarn macrumors 68000

    Oct 25, 2008
    lol, this one has been beaten to death. I wouldn't leave it plugged in 24/7. Lithium batteries like to be between 20-80% charge mostly for the longest life. In other words they don't like to be at 90-100% all the time when plugged in and they don't like to be discharged to 0% all the time either (although Apple does recommend to do this monthly so the battery can recalibrate.)

    They also like to be exercised once in awhile. I'm OCD so I've decided to a little trick with my MacBooks. For the ones that I don't take on the road, I use their batteries down to about 50%, I then put a little strip of electrical tape on the middle pin on the magsafe connector on the laptop. When this is done, the AC adapter will continue to power the macbook, but the battery won't be charged. I know it's an inelegant solution, but unfortunately Apple doesn't have a battery saver app like Lenovo. Lenovo's app is awesome, you can dictate at what percentages to start charging/discharging. That way you can keep the battery from being maintained at >90% all the time when plugged in which is harmful.

    Hint: It's easy if you use a magsafe 1 AC adapter on a magsafe 2 macbook, the tape goes on the magsafe 1 to 2 adapter...

    Just so you know I'm not just talking out of my ass here's a link below:
    Battery University

    Also, Hybrid car makers know this so cars like the Prius like to follow the rules above. They don't like to fully charge or fully discharge the batteries.

    Attached Files:

  3. Weaselboy Moderator


    Staff Member

    Jan 23, 2005
    Won't hurt a thing to leave it plugged in. Running it down intentionally like you mentioned actually puts unnecessary cycles on the battery.

    Take a look at these links for Apple's official battery information.
  4. ron1004 macrumors 6502


    Feb 6, 2010
    Louisville, KY
    My 2010 and 2011 17" MBP's stay plugged in 24/7 and only occasionally used on the batteries, and the batteries still run for much the same time as when they were new.
  5. savagewatts macrumors regular

    Oct 21, 2014
    Vancouver, BC
    I've had mine for almost a year plugged in most of the time. I still have 100% capacity.
  6. JackieInCo Suspended

    Jul 18, 2013
    In all my MacBooks and MacBook Pros, I've always kept them plugged in. I occasionally use them on battery power because if you don't use the battery enough, it can swell and show that it needs service.
  7. simonsi macrumors 601


    Jan 3, 2014
    My MBA has seen the same decline in battery capacity but over a shorter period than my MBP which typically gets a cycle a day roughly. IMHO they benefit from regular use.

    Li batteries swell due to chemical breakdown, that happens with age eventually in my experience.
  8. Evren Carven macrumors regular

    Evren Carven

    Dec 16, 2014
    From magbarn'reply, Lenovo has a battery saver app to manage what percentages to start charging/discharging. Is there a similar app for Mac? I think it is very useful for battery life.
  9. leman macrumors G3

    Oct 14, 2008
    It really doesn't matter what you do with your battery. It will most likely last 4-5 years independent of how you treat it. I constantly abuse my battery and its still doing fine after 3 years.


    I highly doubt that Apple exposes this kind of functionality. That would be agains their basic design principles.
  10. maflynn Moderator


    Staff Member

    May 3, 2009
    I have my 2012 rMBP plugged in all day when its not out traveling with me, or my kids grab it. The computer is now 3 years old and so far (knocks on wood) the battery is fine.

    My kids got the use of my old 2010 MBP and that's plugged in all day when its not in use, and that bad boy's battery is now 5 years old and its still going strong as well.
  11. snaky69 macrumors 603

    Mar 14, 2008

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