Drain mbp battery or keep charging?

Discussion in 'MacBook Pro' started by KSaebin, Oct 2, 2010.

  1. KSaebin macrumors newbie

    Oct 2, 2010
    I'm wondering, what is better for prolonging your macbook pro's battery life, is it

    1. drain the battery, recharge it fully, plug out the source, drain it, and recharge it again


    2. keep charging it whenever you have a power source and never drain it?

    I've always been doing #2 because I use the laptop a lot and home and it would just be a hassle to keep switching the power source on and off.
    But then I heard that it's bad if you overcharge your battery, so once in awhile I try to do #1. Last night, though, my friend told me it's bad for your battery if you drain it all the time.

    So which is, in fact, good or bad for your mbp?

    Thanks in advance!
  2. uncletoby macrumors newbie

    Sep 16, 2010
    Conventional wisdom says, drain a battery as far as you can, charge it as far as you can, that keeps it healthy.

    I can't find the link, but Gizmodo did a long piece recently explaining the science of batteries, and basically, the conventional wisdom isn't quite right. Overcharging a battery, and especially draining it too far to the end, put it through chemical strains that permanently lessen its electrical capacity. The un-conventional, but scientifically correct, ideal, is to keep a battery "middle-charged" as much as possible. It will not lose capacity just because you fail to exercise its extremes.

    I know Apple's battery management keeps a reserve and shuts a device down so it doesn't go below a true 10% charge, and I suspect the charging system shuts down when your MBP / iPhone / etc is near 100% to keep it from overcharging. So I think you are safe just using your MBP as you please. Worst case, you pay $150 and replace the battery after a couple of years. To me, that kind of fee is worth not obsessing over it. :)
  3. Perdification macrumors regular

    Sep 22, 2010
    Believe Apple : http://www.apple.com/batteries/notebooks.html

    Don't leave it plugged in all the time though, it kills the battery way faster than anything. Lithium based batteries can withstand half charges, that means you don't have to drain it fully before you charge. Just use it normally without worrying too much about it, but don't leave it plugged in always.
  4. toxic macrumors 68000

    Nov 9, 2008
    discharging it every time is pointless. just don't leave it plugged in for months at a time.
  5. GGJstudios macrumors Westmere


    May 16, 2008
  6. KSaebin thread starter macrumors newbie

    Oct 2, 2010
  7. Stingray454 macrumors 6502a

    Sep 22, 2009
    I honestly think this isn't a problem either. There are controllers for the charging that manages how to charge the battery when plugged in. It won't overcharge your battery. I used my MBP while plugged in for months at the time, and when running on battery I still got the specified battery time. Now I get slightly less, but the computer is 2 years old, so I guess this is perfectly normal.
  8. GGJstudios macrumors Westmere


    May 16, 2008
    Read the link I posted. Leaving your MBP plugged in for months at a time will shorten its life. It's not an overcharging issue. It's a lack of electrons moving.
    Have you calibrated, to make sure your readings are accurate? The calibration steps are also in the link I posted.
  9. Jack06 macrumors member

    Jul 11, 2009
    I usually, keep it plugged in (but sleeping) then when I want to use it, either on my desk or elsewhere I unplug it, usually the 2-3 hours of charge is more then enough for me to accomplish what I wanted to do. Then I just plug it in again.
    I usually leave it unplugged overnight as even after 10 hours sleeping it rarely falls below 96%

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