Can I drain until 46% and then shut down and turn on

Discussion in 'MacBook Pro' started by yourdream, Apr 27, 2010.

  1. yourdream macrumors regular

    Aug 16, 2008
    Can I drain the battery from 100% to 46% and then shut it down for the night? Then next day, turn it back on and drain it completely down to 0%? Does this count as calibration for the brand new battery on my MacBook Pro? Will it harm the battery in anyway? Or do I need to drain the battery from 100% to 0% while the computer is on and not asleep?
  2. miles01110 macrumors Core


    Jul 24, 2006
    The Ivory Tower (I'm not coming down)
    Just use your computer and don't worry about the battery. It's not going to harm it by draining halfway and then the rest of the way the next day.
  3. Gorilla Power macrumors 6502

    Gorilla Power

    Mar 19, 2010
    I presume you're talking about calibrating the battery ? You can drain it in intervals. Just make sure its either on or sleeping, ie. don't turn it off, and don't plug in the power while draining.
  4. trevorplease macrumors regular

    Feb 13, 2009
    Can someone post an even dumber guide than the apple support one? with like do's and don'ts of calibrating? I'm stupid.
  5. scaredpoet macrumors 604


    Apr 6, 2007
    trevorplease: Think of it this way: the battery and related software and circuitry assumes that you're very, very dumb. So dumb, that the fact that you're here, posting in this forum, means you're much smarter than the battery expects you to be. Of course this also means you're likely overthinking things.

    Given that, I really don't think you need to be calibrating a brand new battery on a brand new MBP. That's something they do for you at the factory, and there's little reason to think that the battery has gone out of spec from the time it left the factory, to the time it got into your hands.

    You should really only calibrate if you're seeing wildly out-of-spec battery life, and it's lasting way less on a charge than you think it should. Frequently calibrating and re-calibrating the battery not only prematurely ages your battery (by forcing unnecessarily deep charge/discharge cycles that you wouldn't otherwise be doing), but could increase the chances of an erroneous calibration reading if a cycle is interrupted.

    Only calibrate if your battery isn't acting the way you think it should. Otherwise, just follow these steps and you should be fine:

    Again: brand new MBP, I wouldn't calibrate it unless you know something's wrong. You also don't need to completely drain the battery every time. You can use it to 46%, and then charge it back up if you want to. With normal use, the battery should get plenty of exercise so long as you're not keeping the MBP plugged in 24/7.

    Fact is, I think the only time a calibration would be warranted is if you HAVE been keeping your MBP plugged in constantly for weeks on end. At that point the battery has been disused, and the MBP's calibration profile for it is inaccurate.

    Bottom line: As long as you use your battery regularly, you shouldn't have to worry about it all that much.
  6. Gorilla Power macrumors 6502

    Gorilla Power

    Mar 19, 2010
    Guide for dummies :p

    1. Charge your notebook till full. Green LED on the charger, "100% (Charged)" should show on the menu bar.

    2. Disconnect power, start using your computer normally till you reach low battery warning (normally at 10%). This doesn't however mean that you have to use it continuously, you can let it sleep in the middle. Just don't plug in the power all this time.

    3. Save your work when you get the warning.

    4. Let the computer die. It will go to sleep automatically when it can't take it anymore !

    5. Leave it to sleep for atleast 5 hours. I'll do 5 hours 30 mins. (Tip: plan such that the computer dies when you go to sleep at night, so there's no interference with your work. Its just like marinating chicken wings overnight ! :D).

    6. Plug the power in and recharge till full. Don't turn your computer on yet. Just let the LED on the adapter turn green before switching it on.

    And you're done ! I know the letting it sleep part is time consuming but its good for your machine.
  7. RaceTripper macrumors 68030

    May 29, 2007
    Not necessary. You can turn the computer on and use it while it recharges, as long as you let it reach full charge before going on battery power.

    Apple lists the steps for calibrating batteries.
  8. Gorilla Power macrumors 6502

    Gorilla Power

    Mar 19, 2010
    ..where it says

    Doesn't specifically mention:

    as in #2 in the document, or anything similar.
  9. RaceTripper macrumors 68030

    May 29, 2007
    Right, it says connect to the charger and leave it until fully charged. If you use the computer during that time, you're still following the instruction. There's no reason to read more into it. Go ahead and leave yours off while charging if you want, but that isn't the instruction. If it were Apple would be explicit about it.
  10. GGJstudios macrumors Westmere


    May 16, 2008
    Apple DOES recommend that you calibrate your battery when you first get it, and they DON'T recommend only calibrating when you think something's wrong.

  11. Gorilla Power macrumors 6502

    Gorilla Power

    Mar 19, 2010
    Not here to win an argument, but yes, that's what I'd do.

    Logic behind it is not to interrupt the (reverse) flow of electrons during calibration when the battery recharges back. The instant you start up your computer the battery loses charge from the usage and gains charge from the power, which is a ++ / - process. The idea behind battery calibration is actually helping the computer better estimate its read parameters, which is achieved by making it "understand" a completely uninterrupted discharge (--) (just as you don't plug in the power on your way down) and a completely uninterrupted recharge (++) which is why I wouldn't jump on using it after its slept for 5 hours. It isn't that hard.
  12. trevorplease macrumors regular

    Feb 13, 2009
    Anyone object to Gorilla_power's comment? If not then that's how I'll be calibrating my battery!

    Thanks for the help guys

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