macbook pro + led cinema display concern

Discussion in 'MacBook Pro' started by bchamorro, Mar 7, 2010.

  1. bchamorro macrumors regular

    Joined:
    Dec 31, 2007
    #1
    I just got a MacBook Pro and an LED cinema display 24'' and I find myself using it 90% with the cinema display in clamshell mode. I am worried because the power adapter of the cinema display is charging the battery 24/7 when it is charged and i am afraid it might damage it. I can't use the LED cinema display without powering the macbook pro.
     
  2. stridemat Moderator

    stridemat

    Staff Member

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    Apr 2, 2008
    Location:
    UK
    #2
    The battery on your Macbook pro should work fine like this. I run my whitebook in clamshell mode most of the time. I just cycle the battery every month or so to keep it healthy.
     
  3. bchamorro thread starter macrumors regular

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    Dec 31, 2007
    #3
    you mean let it drain completely once every month?
     
  4. stridemat Moderator

    stridemat

    Staff Member

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    #4
    From this Apple support document, in essence you run the battery down until the low power message appears and then fully recharge it.
     
  5. rasmusDoh macrumors regular

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    Nov 30, 2009
    #5
    Have read a lot of stuff about keeping your battery healthy,
    but i just bought a ACD too (haven't gotten here yet).

    You sure it's keeping the battery perfectly healthy when only completly draining it once a month?

    I mean, if more is needed i'll have no problem unplugging it overnight or something, just to take fully care of my baby! ;)
     
  6. stridemat Moderator

    stridemat

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    #6
    Thats what the Apple support document suggests!
     
  7. Pax macrumors 6502a

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    Dec 12, 2003
    #7
    Don't worry about it. Just because the Magsafe is plugged into the Mac, doesn't mean it's charging the battery.

    About 1 hour after the Magsafe LED turns green, the battery stops charging. After that the Mac is powered just from the Magsafe. The battery is isolated from the system. If you leave the Mac like this, after a few days or weeks the charger will add a little top up charge to the battery.

    So leaving the Mac plugged into the Magsafe is no different to unplugging it. The charger is very smart and will look after your battery as well as possible.

    Read the Apple article carefully. It does not say do this to keep the battery healthy. It says "The battery needs to be recalibrated to ... keep the onscreen ... display accurate and to keep the battery operating at maximum efficiency"

    Calibration is more about accurately estimating how much charge the battery can hold. It's like having a car with an inaccurate gas gauge, and a tank whose size varies with time. The only way to really know how much gas the tank can hold is to empty it completely, and then fill it up noting how many gallons it takes.

    The battery on my Macbook is 3 years old, 400 plus cycles and it's never been calibrated. It's still at 90% plus capacity, and it still runs the computer for 3 hours or so.
     
  8. rasmusDoh macrumors regular

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    Nov 30, 2009
    #8
    Pax -> Don't know anything about the 3 year old MacBooks, so can you please tell me if 3 hours is close to the advertised / original battery life of that model? :)
     
  9. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #9
    I think so, it certainly hasn't got any worse over time. It never did 4 hours when new, so 3 hours is pretty unchanged.

    You have to get to thinking that the battery is a disposable item. If you are lucky it will go 5-6 years. If you are unlucky it might only go 2. It might cost $150 to replace, so on average it will cost you maybe $30 per annum. Not worth losing sleep over. You will probably spend more on printer ink. If you can afford an ACD you aren't worried about $30 per annum!!!!!

    There is very little you can do to influence the life of your battery. The charge circuit in your Mac takes very, very good care of the battery (remember, if you treat Li-poly batteries badly they tend to explode). But even so it might only last 2 years.

    Think of batteries like car tyres. You could put a fantastic new $150 tyre on your car today, and get a blowout tomorrow. There is very little you can do about it except not drive the car anywhere.

    Just get on your Mac and drive. Don't worry about the battery. Just keep water and Coke away from it, and don't drop it.
     
  10. rasmusDoh macrumors regular

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    Nov 30, 2009

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