When the battery on my Macbook Pro is fully charged, should i unplug the power cord?

Discussion in 'MacBook Pro' started by KingMo, May 27, 2010.

  1. KingMo macrumors member

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    May 27, 2010
    #1
    Hey guys, I just got my new Macbook Pro 15 (Mid 2010) laptop a few days ago, and i would just like to know if, when I charge my battery and it's fully charged, should I immediately unplug the power cord or can I leave it? What is the safest and best thing to do?

    ...Thanks for ur help guys.
     
  2. GGJstudios macrumors Westmere

    GGJstudios

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    #2
  3. appleguy123 macrumors 603

    appleguy123

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    #3
    No. You will add cycles and void your battery's warranty more quickly. Apple also has an adaptive charging system to stop damage from occurring to the battery if you dot unplug it.
     
  4. waynema macrumors member

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    #4
    leave it plugged in. For maintenance, have your battery calibrated at least once a month.
     
  5. sammich macrumors 601

    sammich

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    #5
    It's as simple as this: using your battery is bad. Leaving it plugged in doesn't use the battery. EDIT: and yes, it's recommended you fully use the battery once a month.
     
  6. psingh01 macrumors 65816

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    #6
    The battery doesn't have it's own warranty, it's covered under the same 1yr warranty as the rest of the machine. You'd have to try really hard to go over the 1000 or so cycles that they claim for the battery life in that first year. Though I will agree to just leave the machine plugged in.
     
  7. GGJstudios macrumors Westmere

    GGJstudios

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    #7
    Batteries are not covered by warranty, except in the case of defects.
     
  8. appleguy123 macrumors 603

    appleguy123

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    #8
    Apple traditionally doesn't cover the batteries with the normal warranty.
     
  9. Mark.W macrumors member

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    May 11, 2010
    #9
    This is the exact opposite of what a "genius" at the Apple Store told me. He said that even when the computer is plugged in and the battery is full, you are still running on battery power, which means that the battery is constantly draining and charging. In other words, there is no such thing as a "battery bypass" when the battery is full.

    My personal experience with [admittedly non-apple] laptops seems to support this theory. I used to have a Sony Vaio which was basically a desktop replacement and was plugged in 98% of the time. A year later, the battery was pretty much worthless.
     
  10. KingMo thread starter macrumors member

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    May 27, 2010
    #10
    Thanks

    Thanks a lot for ur input guys...i've been wondering about this for a while now...
    Btw, I'm a new mac user...switched from PC and I'm LOVING it.
     
  11. Deeya macrumors member

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    May 14, 2010
    #11
    The genius is wrong, when the battery is fully charged, there is no current being drawn from it.
     
  12. Mark.W macrumors member

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    May 11, 2010
    #12
    Then why does Apple recommend discharging the battery at least once a month? Is that purely for calibration purposes?
     
  13. dsprimal macrumors 6502a

    dsprimal

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    #13
    nice to know. on another note, my istat pro says my battery health is 98% and its fully charged. hmmmmmmm i wonder how long these batteries will last before we need to recharge every 2 hours or so (like my friends mothers old macbook, which literally drains from 100% to empty within 1 hour easily). is this normal for the health to go down? ive calibrated etc already, only owned this mbp for about a month.
     
  14. GGJstudios macrumors Westmere

    GGJstudios

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    #14
    Yes, calibration is recommended to be done every 30-60 days, to keep your battery's condition reporting accurate. The Genius wasn't a genius. The battery is not constantly discharging and recharging while plugged in. You can prove this by looking at the light on the MagSafe connector. It remains green when the battery is charged. If it goes back to charging, the light would turn orange.

    For more info, read the link I posted earlier.

    That's answered in the link, as well.
     
  15. dsprimal macrumors 6502a

    dsprimal

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  16. Inside_line macrumors regular

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    #16
    Not always true,

    Without batteries installed.... mac laptops run at reduced cpu frequencies. The power supplies are not meant to provide all of the power during peak loads... some juice does come from the battery, which is why the max frequency is reduced without it.
     
  17. GGJstudios macrumors Westmere

    GGJstudios

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    #17
    It's not drawing enough from the battery to reduce its charge to the point where it needs to be recharged, and it only draws from the battery during peak loads. Read what I said about the MagSafe adapter light. The reduced processor speed is a precaution. It doesn't mean that it's constantly drawing from the battery.
     
  18. Amasashi macrumors member

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    May 17, 2010
    #18
    The idea that leaving the power cord plugged in all the time is bad for battery life is something left over from the 90s and early 2000s. It simply doesn't apply now, unless you're buying dirt cheap products with no reputable brand name.

    Here's how it works from an engineering perspective. After your power cord is plugged into the computer, the wiring splits into two paths. One leads to the battery while the other goes straight to the logic board. Obviously this leads to 4 possible combinations of distributing power.

    1. Computer is off, plugged in, battery not fully charged. All the power from the outlet goes to the battery and it charges much faster.

    2. Computer is on, plugged in, battery not fully charged. Power is distributed accordingly between charging the battery and powering the computer. The battery will charge slower.

    3. Computer is on, plugged in, battery is fully charged. All the power will go to the computer, bypassing the battery.

    4. Computer is off, plugged in, battery is fully charged. No distribution of power, except for what it takes to power the green light on the MagSafe.


    Back in the old days, there weren't two paths for the power to travel after entering the computer, so the power always had to first go to the battery and then from the battery go to the computer. Thus, if you left the power cord plugged in all the time, you were effectively charging the battery to 100%, using it to 99%, charging it back up to 100%, and so on. There were also problems with overcharging the battery, but that's another story.

    Nowadays, it's no longer a problem, so you can leave your power cord for most electronic devices plugged in all the time unless it EXPLICITLY tells you not to, or if you bought a dirt cheap product that uses the old engineering method to save a few cents.
     
  19. Amasashi macrumors member

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    May 17, 2010
    #19
    I'm going to have to disagree. The power cord alone needs to be sufficient to sustain the maximum power usage of a machine. If anything, a computer will run slower when not plugged in and using just battery power.

    The rationale behind this is simple. If a power cord alone can't sustain maximum power usage, the computer needs to draw on battery power. What will happen once the battery is drained? The computer will simply shutdown even plugged IN? Not a chance.

    Maybe a Mac laptop does indeed run at reduced CPU frequencies without a battery installed, but it will be due to a reason other than the one you mentioned.

    Just FYI :)
     
  20. tombilske macrumors member

    tombilske

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    #20
    there are two reasons apple recommends not to run the computer only on battery power, one is that at peak loads of the cpu and hdd, the power cord is not always enough to power the computer and it draws a bit of power from the battery. that is why the CPU is clocked down if there isnt a battery in the computer, it states this on Apple's website. The other reason they recommend it is because if there is a power failure of the cord is pulled out, data loss is far more likely. but the CPU does run slower when there is no battery in the computer, apple designed it that way

    Edit: also, there is very little chance of you running your mac at 100% capacity until the battery is drained while its plugged into power. it doesnt draw much power form the battery, and its not for an extended period of time
     
  21. oHai macrumors member

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    Apr 1, 2010
    #21
    Good info in here - thanks for the replies.

    I used a (Windows) laptop as a desktop replacement for a while during college, and it was plugged in all the time. When I took it out on battery power (years later), I got an hour at best, and at the time I thought using the battery a lot was better for the computer. That mentality is seeping into my new MBP ownership, so I guess I have to fight it!
     
  22. Amasashi macrumors member

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    May 17, 2010
    #22
    Well you know, even if you leave it plugged in all the time, you should still calibrate the battery every once in awhile (Apple recommends once a month). Plus, you said yourself it was a few years later when you could only get an hour's charge. That was probably due to the natural aging process of the battery and not the fact that you left it plugged in all the time.
     
  23. GGJstudios macrumors Westmere

    GGJstudios

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    #23
    If you read the information in the link I provided in the 2nd post in this thread, you would know that your statement is not correct.

    From: MacBook and MacBook Pro: Mac reduces processor speed when battery is removed while operating from an A/C adaptor
    I think you meant to say "only on AC power, with the battery removed". Other than that, your statements are correct.
     
  24. iamrawr macrumors 6502

    iamrawr

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    #24
    Very helpful thank you. So is it still possible to overcharge a computer/device? If so, what happens to it?
     
  25. GGJstudios macrumors Westmere

    GGJstudios

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    #25
    No, it's not possible to overcharge your Mac. As already stated, it automatically stops charging when full.
     

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