This forum's battery guide: Conflicting & possibly wrong about cycling & discharging

Discussion in 'MacBook Pro' started by Libertine Lush, Mar 1, 2010.

  1. Libertine Lush macrumors 6502a

    Joined:
    Nov 23, 2009
    #1
    In anticipation of picking up a MBP when they're eventually refreshed (though I'll wait a couple weeks to see if there are any reported problems, as I went through 4 defective 27" iMacs recently), I was reading about battery use/care in a forum thread. Then I just checked the Laptop Battery Guide ( http://guides.macrumors.com/Laptop_Battery_Guide ) listed at the topic of this forum section and found 2 issues I'm curious about:

    1) There are 2 differing explanations of what a battery cycle is. In the "What is "full cycle"?" section, it says that a "cycle is when the total battery power is less then 50% before it is recharged." But in the "What this means" section, it says "every time your fully deplete the power equal to one maximum charge, your battery has gone through one cycle." Which one appropriately describes a full cycle?

    2) The guide also says that "it is best to fully drain the battery before you charge it up again." However, this site ( http://www.batteryuniversity.com/parttwo-34.htm ) says the opposite. That lithium ion batteries prefer "a partial rather than a full discharge. Frequent full discharges should be avoided when possible." Is the forum guide incorrect?

    Thank you.
     
  2. miles01110 macrumors Core

    miles01110

    Joined:
    Jul 24, 2006
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    The Ivory Tower (I'm not coming down)
    #2
    The latter.

    It is correct, but Macbook Pros don't use the technology that was around in 2006 when that article (batteryuniversity) was written. With the new Li-Poly batteries the effect of full discharges is mitigated significantly.
     
  3. Libertine Lush thread starter macrumors 6502a

    Joined:
    Nov 23, 2009
    #3
    When you say, "it is correct," are you referring to the forum guide?

    I didn't realize there's another type of lithium battery. So with the Li-poly batteries, which set of instructions should I be following--the forum guide or the batteryuniversity site?

    Thanks.
     
  4. Bill Gates macrumors 68020

    Bill Gates

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    127.0.0.1
    #4
    Don't discharge your battery completely except to calibrate it. "Mitigated" or not it's still harmful.
     
  5. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #5
    Re (1) I think Apple changed its definition sometime in the last few years, the forum guide is obsolete. The Apple site today says the latter is correct (there's a useful battery care page on Apple's site). And the way the cycles count on my MBP works the way Apple says. However I do distinctly remember my old Mac using the obsolete forum definition.

    Re (2) I think the forum guide is completely incorrect. It has never been the case with Li-ion or Li-poly batteries that full drainage is good for the battery. In theory you should keep your battery between 20% and 80%, but in practice I think miles01110 is correct - Li-poly is virtually bomb-proof and you should still get 1000 cycles regardless of how you treat your battery.

    Remember if you are a light to medium battery user you probably go through 1 cycle every 2 days, a 1000 cycle battery should last you 6 years - the useful life of the computer. There are plenty of posters on here with many hundreds of cycles on their batteries and still >90% capacity.

    And even if you do need a new battery after 6 years, that's an approx $100 item, cost less than $20 per year. IMHO that's not worth worrying about, in particular it's not worth doing some dubious battery voodoo to squeeze another few hundred cycles or $10 per annum out of the battery. Just use your battery as you see fit.
     
  6. Erasmus macrumors 68030

    Erasmus

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    Jun 22, 2006
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    Hiding from Omnius in Australia
    #6
    I think the biggest thing is keeping your battery reasonably cool.
     
  7. Libertine Lush thread starter macrumors 6502a

    Joined:
    Nov 23, 2009
    #7
    Thanks for all the replies.

    Thank you for pointing out that there's a Apple page on this. Here it is ( http://www.apple.com/batteries/notebooks.html and http://www.apple.com/batteries/ ) for any one reading that may be interested. And another thanks for mentioning that the cycle capacity of the new built-in batteries are in fact 1000 now. Wouldn't have noticed that on the Apple site had you not brought it up. The 300 cycle capacity listed in the forum guide had me a bit concerned. 1000's good.

    So I'll just get the Coconut Battery app mentioned in the guide, remember to do "a charge cycle at least once a month" (as suggested on the Apple site, which can be as simple as using half a charge one day, recharging, then using half again another day) and consider that sufficient for my battery maintenance.
     

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