Macbook battery health too low

Discussion in 'MacBook' started by Zillicah, Jan 31, 2010.

  1. Zillicah macrumors member

    Joined:
    Apr 12, 2009
    #1
    My white unibody macbook battery that I just bought has a battery health of 92% and it only has 23 cycles. I got this information from iStat Pro
     
  2. Zillicah thread starter macrumors member

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    Apr 12, 2009
    #3
    How is 92% battery life fine with 23 cycles? my aluminum macbook is at 98% battery life and it has a lot more cycles than this.
     
  3. bsblvnv macrumors regular

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    Jan 29, 2010
    Location:
    Las Vegas
    #4
    Mine is at 99% with 21 cycles, from coconut battery.
     
  4. Zillicah thread starter macrumors member

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    Apr 12, 2009
    #5
    this is not good because if it continues at this rate i will have no more battery left!
     
  5. miles01110 macrumors Core

    miles01110

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    The Ivory Tower (I'm not coming down)
  6. carlosbutler macrumors 6502a

    carlosbutler

    Joined:
    Feb 24, 2008
    Location:
    London City
    #7
    Battery health should stay at 100% for about 350-400 cycles. Apple (watch the battery video) even say that themselves. I have only had 49 cycles, and of course 100% health.

    Take it back to where you got it from, and just ask for a replacement.
     
  7. ucaggie macrumors newbie

    Joined:
    Feb 12, 2005
    #8
    I have the new uMacbook as well and don't worry...I had the same concerns and I had 12 cycles with 92% battery. About 10 days later, I'm at 17 cycles and 96% battery, with battery capacity raising steadily over the last few days. You might have to give it a few more cycles for the battery to give you the true reading.
     
  8. adztaylor macrumors 68000

    Joined:
    Aug 20, 2009
    Location:
    Preston, UK
    #9
    Have you calibrated the battery?

    Mines still at 100% with 162 cycles.
     
  9. andrutzik89 macrumors newbie

    Joined:
    Feb 25, 2010
    #10
    Hello. I have a similar problem. I have my mac for only 5 days, it has only 7 cycles and the health dropped to 95%. I charged this as apple says (waited until it went to sleep and then fully charged, every single time!). Do you have any idea why this happens?
     

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  10. deraj090 macrumors regular

    Joined:
    Feb 18, 2010
    #11
    subscribed.

    had my unibody for less than a week, and mine keeps going back/forth between 99-100%. Also, the capacity is steadily dropping.

    Luckily for us, these types of symptoms will occur well within the 1-year warranty (I didnt go with apple care yet).
     
  11. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #12
    Don't Panic!

    Keep an eye on it, it will probably wander up and down. Try calibrating.

    The actual capacity is just a guess.
    The battery charging circuit doesn't know exactly how many mAh are in the battery. It can only keep track of how many mAh are taken out and put in. By doing this it estimates how many mAh are in the battery at any time. It tries to measure the battery voltage to get a better estimate, but that's quite inaccurate. When you fully charge your battery it has to guess when to stop charging. It might get it a bit wrong.

    But these estimates gets less accurate with time. That's why calibration is useful once in a while. Calibration just means charging the battery right up to 100%, running it down to 0%, and counting how many mAh come out. Then the Mac knows (a) how many mAh fit into the battery and (b) what voltage corresponds to "full". Calibration gives more accurate charging but isn't anything magic.

    It's like a bank account where you can never see the balance, just money going in and out. Over time your estimate of the balance might get less and less accurate. The only way to find out what the balance really is, is to go to the ATM and keep taking money out until it stops letting you! Then if you put all that money back in, you'll know your balance exactly.

    Over time you will see the estimate of max capacity wander about a bit. If it differs a lot from 5100 mAh or whatever the start point is, it's time to calibrate.
     
  12. paddyhazard macrumors regular

    Joined:
    Jan 27, 2010
    Location:
    London
    #13
    With modern batteries (NiCd) this is actually more damaging to the battery to run it down completely then fully charge it up. It is alright to do this once in a while to calibrate the battery % and health but for general use it is better to keep it between 20-80% full and not complete full cycles all the time.

    This is something carried over from the old batteries (can't remember the chemical name of these but these types of batteries aren't used for phones and laptops and haven't for years)

    My MBP varies from 94%-96% battery health on about just <100 cycles. I'll wait till about 400 cycles and see how the battery is then to see if it's a dud and needs replacing by apple.
     
  13. deraj090 macrumors regular

    Joined:
    Feb 18, 2010
    #14
    Nickel Cadmium?

    It's tough for me to keep mine between 20%-80%. I usually take it off the charger when I'm using it, but when I'm not using it, I put it back on the charger, which keeps its at 100%... Solutions?
     
  14. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #15
    Solution - Forget about it!

    Just don't worry about it. The battery circuit will manage it and take care of it. It's fine.

    Lots of useful stuff here.... http://www.batteryuniversity.com/partone-12.htm

    "No trickle charge is applied because lithium-ion is unable to absorb overcharge. A continuous trickle charge above 4.05V/cell would causes plating of metallic lithium that could lead to instabilities and compromise safety. Instead, a brief topping charge is provided to compensate for the small self-discharge the battery and its protective circuit consume. Depending on the battery, a topping charge may be repeated once every 20 days. Typically, the charge kicks in when the open terminal voltage drops to 4.05V/cell and turns off at a high 4.20V/cell"

    When the battery is at 100% charging will stop, the battery will be fine. Every few days the charger will kick in and give it a small boost. That's why the maximum capacity can vary from 90 - 100% over a few weeks. Doesn't mean your battery is failing.

    My old Macbook has been plugged into the charger and kept at 100% for nearly all the 4 years I have had it. The battery capacity is still at 95% or something.
     
  15. deraj090 macrumors regular

    Joined:
    Feb 18, 2010
    #16
    Pax, thanks. That's exactly what I assumed. I think Mac provides TOO much information, causing this paranoia. On my old laptop (HP 12-cell battery), I left it plugged in, and would run on battery when needed. Didn't do anything special, or any kind of calibration, and the battery still lasts 5+ hours to this day (after 5+ years).
     
  16. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #17
    Yeah, I think you're right. Also there's a lot of well-intended mis-information on these forums.

    I never take any care of my computers or cars, they still last for ages and ages.
     
  17. deraj090 macrumors regular

    Joined:
    Feb 18, 2010
    #18
    couldn't agree more. I read a review about the different LCD manufacturers, and how two of them (one of which I ended up having) have a blue hue, while a third is more of a pure white... it almost drove me nuts -- and then i realized that's prettty much a complete opinion, and all depends on how your eyes react to certain light. not to mention, its adjustable if you want to go through the process...
     
  18. sml238 macrumors regular

    sml238

    Joined:
    Feb 26, 2010
    #19
    mines only at 46 cycles and it fluctuates from 89% to 99% i was told this is normal..
     
  19. paddyhazard macrumors regular

    Joined:
    Jan 27, 2010
    Location:
    London
    #20
    The tip i have been told for not keeping your battery at 100% and constantly plugged in helps reduce heat in the battery. Charging your battery makes it hot and intensively using your cpu or harddrive also causes a lot of heat. If you do the two together, you computer gets very hot and heat damages lithium-ion batteries a lot. I'd only unplug my laptop if i am doing something very cpu intensive to try and reduce heat build up.
     
  20. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #21
    Not true. The charger stops charging the battery after it's "full". Then the charger only kicks in once a week or so to top it up. Leaving it on the charger will not change the heating at all.

    Not really true, Li-ion charging is very efficient, you are charging it at about 20 Watts, much much less than 1 Watt is dissipated in the battery. Not enough to heat it significantly.

    Yes, your CPU helps heat up the battery, but whether you have the computer on the charger or not has almost no effect.

    Of course if you unplug the computer to do CPU intensive stuff you will use up more of your battery's cycles, it is only specified for about 1000 cycles. On the other hand if you leave it on the charger you will not be using any battery cycles. Just use your computer as you wish, the battery will last years and years.

    The true answer is:- Li-ion / Li-poly batteries are very tough, not like in the old days. And the chargers are very smart. You can do almost anything you like to them without affecting their lifespan. The only things you can do to improve their lifespan are IMHO pointlessly complicated and probably ineffective.
     
  21. paddyhazard macrumors regular

    Joined:
    Jan 27, 2010
    Location:
    London
    #22
    Whilst i accept that modern batteries and charging techniques are pretty much foolproof and that you don't need to do anything to prolong the life of your battery - i was just repeating what i heard from one of my product design lecturers said a while back who has worked in the electronics design industry for ages - where is your proof for those numbers. How can the battery charge at a maximum of 20 watts when the chargers for them are 60 and 80 watts. Also only loosing 1 watt out of 20 as dissipated heat would make the whole battery and charging system about 95% efficient which is ridiculous. Electronics will never become that efficient as a system, that is why you have the heat problems in the first place.
     
  22. uzit macrumors regular

    Joined:
    May 15, 2008
    #23
    According to Coconut, my brand new just open white macbook is 8weeks old with 8 charges!? :S
     
  23. Pax macrumors 6502a

    Joined:
    Dec 12, 2003
    #24
    My MBP charges at about 1500 mA (according to System Profiler) and ~12 V, that's ~18 W.
    You probably want to do some back of the envelope sums as well... it's a 60 Wh battery (I think), it takes about 3 hours to charge from dead empty. Do the math....

    Also http://www.batteryuniversity.com/partone-12.htm
    "The charge efficiency is 99.9% and the battery remains cool during charge"
    So only 0.1% * 18 = damn all watts are dissipated as heat in the battery
    You can find lots of other links confirming this

    The Magsafe adapter has to charge the battery AND run the computer.....
    = 18 W to charge battery
    + 35 W to run CPU
    + 10 W for GPU
    + 4 W for LCD at full brightness and other
    =67 W. My Magsafe is 60 W, so I guess if I am playing WoW my battery will take a bit longer to charge.

    "there's a lot of well-intended mis-information on these forums"
     
  24. paddyhazard macrumors regular

    Joined:
    Jan 27, 2010
    Location:
    London
    #25
    I stand corrected, that makes sense. I always thought that if you were charging and using a laptop all of the power was going through the battery to the rest of the system. I didn't know that it got split.

    Is that 18W an average or maximum for the charge though as doesn't the battery fast charge at a much higher rate for up till 80-90% or something?
     

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