MBP: Battery Life Tests

April 3rd, 2006

This post is part of the MacBook Pro Complaints series. Instead of (or in addition to) linking directly to this post, consider linking to the series link, which includes a summary of all findings to date and direct links to the pertinent downloads that users may find useful. Thanks for reading!

At this point we understand that a number of workarounds exist for the “CPU whine” noise bothering many MBP owners. What has remained unanswered, for the most part, is whether there is an impact, and if so how much, on the battery life when applying these workarounds. I have assumed that each of the workarounds takes away from battery life to some extent, but have been hard-pressed to declare with any confidence which is the “most efficient.”

Those days of uncertainty are over. At least, I’m ready to share my somewhat scientific results. So here is the experiment: “How long does it take a fully charged MacBook Pro to exhaust its battery to the point of forced sleep?” I applied this question to some of the workarounds I know of, and also to a control case: the MacBook Pro without any workaround (“with noise”).

So what did I do to make it “fairly scientific”? A few things. These are the preparations I made to the MBP, with the goal that battery drain should be as predictable as possible and therefore reveal any discrepancies caused by the underlying workaround. Since I have to wait around while this is happening, I also make no effort to achieve a particular long “control case” life:

  1. I configured the computer’s energy saving settings (for “Battery”) such that it should “never sleep” either the computer or display. I also unchecked the “Put the hard disks to sleep” option. These features all seem like they could add unpredictable savings to one test case while somehow not kicking in the same amount on another.
  2. I turned off Spotlight indexing for each of the 3 partitions on my MBP drive. Although Spotlight should only kick in when new files get added, I don’t want to take any chances that it suddenly decides to rebuild an entire index during the test.
  3. I turn the screen brightness up to high. Not only is this necessary for complete silence on my computer, it also helps drain the battery faster so I can get my answer.
  4. Before each test, I recharge the battery to 100% (and then some), and then restart the computer with the power cable attached. I then configure the particular workaround so that it is “active.” That is, the noise will not be audible during the test.
  5. After restarting the computer, I take care to run as little as possible. After enabling the particular workaround, I launch a small, custom application I’ve written which is designed to simply record the time it was launched and the time the computer was forced to sleep. As I launch the application, I pull the plug on the 100% charged battery, thereby starting the test.

The computer is left untouched in a corner of my office. After a few minutes the automatic screen saver kicks in, and continues to run until a couple hours later, when the power gets low enough that, despite my Energy Saver settings asking not to be put to sleep, the computer is forced to do so. Whenever I notice that the machine has actually gone to sleep, I plug the power back in and wake it up. The resulting difference in time between yanking the power and going to sleep is the “test result.” Now, I worried at first that the screen saver could be using enough CPU to essentially negate the power lost to QuietMBP’s CPU utilization technique, but the tests show that such concerns are unwarranted. QuietMBP’s impact on battery life is unarguably noticeable, despite the operation of a graphical screen saver for the bulk of the test time.

So, having hopefully described my test scenario sufficiently to make it interesting and respectable, here are my results, listed by name, brief summary, and time in hours, minutes, and seconds. The order is from “most battery life” to least, with the difference from the control case in parentheses:

  • Ear Plugs – Noisy MBP control case. 2:43:36
  • Single CPU – Disable the second core to minimize the noise. 2:28:04 (-15:32)
  • MagicNoiseKiller – Like the Mirror widget but no Dashboard involved. 2:27:58 (-15:38)
  • QuietMBP – CPU idle utilization. 2:17:26. (-26:10)

So, no doubt in my mind working around the problem costs battery life, but at least I have a bit more perspective on what I’m trading for my sanity. What’s interesting of course is that Single CPU mode appears to cost battery life: the same amount as MagicNoiseKiller! This has been anecdotally discussed on various forums, but I was curious to discover its apparent truth. My theory is that when both CPUs are running, the machine doesn’t have to work as hard to do “everyday stuff.” Probably when you disable a CPU, the remaining CPU works overtime to get the same work done, and this costs it more power.

Tests that will be less interesting but still worth trying when I get more time:

  • Photo Booth Visible – Photo Booth running in an open window.
  • iChat Video Hidden – iChat video preview on but minimized.
  • Mirror Widget – Classic “Magic” workaround, open and close Dashboard widget.

So what is the takeaway? The MacBook Pro is flawed, but you can make rational choices about which workaround has the least impact on your lifestyle.

If I can’t exploit the full battery life of my computer without distracting noises, then it’s no “professional” computer. I still don’t know what to do – I’m intrigued by suggestions like the one from Jasmine on a previous post, who suggests that perhaps the power supply just needs to have “epoxy poured on one of the coils.” If some kind of retrofix is possible, then I’d like to have the issue addressed when I send mine in for the screen inverter buzz. If they can’t fix it I may push for a (late) return, since I find the computer to be unusable without these compromising workarounds.

Those of us suffering the noise feel pretty helpless: we spent all the money and we have to sit and question the correctness of our decision. I don’t know if there is any value in online petitions or if this one is even the most appropriate one to target my signature to, but I signed it. Maybe it will help, and I don’t think it can hurt.

Appreciate the work I’ve been doing? It’s been my pleasure, but it’s true that I’ve spent a lot of time on this. If you want to show your appreciation in the form of a donation, I’d very much appreciate it. Whatever amount (so far they range from $5-$15USD) you feel is appropriate will be music to my ears, and it might help block out the sound of the MacBook Pro’s CPU whine :)

27 Responses to “MBP: Battery Life Tests”

  1. Kevin Ballard Says:

    You might be interested to read http://www.dailytech.com/article.aspx?newsid=1584

  2. James Bailey Says:

    You do know that the inverter whine indicated by your need to put the screen brightness on high to eliminate the LCD noise is something that AppleCare will fix? You do have to make sure that they understand that it is the LCD inverter whine and not the more difficult CPU noise, but they have fixed many MacBook Pros with this problem and I’m pretty sure on new MacBook Pros this noise is much rarer if not completely fixed.

  3. Mav Says:

    10.4.6 seems to stop MagicNoiseKiller from working. :(

  4. moiety Says:


    I came here to state exactly what Mav said above. MagicNoiseKiller ceases working as advertised under 10.4.6. The Mirror Widget still works, however. Seems like the mirror widget gas more magic than your solution for now.

    I hope you’re able to fix your app, since it’s convenient to have it as a login item!

  5. willi Says:

    yes, MagicNoiseKiller does stop working in 10.4.6. well, back to the old mirror hack.

  6. Mav Says:

    Actually, I’ve since discovered that if you just keep retrying MagicNoiseKiller it will eventually work. Basically, it no longer works 100% of the time but if you run it say five times in a row then chances are the noise will stop. So if it doesn’t work just run it again and again until it does.

    I still find running MNK (which I put on my dock) faster than opening up dashboard, dragging the mirror widget on and then closing it again… even though I now have to click the dock icon a few times.

  7. moiety Says:


    How very interesting. I opened up Photo Booth and closed it to have the whine start again, and this time around, MNK worked the first time. However, since it would appear that with 10.4.6, MNK needs multiple launches to work, this disqualifies it from use as a login item…

  8. moiety Says:

    Another update — the noise came back after a while, all by itself, after I had last stopped it using MNK. I think MNK is a lost cause under 10.4.6, as it has become unreliable. I’m sticking with the Mirror Widget until MNK gets fixed/updated.

  9. Allen Says:

    If you open Photo Booth then close it, and then run MNK, the whine goes away. I guess it’ll have to do for now :-/

  10. Andi Zeidler Says:

    hi daniel,

    first of all, thanks for all your work regarding these issues! unfortunately i’ve only been reading through your blog since i also have the “cpu whine” with my mbp (w8612xxx, btw). and while MNK is working for me with 10.4.6 i have another, possibly stupid question for you: when you’re talking about “Complete, beautiful silence.” after applying on of the workarounds, do you mean total silence like in no sound at all or is some — rather quiet — white noise coming either from the spinning harddrive or a fan regarded as “silence” here? :)



    ps: i haven’t been able to figure out if it’s the disk or a fan, since some process keeps writing a few bytes to the disk on a regular basis, preventing it from spinning down (even with “pmset -a disksleep 1”). is there any way to tell what processes are causing disk access? and while i’m at it: how can i tell… hah! now i guess you won’t believe it, but i’ve tried for half an hour or so to spin the hd down, and now while i’m writing down that very question it did… murphy’s law i guess. anyway, so that noise was indeed the hd running.

  11. Chris Alcock Says:


    Great work. MagicNoiseKiller is a god send. Just thought you might like to know (if someone hasn’t mentioned it already) that the CPU noise/whining sound does not occur when the MBP is booted under Windows XP.

    Kind regards,


  12. Trejkaz Says:

    QuietMBP by default pauses for 100ms between iterations and takes around 8% CPU. I have my own set to 150ms, which uses around 5% CPU.

    Assuming your results were using the 100ms delay, and that QuietMBP is the only application responsible for the loss in battery life, then with the switch to 150ms you would get about 2 hours 33 min, which would beat all other solutions. It would be good to test this in practice under the same conditions as above.

  13. Chris Says:

    On my new MBP with the newest firmware, MNK does not work at all, even after many attempts, as a previous user suggested. The only surefire method for me right now is QuietMBP. I like it because I have the choice of turning it off if I want a few extra minutes of battery- something that you have to reboot for if you’re using MNK.

  14. Sodpaz Says:

    I made this quick AppleScript that launches and closes Photobooth and then starts MagicNoiseKiller

  15. dar Says:

    It seems like windows xp installed under boot camp does not have the whine issue. The theory could be that it uses more power at idle then osx. Have you tried testing the battery life under xp? thanks

  16. RyanC Says:


    Great articles about the MBP whining problems. My own problems aren’t quite as bad as other people seem to be describing, which is good, but there are times where the noise does get louder and becomes irritating, most of the time though it is just background noise i don’t notice unless I listen for it.

    Anyway I thought I’d share my own experience. Basically the noise does definitely go away completely if I open up Photo Booth. The strange thing is, the weird screen inverter noise, which goes away only if the screen is set to full brightness, also goes away when Photo Booth is running – it doesn’t matter what brightness setting I use, if Photo Booth is open, both noises are completely gone!!!

    Just wondered what you make of that?

  17. grommit Says:

    Is MagicNoiseKiller working for anyone in 10.4.6 and could someone please advise me how to use this app correctly and whether it can be loaded on startup. Greatly appreciated. I am a mac noob.


  18. Angie Says:

    I got my MacBookPro a couple of weeks ago even after reading about the annoying noises and hearing a particularly loud online demonstration. I didn’t notice the noise at all for the first week. I only recently noticed that every time I took the power cord off, a significant “buzz” or “tiny grind” started. To any flutists out there, it reminds me of the overtone you hear when two flutes are harmonizing correctly.

    I read up on redsweater’s fixes and felt confident enough to give one a try.

    I liked QuietMBP’s slider, but after reading about the 11 minute battery life difference, I opened up MagicNoiseKiller. I have 10.4.6, 1.83 GHz, and 1 GB RAM, and MNK is working great. I can still notice a slight whirring noise when I unplug the power, but it is not half the volume of the original defect.

    Good work, Daniel!

  19. chris kearney Says:

    It would be interesting to start cataloging serial numbers. ie: I have such-and-such serial number, and I experience the following. Just a thought.

  20. Angie Says:

    serial # W86121EHVJ2

    1. CPU Whine: YES, when I unplugged the power it was obvious. However, I just started using Daniel”™s MagicNoise Killer and the whine is barely there. I use the photobooth trick and it’s gone, but I undo the photobooth trick and it’s back some.

    2. White Noise: YES, simply the left fan constantly working to keep my lap a bit cooler than I might be otherwise. No problem to me.

    3. Hot: YES.
    My MacBook doesn’t do the whine unless I have my power unplugged.

  21. Andrew Says:

    The mirror widget no longer works for me. It works while running, but when I turn it off, the whine reappears. Just started today . . . MNK never worked for me either . . . no idea what to do, guess i’ll leave mirror running, but that’s an ever crappier work around . . .

  22. Dora Says:

    mirror and MNK doesnt work for me too. 10.4.6 and all the other updates are installed. Only way looks like quite MBP now.

  23. archad Says:

    I don’t have a MBP heat or noise problem because I have delayed my new mac purchase until you fine geeks either fix it or Apple gets their butt into gear and sorts out the problem!

    It seems they have been spending more time trying to enslave the masses with the iPod revolution than attending to the needs of their loyal developer/designer customer base.

    I have really been waiting for the 17″, firewire 800 and dual layer burning! Does the 17 also have the heat and noise issues?

    If they don’t get it sorted soon I will be running OS X on a Sony or Dell!

  24. davide Says:

    Oh, I’m such an idiot. I have run Software Update and it has installed 10.4.6. Now I’m back again with the whining noise, stronger than ever, and the magic, magic, magic MagicNoiseKiller doesn’t work any more. I’m so desperate, how can Apple do such things to me? I’m using apple since 1986, when I was a kid, and I never felt betrayed in such a way…

    Is anyone working on updating MagicNoiseKiller to make is as magic as before under 10.4.6?

  25. HaroldC Says:

    Have you tried to time the battery with the mirror widget trick?

    Does the mirror widget keep running when you hide dashboard? I see the green light. but wonder how much of a drain it is. Currently only the mirror trick and QuietMBP work for me. I’ve got 10.4.6 so MNK doesn’t work for me.

    Thanks all!

  26. Peter Says:


    Do have the cpu whine and goes away at 160 in QuietMBP… haven’t testet battery og noisekiller yet… thinking of trying my luck and send it back in hope of a miracle, but then again this machine i all new so it seems the problems has gone anywhere else than away :(

  27. shaheen Says:

    Really annoying problem.

    Why apple did not give any offical solution.

    Why all the suffering.

Comments are Closed.

Follow the Conversation

Stay up-to-date by subscribing to the Comments RSS Feed for this entry.