The Windows 7 battery life issue: What's making notebook batteries die?

Since Windows 7's final release last fall, some testers have been reporting that dual-boot network computers seem to consume power more efficiently running Windows XP than Windows 7. One example came last October from JKOnTheRun's Kevin C. Tofel, who saw his own Toshiba notebook battery die 45 minutes sooner running Win7 than Windows XP. But even then, Tofel was skeptical of a few curious facts, including that Toshiba changed its power management utilities.

Since 1999, the system that has reported battery capacity and relative power levels to the operating system has been the Advanced Configuration and Power Interface (ACPI), developed by industry leaders such as Intel, Phoenix Technologies, and Toshiba. But ACPI was developed with the BIOS in mind; and as PC architecture evolves, as even Phoenix will readily concede, the conventional BIOS is becoming an historical remnant. And history has also shown that as a lithium-ion battery degrades, its capability to report its own health degrades with it. Only now have batteries become capable of reporting their capacity -- how much charge they can hold -- as compared to their manufacturers' specifications.

Recently, some Windows 7 users have become acquainted with a new "feature" of the operating system -- an advisory where the operating system suggests it might be time for users to replace their batteries. That started feeding into reports that Windows 7 was degrading batteries faster than its predecessors, such as this from InformationWeek that cites members of Microsoft's support forums. That helped feed stories that the operating system was "tarnished" by a battery plague.


The instigator of these complaints appears to be the advisory itself, which users may be interpreting as an indicator that Windows 7 has "eaten" their battery. In fact, as Microsoft Windows division president Steven Sinofsky told users today in a post to the Engineering Windows 7 blog, Win7 is merely reporting a fact of everyday life, whose information had not yet been standardized in the days of Vista.

"PC batteries expose information about battery capacity and health through the system firmware (or BIOS). There is a detailed specification for the firmware interface (ACPI), but at the most basic level, the hardware platform and firmware provide a number of read-only fields that describe the battery and its status," Sinofsky writes. "The firmware provides information on the battery including manufacturer, serial number, design capacity and last full charge capacity. The last two pieces of information -- design capacity and last full charge capacity -- are the information Windows 7 uses to determine how much the battery has naturally degraded. This information is read-only and there is no way for Windows 7 or any other OS to write, set, or configure battery status information. In fact all of the battery actions of charging and discharging are completely controlled by the battery hardware. Windows only reports the battery information it reads from the system firmware. Some reports erroneously claimed Windows was modifying this information, which is definitely not possible...Every single indication we have regarding the reports we've seen are simply Windows 7 reporting the state of the battery using this new feature and we're simply seeing batteries that are not performing above the designated threshold."

As Sinofsky explains, batteries can report their capacity using ACPI in terms of Watt-hours (W-Hr); and from now on, Windows compares this capacity against design capacity. "In Windows 7 we set a threshold of 60% degradation (that is the battery is performing at 40% of its designed capacity) and in reading this Windows 7 reports the status to you. At this point, for example, a battery that originally delivered 5 hours of charge now delivers, on average, approximately 2 hours of charge."

That's a fairly simple calculation to perform, and theoretically, it's been there since the turn of the previous decade. But it would appear that the readings reported by batteries may only have become reliable enough for Windows to rely on this conclusion, in only the last few years.

Last July, Microsoft published this document for hardware engineers explaining how Windows 7 polls information from new-generation batteries. Although Microsoft explains that Win7 can only read information from these batteries, it clearly advises engineers that it's up to them to set their batteries' firmware so that it reports the proper levels.

As the document reads: "Users who run their system on battery power sometimes use the system until the battery is critically low and must enter the hibernate state to save open programs and data. Windows provides multiple battery warning level and action policies that the system manufacturer can tailor to the underlying hardware platform and battery capacity."

The four settings that the document states may be customized by engineers are low battery level, reserve battery level, critical battery level, and critical battery action. These are threshold values separate from the real-time indications reported by ACPI, like last full charge.

With Windows 7, Microsoft introduced a completely revised power configuration utility -- a new PowerCfg, whose purpose is to enable engineers to determine the energy efficiency of a notebook computer. Just last month, Microsoft published a document explaining how the revised utility works:

"PowerCfg inspects the battery information during the analysis. It logs an information item that contains the battery manufacturer, the battery chemistry, the design capacity, and the last full charge capacity. PowerCfg logs an error if it cannot retrieve the battery information from the firmware. PowerCfg logs a warning if the last full charge capacity is less than 50 percent of the battery's design capacity. PowerCfg logs an error if the last full charge capacity is less than 40 percent of the battery's design capacity."

There's where engineers are given that 40% threshold mark for the first time -- the 40% mark that Sinofsky referred to in his blog post today. So the fact that users are seeing "Replace Your Battery" reports for the first time now, may only be because the reliability of such a warning has only recently become viable.

"It should stand to reason that some customers would be surprised to see this warning after upgrading a PC that was previously operating fine," writes Sinofsky. "Essentially the battery was degrading but it was not evident to the customer until Windows 7 made this information available. We recognize that this has the appearance of Windows 7 'causing' the change in performance, but in reality all Windows 7 did was report what was already the case."

30 Responses to The Windows 7 battery life issue: What's making notebook batteries die?

  1. beagle197 says:

    What a load of marketing crap and convoluted mumbo jumbo. Do they really believe everyone is so ignorant? How about they explain that their new OS requires the transistors to switch more frequently due to higher CPU loading from borked logic. That would go further to explaining why the batteries are always dead.

    • thinkaboutit says:

      Where did you get your electrical engineering degree??? switching of transistors or SCR's etc...actually reduce heat...heat is who is ignorant now.....beagle brain.

      • beagle197 says:

        I can see basic physics concepts can not reach your higher level brain functions. Let me explain it like this, the larger the % of time that the semiconductor device spends in transition, the more heat it will generate. Go back to circuits and electronics 101, monkey brain. No doubt Microsoft has produced another fundamentally broken operating system, thanks to their commitment to management incompetence over quality engineering. You are obviously part of the problem, and not the solution.

      • rtwnt says:

        Well let's see- we have reference Monkey brains and Beagle brains. For myself, I would prefer the designation of "drunken skunk" brain:)

  2. bigsexy022870 says:

    I have windows 7 on 2 latops. Have not had this issue or any other. The artcle is very well done. Finally some logical answers to serious questions.

  3. UsmanKhan says:

    Finally some logical facts in this article.

  4. Briantist says:

    Q. What's making notebook batteries die?

    A. Chemistry

  5. tomswift2 says:

    I believe a more careful reading of blogosphere presence will very quickly show that there is one very clear behavior being reported, and one supposition: Microsoft's responses to date have chosen to focus on the supposition rather than the actual behavior being reported.

    The *behavior* - which I assure you is easily reproduced - has nothing to do with the "new" or "not new" status of the battery. Rather, it has to do with a marked difference between relative battery life when running Windows 7 vs. any other recent variety of Windows (XP or Vista). Specifically, one's battery - regardless of how "healthy" or "unhealthy" Windows 7 deems it to be - goes from providing, for example, 1 hour of off-AC computing power, to some drastically reduced amount of time - say 20 minutes, all within a few weeks of installing the new OS. Further, this behavior is repeatable using a newly purchased battery. In other words, at some point, Microsoft and its OEM partners are going to have to conclude that a random sampling of consumers are somehow experiencing the extraordinary bad luck of constantly purchasing faulty batteries or, more likely, that there is an issue. I think it's simply a matter of time until the latter is uncovered, as the majority of impacted consumers are just now coming around to working through battery warranty issues, purchasing new batteries, returning new batteries assumed to be faulty, etc. only to discover that second and third newly purchased batteries do not rectify the problem. As you acknowledged in your message, the majority of these cases are handled through OEM support, or simply through people assuming the OS is correct and the battery is faulty, and therefore purchasing new equipment. Again, in time, the problem will become more and more self-evident to everyone, including Microsoft.

    Finally, the *supposition* which Microsoft is choosing to focus its public responses on is that the OS is somehow physically destroying batteries. I would suggest ignoring this supposition until the nature of the supposed problem is identified. To that end, I can provide Microsoft with an excellent and reliable way to verify the issue: Find several HP Pavilion dv9000t notebooks, with Intel processors, and purchase new batteries for each. Install and run Windows XP 32-bit on all of the notebooks, and install new identical batteries in each. Run each notebook/battery combination through the factory recommended charge/discharge cycles. Next, clean-install Windows 7 64-bit on half of the machines, and continue running Windows XP 32-bit on the other half. Use all of the notebooks in typical charge/discharge conditions for identical tasks for a month or so under the "Performance" power setting. I assure you that the problem will make itself evident very quickly, and that all of the Windows 7 batteries will exhibit marked wear and lower on-battery time vs. the XP machines.

    • rtwnt says:

      You provide an interesting test. My question is are you basing your supposition on the PowerCfg warning or on actually testing of the batteries. The reason I ask is that you say."Specifically, one's battery - regardless of how "healthy" or "unhealthy" Windows 7 deems it to be - goes from providing, for example, 1 hour of off-AC computing power, to some drastically reduced amount of time - say 20 minutes, all within a few weeks of installing the new OS."
      Now if you follow the blog, it says a 40% mark has been used. 40% of 1 hour is 24 minutes which is close to what you say.
      Since as the person below says, all batteries degrade over time and depending on how someone has configure the power consumption, even in an off state the battery would still use power.
      So, in my limited perspective it seems to be more of a problem with new info being given to the user and a high % set for this info to be given than any specific issue with Win7.
      Now one problem that I do see is this: "PowerCfg logs an error if the last full charge capacity is less than 40 percent of the battery's design capacity." Notice that this tells you that your battery may need to be re-charge not that you have to make funeral plans; however, the problem comes up in the message part: ""Replace Your Battery"" when what may only be needed is a re-charge.
      I admit I might be missing something so I would welcome opinions on this so that I can better understand this specific issue.

  6. chandler says:

    This is a informative article but it doesn't really address the core issue: battery drain is an issue on Windows 7. There are some people experiencing the annoying yet harmless battery notifications with older batteries that you discussed. However there are many others who have a serious battery life issue since installing Windows 7. I created a dual boot on my 6 months old Sony laptop with a fresh installation of Windows 7. When running Windows 7, my battery drains in less than 25 minutes but yet it takes over 1.5 hrs to drain in Vista. This is issue that many people are having with both fresh & upgrade installs across several brands of computers. There are several long threads on Microsoft Technet and other Windows forums about this issue. Microsoft is so far denying this is OS issue but I beg to differ.

  7. lileoj says:

    My wife's Windows 7 laptop with an 18inch display is just fine for battery life unless you play a DVD which is also processor intensive. I get plenty of battery life in it.

  8. techno_bob says:

    Well this explains why Win7 was giving me the "replace the battery" message while using it on a new Macbook with Parallels running in a VM.

    • PC_Tool says:


      Running Win7 in a VM... Dude, it ain't 7 causing that problem. Virtualization is notorious for wonking out the battery notifications...*none* of them pass ACPI information to the VM properly (At least, that I have found).

      I have the same issue in an XP VM...on my desktop. tells me thebettery is low. Cute, ain't it?

      Never trust a VM.

      Now, if it were to do this on a bare-metal install on your MacBook....

      • rtwnt says:

        What you say makes since on the VM issue but since I don't use VM, I can't really address the issue so I would be interested in knowing what it is about VM that causes the problem.
        Is it possible that in Win7, Running XP VM takes you a step back in time and not make available the info tool built into Win7? Would be interested in yours or anyone's input as this is one area I would like to experiment with in the future.

      • PC_Tool says:

        "so I would be interested in knowing what it is about VM that causes the problem. "

        Don't have the technical details or knowledge to competently answer this one, but I'll take a stab regardless (it's never stopped me before, so why now, right?)

        As I understand it, the guest-OS isn't really running on your system...insofar as "your system" is the bare-metal hardware your host-OS is running on. The VM virtualizes everything...meaning it's not directly accessing any of the actual hardware, and the Virtual hardware is all but generic....even with the "tools" installed.

        My guess is that "generic" hardware simply doesn't have the ability to properly handle such data for all the varying types of "real" hardware it gets it's input from. It may get it right on the majority of hardware, but it can't get them all... Kind of like how not all OSes support all hardware. The amount of effort required to code for all the variances simply doesn't pay off.

      • rtwnt says:

        Thanks PC_Tool. You give me a start in understanding this issue.

    • rtwnt says:

      Don't agree. This problem has nothing to do with Win7 or an Apple OS. The problem seems to be that information locked in the BIOS is not being given to the user or in a meaningful way. All Win7 does is let the user know information. Doing that would in no way cause a degradation in battery life. Now one may quibble on what % this info. is given but PowerCfg seems to be nothing more than a system info. tool and a beneficial one and the info given to the user can't help but benefit the user unless Apple or MS laptops prevent the user from exchanging batteries on their own

      • DrTeeth says:

        Losts of modern BIOSs are rubbish. They are just competant to boot Windows...the writers no longer care or have to.

  9. kenjunior says:

    Power settings plays a huge part in battery life. Just like a 100 watt light bulb consumes more energy than a 60 watt bulb. Win 7 perhaps does consume more power, ie pushing video cards harder with Aero, pushing HDDs for a couple more reads and writes, bumping CPU frequency up a moment longer. All turns into a heavier load on the battery.

  10. dracodos says:

    I saw this new indicator about 3 months back. My current laptop, an acer extensa, was bought used about 1 year ago, the manufacturer date was about 2 years back and I have no idea how the previous owner "rode" it before I got it. Considering i have that puppy hooked up a power cord 90% of the time while it's in use at work and at home i can only deduce why the battery decided to go ;) Funny thing is i already figured the battery life was getting short even before that indicator started. Already bought a new battery so i guess we'll see if i get the same things a year or 2 from now :)

    • DrTeeth says:

      The worst thing you can do for a battery is to leave it connected to the carger when it is fully charged.

  11. ghostface147 says:

    Windows 7 has reported no issues with any laptop that I have used. We all know that chemistry forces battery life to degrade over time. I have no doubt that some people are having issues with batteries quickly dying,. I have used Toshiba, Dell, and Lenovo laptops with no issues. One person above mentioned using an HP machine for testing. I believe that the issues with the problem laptops are isolated in so far that something else on that machine is contributing to the battery drain. Maybe some programs on certain machines need updating or some possible firmware update. I know Microsoft touts better battery life for all new OS' coming out from them, but I refuse to believe that a more intensive OS like Vista or 7 will markedly improve battery life if the chemistry behind the battery hasn't improved in several years. In other words, if people were thinking to get another hour out of a battery after upgrading to 7, they are mistaken.

  12. Registered says:

    in my humble opinion, battery technology can't keep up with current hardware power requirements,
    computer components are advancing far to quickly in the laptop market,

    considering that we currently live in a world that is definitely waking up to the concept of efficiency, the laptop market (or companies) still has not embraced this, it is appalling that the average battery life in laptops is lasting only 1.5 to 2.5 hours, I'm seeing dual core & now quad core laptops with high class graphics technologies being sold, I find this unbelievable,

    batteries are being strained to the limit, even to the point of melting (many cases over the last 10 years have been reported, along with power-packs) and yet laptop manufacturers are still trying to make faster more advance systems, why is the market trying to create PC inside a laptop, a power PC needs 550W PSU minimum, there is never going to be a solution to pumping that much power through a laptop in any of our lifetimes, these manufacturers should be finding ways of reducing the strain and increasing reliability, because laptop reliability on today's laptops are a joke,

    remember the old laptop's, you know the ones, the small 512Mhz 128MB 20GB hard drive notebooks,
    they were crap, the batteries lasted only 10months, but the laptop itself was still going 6 years later, man they sure new how to make laptops last back then, and they never over heated in them days,

    i think it's a joke how laptops of today are running out of battery power quicker than laptops of yesterday and the heat being generated from of lot of laptops these days, some of them can't even sit on one's lap because of 3rd degree burns.
    ...... quad core cpu's in a laptop....... how pathetic,

    Laptops are to advance,
    to power hungry,
    extremely running a hot temperatures,
    and very poor reliability, (insurance is NOW mandatory)

    • tontito says:

      They are reporting the problem using same hardware and different OS.
      It seems clear 7 seems to use more resources then XP. I have tested my self.

      I think we need something like vlite to start removing crap from 7...

      • AzureSky says:

        windows 7 uses your system resources more efficiently then xp ever did or in fact could, Rather then your ram going to waste just sitting there 7 uses it to cache files and apps you use alot, this has no negative effect on overall perf even if you dont do the same things over and over, because it can just dump whats been cached and free up memory for whatever application needs it.

        XP was a step down from 2k imho, Its less reliable, slower and has ALOT more bugs(even after the last sp and round of updates) 2k3 was what xp should have been but still, none of them make as good a use of system resources as 7 currently does.

        theres really not alot of "Crap" as you put it in a base 7 install, WMP/WMC maby, but you can remove that after install easy enough.........

  13. shallot says:

    People have a problem either way. Batteries always fail and till Windows 7 people were that Windows 7 is intelligent enough to tell people to replace the battery, people suspect Windows 7 rather than the battery....

    I pity MS, damn if it works, damn if it doesn't.

  14. morrig says:

    I only have a desktop,but on a wimpy single core,512 ram,it runs Win7 far better than XP.Boots much faster ,runs everything faster,so this shows(to me) that this O/S is much more efficient,and pro rata so should battery life be longer?

  15. Registered says:

    I have never owned a laptop, and I'm quite sure that the experience I have accumulated over the years by itself qualifies as ("Research")
    I'm a user support technician, I have set up many systems, and have seen many laptops over the years,

    power laptops are very expensive, and overall have poor reliability,
    such investments deserve peace of mind, and I have seen for quite some time now, that laptop reliability in general has definitely diminished to a point that insurance is mandatory, and i believe that laptop reliability is being sacrificed because laptops are being pushed to equal there PC counterparts in performance, there has to be a trade off, ATX systems have so much space available for components,
    laptops have very limited space, and yet performing as good as there older cousins.....

    and as for the insurance, here in England, over the last several years, laptop repair prices have been growing steadily and constantly,
    just for an assessment of a laptop is about £55, due to the growing complexities of modern day laptops, repair fees can cost unto 40% of the total cost of the laptop, sometimes even more.....
    imagine paying £600 for a laptop, and getting a repair bill of £250 for a simple component replacement.... then looking at the invoice and finding out that the component only cost £99, the rest was service charge!!!!

    for the record..... I don't do laptop repairs...... far to much hassle, there's usually about 20 screws to undo, and laptops usually have to be dissemble just in the right order,

    and as for taking care of laptops, you missed the point entirely i was making, granted treating a laptop with repect is a good thing,
    however, poor manufacturing, design flaws, and components being pushed beyond there capabilities all lead to reliability problems. and nothing the user does will change that fact of truth.
    if the laptop is built or designed poorly, then it's gonna break..... and interestingly on many occasions I have seen laptops needing repairing just after there 12month warranty has expired......LOL

    the truth is, the laptop market has gone the same way as mobiles, too many and too quickly are being created, mass scale production on multiple lines is very expensive, corners have to be cut.

    I'm just not seeing any innovations being designed specifically for the laptop computers,
    laptop systems feel to much like there older PC counterparts,

    it would be nice to see some breakthrough technologies for the laptop systems that target efficiency and power reductions, CPU-M processors being a good example,

    • deepblue says:

      @Registered: You must be the only person who thinks the same way I do about that! Computers are (on average) so much faster than I need for Linux, and I've had two cameras and a netbook die at 13 months on a 1 year warranty.

      The laptop I'm using right now has a Pentium dual-core CPU, 3GB RAM, and 250 GB hard drive. Necessary for what I do? Fat chance. It gets about 2.5 hours battery life, weighs way too much, and just feels generally cheap. I want a solidly built, lightweight laptop with at least 5 hours battery life. Tradeoffs? Sure. I wouldn't mind a Via Nano CPU, 512MB RAM, and 16GB SSD. Heck, Compiz might not like less than that, but Fedora 12's LXDE spin (what I use) will run well enough on a Via C3 w/ 128 RAM & a 4G SSD. It's almost laughable how little of my computer's capability I actually use...

  16. AzureSky says:

    or sniffing other dogs arses.....

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