Notes on comments.
Welcome to our blog dedicated to the engineering of Microsoft Windows 7
Over the past week we have seen a little bit of blogosphere activity regarding Windows 7 and batteries, specifically the new Windows 7 message “Considering replacing your battery”. Since this is related to the engineering of Windows 7 we’re going to use this blog to provide an update to people. As we have talked about many times, we have a relentless focus on the quality of Windows 7 and we take seriously any reports we receive that indicate a potential problem that could result in a significant failure of the OS. In a previous post we talked about the steps we take when we receive a bug report, in particular when we start to see several reports that appear to be the same. For the past week or so we have been diligently working through these steps and more to see if there is anything in Windows 7 we need to address regarding this issue. At this time we have no reason to believe there is any issue related to Windows 7 in this context.
Several press articles this past week have drawn attention to blog and forum postings by users claiming Windows 7 is warning them to “consider replacing your battery” in systems which appeared to be operating satisfactorily before upgrading to Windows 7. These articles described posts in the support forums indicating that Windows 7 is not just warning users of failing batteries – as we designed Windows 7 to do this – but also implying Windows 7 is falsely reporting this situation or even worse, causing these batteries to fail. To the very best of the collective ecosystem knowledge, Windows 7 is correctly warning batteries that are in fact failing and Windows 7 is neither incorrectly reporting on battery status nor in any way whatsoever causing batteries to reach this state. In every case we have been able to identify the battery being reported on was in fact in need of recommended replacement.
Using all the tools at our disposal including contacting customers reporting this issue on forums, customer service communications, partnerships with our PC makers, and of course the telemetry in Windows 7, we have been monitoring reports and discussions regarding this new feature, trying to separate reports of the designed behavior from those that might indicate an issue with Windows 7. In the latter cases we are trying to understand the scope of applicability and obtain hardware on which to reproduce a faulty behavior. To date all such steps indicate that we do have customers seeing reports of battery health issues and in all cases we have investigated Windows 7 has simply accurately detected a failing battery. Before I go into our status on this particular issue, we should review the details behind this new feature.
One of the most obvious components of PC battery life (the runtime you get on battery power) is the battery itself. PC batteries inherently degrade in their ability to hold a charge and provide power (as is the case for all rechargeable batteries). The cause of this is complex and includes irreversible changes in battery chemistry, and increased internal resistance among other things and those in turn are dependent on the design and manufacturing of the battery. This degradation translates into less battery life for the user over the life of the battery in the PC. Ultimately, batteries must be replaced to restore an acceptable battery life. A quick check of mainstream laptops will show that batteries usually have a warranty of 12 months, which is about the length of time when statistically we expect to see noticeable degradation (meaning that you start to notice the need to charge more frequently). Those of us that have owned the same laptop (or mobile phone, or music player, or anything else with rechargeable batteries) for a couple of years and taken it through regular charge cycles have no doubt “felt” the decline in battery life though we might have attributed to any number of factors since we did not have any information available to us otherwise.
Windows 7 makes use of a feature of modern laptop batteries which have circuitry and firmware that can report to Windows the overall health of the battery. This is reported in absolute terms as Watt-hours (W-hr) power capacity. Windows 7 then does a simple calculation to determine a percentage of degradation from the original 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. The Windows 7 the notification is a battery meter icon and notification with a message “Consider replacing your battery”. This notification is new to Windows 7 and not available in Windows Vista or Windows XP.
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. 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.
As mentioned, 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. Below we’ll talk about the data we have to support this point of view. It should stand to reason that some customers would be surprised to see this warning after upgrading a PC that was previously operating fine. 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.
This data would confirm our point of view that we are seeing nothing more than the normal course of battery degradation over time. The transparency provided in this new Windows 7 feature produced a notice that previously was not available to customers and did so shortly after upgrade. This is the root cause of the urgency with which we’ve seen postings, but does not change the reality of the condition of the battery. We have no confirmed cases of new machines with the as-purchased batteries.
As we always say with regards to any reports on the quality of Windows 7, we are going to continue to be diligent and use all the tools at our disposal to get to the bottom of a report that has the potential to require a code change we would distribute to customers. We are as certain as we can be that we have addressed the root cause and concerns of this report, but we will continue to monitor the situation. In particular, we will continue to have focused communication with our OEM partners as they monitor their customers and PCs over time.
Finally, if you believe you are receiving this error and your battery is new or believed to be in great shape we would encourage you to report this to us or your original PC maker. You are welcome to send me mail through the contact form on this page, use the TechNet forum, the Microsoft Answers forum, or visit support.microsoft.com where you can get additional information about how to contact Microsoft assisted support in your region.
I have the same type of problem with my HP nc4400, on which I have both Windows XP and Windows 7 installed: under Windows 7 the usable time during battery operation, i.e. the time I can actually operate my PC before Windows 7 shuts it down, is significantly less than under Windows XP. This isn't related to the battery or other hardware, it is definitely a Windows 7 issue.
In response to Charles Keledjian: "If there was a problem with Windows 7 consuming more battery this issue would happen with ALL windows 7 installs. Is this the case? No. Since it only happens to a few systems, then is hardware specific, and since no OS can do more than just read battery status, and battery operation is fully controlled by hardware and BIOS, then the logical conclusion is that Windows is not to blame. As simple as that."
Well, no .... What is clear is that it is an OS issue with certain hardware configurations, as the issue does not appear with other versions of Windows on the same hardware. So it is very far from "clear" that it is not an OS issue, and in fact quite the contrary: Everything points to the OS. The fact that the problem does not appear in XP or Vista also negates the notion that battery operation is "fully controlled by hardware and BIOS." I would also remind you that the OS can do plenty of things that may impact battery life beyond its "control" of the battery or charging functions, to wit: Run extraneous processes, fail to throttle the CPU, spin CPU cycles, read battery life incorrectly and shut down the system based on incorrect values, and myriad others. (This was an issue when Vista was first introduced, no? Again, on some systems in some configurations.) I'll only add that, in my case, the problem did not occur under the beta version of Windows 7, and only appeared with the Release Candidate, pointing yet again to something in the OS.
Further, it most certainly does not point to a BIOS issue, as the same old BIOS gets along just fine with the battery, again, in other versions of Windows. Further still, and more to the point, I do not recall the Windows 7 upgrade advisor pointing out the need to upgrade my old and tired BIOS in order for Windows 7 to run on my more-than-adequate hardware.
Again, troubleshooting 101.
Further to Charles Keledjian: Just to add that the *only* way I measure battery life is through usage, i.e., the amount of time I can spend on battery. In all tasks, under all scenarios, that usage has plummeted in Windows 7. Also, I've never run, nor had to run, any OEM software of any kind to control fan speed. (Never mind the fact that I am fully conscious of when, how often, and for how long my cooling fan is spinning as it is quite loud.) The first thing I do after purchasing a new computer is to completely wipe and reformat the drive and install a pristine copy of the OS, thus my XP install was fresh with extraneous "utilities" from the OEM. Same with my Windows 7 install.
Meant "without extraneous 'utilities'" in that previous post, not "with extraneous 'utilities'".
Running Asus 1000HE for 10 months now (Windows 7 beta, 7 RC and 7 RTM) and see no battery capacity change at all. Completely satisfied.
If you pay attention to the screenshot provided, you can see the poor wording already, the machine is plugged into AC power, but it's threatening that it will shut down suddenly even while plugged in.
I've experienced this myself, I've 'cleared' these messages by:
Unplugging and replugging the power, and rebooting after that.
Given the odd, inconsistent nature of battery technologies (from the AA to the smart laptop batteries) it's a road I don't think they should have gone down using the inconsistent manufacturer-set data (that could all be bullcrap in the first place)
Actually I find this report very accurate, I had the issue with Battery but Vista never reported and when I remove my AC adaptor, the machine will die. But now after switching to WIN7, I get the warning and Red cross icon in the system tray. Good job WIN7
All Those Values that reads from the batteries are responsabilty of the manufactors if they are not right call them and ask them for a battery with the right values! also check on device manager if the driver fro the acpi is not missing... i notice mainly on x64 versions that somethims is hard to get the right drivers for the acpi! even when sometimes you try to install the driver from vista x64 it install but doesnt work, check for unknown devices on device manager!
You kids with the tinfoil hats are absolute dumbasses. Windows, let alone any OS cannot write to the battery, it just reports info from the BIOS. Dipshits.
Funny how some people tend to think their hardware is never at fault and that it is always Windows having issues.
You'd be surprised how many bad drivers and faulty hardware parts are out there with users not noticing anything except random crashes in the OS. In this case it being either just old batteries or bad ACPI fields.
I applaud the action and stance Microsoft has taken with this issue. While the pre-Windows 7 Microsoft probably would have taken the same measures internally, it wouldn't have responded publicly like this.
More of the same! (Like IE9, VS2010, Office 2010!)
@ MacGyver: Exactly. Microsoft is being very proactive in offering to look into it with customers, but the bottom line is each of these issues is likely a driver or BIOS issue. Windows can only do what it is told. If the ACPI driver and BIOS are reporting bad information, then what is Windows to do?
Sadly, many laptops require custom ACPI drivers and software to work properly. Upgrade Advisor can't possibly check all of this for every model, but it certainly does for a lot of them. That's why it's important to select OEMs that don't discontinute drivers immediately after selling the last model and why I prefer those that don't require custom drivers. Look for those that go for certification, etc. too. I won't mention vendor names, but I had a bad experience with one manufacturer that required custom GPU drivers but never updated them after the units stopped shipping. Using generic drivers resulted in lost functionality and blue screens, which wasn't worth it. I'll never buy from them again.
Funny. When someone asks me why i *like* Windows 7 (over Visa) the first thing i say is that my laptop's battery life is 2 times or 3 times longer now! It's an HP Pavilion tx1417cl notebook btw. One of those notebooks with a swivel screen that becomes a tablet.
No, for the pedantic, i do not know the "battery life" per say, but you knew what i meant. A full battery charge last 2 or 3 times longer for me and my laptop with Win 7 than it did with vista.
It's over a year old, no warning yet to change it. Fingers crossed. J.
I'm curious after reading your posts at your laptop's behavior. Perhaps you should consider eliminating Windows from the equation by downloading a live CD of your favorite linux distro and doing some troubleshooting.
I suggest dumping your ACPI tables before and after you plug the laptop into the wall, and comparing them to what utilities in Windows are reporting.
If there are wide discrepancies between Linux and Windows, I'd continue to blame Windows. But if both are having problems, it sounds like your laptop or battery manufacturer dropped the ball.
Here's a quick description of how to extract and parse the ACPI tables on Linux.
If your battery life is poorer under Windows 7, make sure you have the latest BIOS and driver updates from your manufacturer.
My Sony Vaio exhibits relatively poor (1-3 hours instead of 4-5) under both Vista and Windows 7 if the Sony drivers and utilities are not installed.
This isn't necessarily a problem, it's just reality... If you don't like it, complain to the hardware vendors who tie power management functions to custom drivers and utilities.
In my case, going from the stock manufacturer-provided Vista install to a clean Windows 7 install resulted in significantly reduced battery life UNTIL I installed those drivers. After installing them, Win7 battery life is significantly *better* than what I experienced with Vista.
I have not found any problems on the laptops I use..
However as I posted on Windows7News when this problem was first reported I have identified battery manufacturer "Simpli" came with a dell 1501 and an acer netbook.. Both failed within a year.. I suggest avoiding this manufacturer if possible.. This problem was regardless of cells being used..
The Li-ion batteries shipping with computers today suck.. Many don't last even a year when installed 24\7.. If your computer is plugged in a lot then simply remove the battery..
As always to remedy the li-ion degradation run your battery bios recalibration (if your computer supports it).. You will notice even after calibration (and if battery is not brand new) that your battery actually has a lower capacity value now..
Windows as I suspected (and the above article supports) simply can't be the cause of peoples batteries failing..