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.
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Using Windows 7, no matter how many hours I charge my netbook, I get a message that says "84% available, plugged in, charging".
I can never get past an 84% charge. Is that Windows 7 telling me that although my battery has been charging forever, it now has just 84% of its original maximum charge?
If there are lots of people with subscribed to the Engineering 7 blog, it might be worth putting up a post to mention the new Engineering 8 blog at http://blogs.msdn.com/b/b8/ because lots of people that followed here would be interested to pick it up.
I've spent a fair amount of time trying to understand why my laptop suddenly went from almost 90 minutes of run time to fewer than 5.
What I found is that apparently Windows turns off the charge when "capacity" is greater than "last full charge". Mind you -- I don't have access to the Windows source code, so I'm just guessing.
What I do know is this -- turning off ACPI during the charging cycle has increased my capacity from about 7,000 mWh to almost 15,000 mWh and increased my battery run time from less than 5 minutes to almost 30. As I continue to cycle the battery with ACPI turned off during the charging cycle, I continue to recover capacity.
You can't determine your actual percentage of design / original charge capacity with the power meter. You have to run the command line tool (whose name I forget) to query the current capacity, then divide that by the actual original capacity. My system had been showing "100%" despite ACPI knowing that the battery had less than 20% of the original capacity left in working order. Using a technique I developed to recover capacity lost due to ACPI, I now have almost 35% of my original capacity and Windows will still show that as "100%" when all 35% of the original capacity is recharged.
The short and sweet answer is that the power meter lies.
I'm beginning to like your posts!
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mi bateria no registra cargado ni mide si cargo , pero cuando lo dejo en bateria me dura dos horas , pero no puedo indenyificar cuando se acaba la bateria porque no me avisa ayudenos creo que en windo 7 que no me edentifica si cargo o no . mi bateria esta biem , pero no me avisa.que ago.
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.<a href="http://easy-reisen.ch">last minute angebote</a>
This totally resonates with me and I had been falsely attributing the declining battery life to Factor X and not given it much further thought. I think it's bshite though that my battery is performing so poorly already after only 17 months. What the hell happened to companies constructing quality products. Hi-tech firms have gotten insanely RIDICULOUS with wanting to continuously force sales peddling their low-quality wares while my aunt's 15-year-old laptop is still going strong, back when Japanese was still synonymous with the everlasting utmost in quality, well worth a few extra quid. SHAME ON GATEWAY!!!
Two months ago the battery of my HP DV4 displayed the exact same message. I have been on Windows 7 since Jan 2010. I am currently in the process of buying a new battery.
Thank you for this article.
Sounds like a MS self-serving article. I started getting this message on mt ASUS, and trusting the message, got a new battery right away, The message stayed with the new battery. So not only am I faced with battery concerns, but have apparently spent money for nothing.
Please, I don't know English, ¿can you speak Spanish? Thanks.
lI install email@example.com So what type of battery and how do
really nice blog !
<h1>head up !</h1>
So how many extra Notebook / Laptop batteries did you buy (you are not alone) before learning that the firmware(BIOS)_BIF method must be used for power management to work on notebooks /laptops upgraded from Vista? Advanced Configuration and Power Interface (ACPI) See Article ID: KB981200 at support.microsoft.com/.../en-us, Tags: Power Management, Battery, Rip-off, Wasted Money, Irresponsible. The response came later but still many are buying multiple batteries to solve this problem and they need a bios upgrade to be published by the companies that made this notebook / laptop! Should not the companies be told about this so they can offer bios upgrades?