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.
Upon re-reading my last post was less than clear. What I am saying is that the only variable in any of the given scenarios is Windows 7, which would seem to me to point to a Windows 7 issue of some kind. I'm not an engineer, but it really is just troubleshooting 101.
Third post in almost as many minutes here ...
I have a proposition, if anyone from Microsoft thinks it would be of value.
I'm willing to downgrade my laptop back to XP, and install a brand new factory battery. I would use the laptop for a set amount of time - say one week of normal usage, and then reinstall Windows 7 using the same battery and track usage for the same amount of time.
If the battery shows markedly different behavior, and in particular the kind of degradation that is being discussed on the blogs, would you agree that this points to an issue outside of the battery or the laptop charging hardware? Then at least we would have (1) legitimized the reported behavior, and (2) narrowed the cause of that behavior to the OS, correct?
Okay, so *you* set a threshold that isn't useful to me. How do I set a different threshold?
(I use a notebook for portability but am always near power, usually docked. Thus my battery is already down to 60% despite only going through about 30 cycles. I really don't care.)
Last Full Charge capacity is different than Total Capacity.
The Consider replacing your battery message validates that the Design Capacity is not equal to 0 or not equal to UNKNOWN_CAPACITY (-1). In neither case will the Consider replacing your battery message be shown.
Total Capacity can not be used for this warning as its value changes quickly at runtime as the battery is charged and discharged. We call Total Capacity "Remaining Capacity" and it is the value used to determine the % remaining and in conjunction with the rate of drain, the estimated time remaining.
The Last Full Charge capacity is a more static value that we expect to change slowly over time with each charge and discharge cycle.
the util called battcursor which someone mentioned in one of the comments above shows;
Total Capacity: 4,752 mW
Designed Capacity: 4,752 mW
Battery Capacity: 2,899 mW
(on charge atm)
Then does this mean that there prolly won't be any such battery issue on my laptop if it is upgraded? It is compaq presario c700 which i purchased about 1 and a half years ago and it was refurbished product (seller told only the box was opened and then refurbished though)
Based on Pat's message, if Total Capacity cannot be used, then there is a problem. When Windows reads Design Capacity at 0 or unknown, or some large value, 705004 (This is on a BRAND NEW battery by the way), and the last full charge capacity is 55451 (which is the REAL maximum the battery holds), then obviously the battery message will show. Microsoft needs to address this, since its a possible behaviour to have either 0, null, or some large value for Design Capacity. I can send screen shots if you really need proof. This battery is BRAND new. It is Less than one week old.
I can verify that when Designed Capacity is at unknown, the "Consider replacing your battery message still shows up".
I have this problem with a pretty new Compaq Presario. In my case, it appears to be caused by an intermittent power connection, or the fact that the error message and the intermittent power connection appeared at the same instant is a fantastic coincidence. I have fixed that problem, and I would expect this message to disappear. If the condition is magically fixed WITHOUT replacing the battery, will the error message go away? I presume so.
Well I have a Dell Latitude D820 that up until now never had a problem with it's battery. After using Win7 for a month it's displaying "Consider replacing your battery messages".
Seems to me like Win7 is detecting that the capacity of the battery has been exhausted when in actual fact it has not. Consequently the OS shuts down prematurely.
I updated the BIOS to the latest hoping it would fix the problem but there's been no change in behavior.
The message may be accurate, while still being annoying and in poor taste.
This sort of warning from Windows may have an "impending doom" taste in the worst case, or the "your machine sucks" flavor at best. Is my battery about to explode? Flake out at random? Probably. Why would the OS warn me? I already know that the battery is old and provides 40 min. of uptime.
If the battery holds a 1.5h charge instead of 2h, the user is unlikely to go out and order a $100 battery on a 3 year old laptop valued at $300. How sensitive is the feature?
The point is that the feature might be technically working fine, but still be a nag.
I think either DanLee81 / kev99sl is True. I dont think M$ can say it's not a Win 7 issue, as many people here itself say it happens in New battery/laptop and M$ coming out and saying they got just 30 cases. It means either M$ and their OEMs dont' want to take up this issue, which might become Toyota issue and Win 7 might face the same issue, which might doom M$. So, M$ come out clean of this issue.
Ok, now coming to the issue, my laptop is new as as kev99sl mentioned mine is also HP pav. 9500t, bought 2 yrs back, but battery got replaced, not just battery, HP replaced every part of this laptop within last 1 yr. So, here are my questions.
1) Why it didn't came in any of the Beta versions of Win 7 as I was using it before the release ver is installed
2) Why it's coming in a battery which's less than 1 yr old
Either Win 7 is draining battery or calculating it wrongly. In either case, it's still an issue with Win 7 and on M$ plate.
My wife and I both have the Lenovo X61.
I got the battery error message last week and my battery refused to charge. I tried everything to get it to work but it seemed like it was completely dead.
Then I took my wife's battery and swapped.
Once I powered up her Lenovo, my "dead" battery started charging.
It's been a few days now and my formerly dead battery is working fine on her Tablet PC.
The battery is old, 3 years but it's definitely not dead. This is a software problem with the OS, not the hardware.
There is a UI problem here too. The user only sees the conclusion: Your battery is bad. The user is
given no idea what that conclusion is based on, so the impression is simply "trust me".
I honestly think this new "feature" is really a nag. No one wants to see this. The best thing that could happen to Windows 7 is if Microsoft strips all of this new "feature" of the battery away, and just re-implemented the ACPI/Battery driver from Windows Vista verbatim. No changes. That would be the best case scenario. That way there is no room for error, espically when Microsoft doesn't want to actually find the root cause of the whole problem.