Last week I wrote about reports that some Windows 7 users are experiencing anomalies with battery life, or at least how Windows 7 reports remaining battery life. The issue seemed worthy of exploring, but not big enough to cause any significant damage to Microsoft's flagship desktop operating system.
The official statement from Microsoft last week was:
"Microsoft has been made aware that some computers running Windows 7 receive a warning that the battery needs to be replaced when the battery is new or in good health. In conjunction with our hardware partners, we are investigating this issue. The warning received on some computers using Windows 7 uses firmware information (information about hardware status provided by the PC itself) to determine if battery replacement is needed. We are working with our partners to determine the root cause of what appear to be erroneous warnings and will update the TechNet forum with information and guidance as it becomes available.
The battery notification is new functionality in Windows 7, so the notification itself should not be an indication that customers are having this issue. Windows Vista and Windows XP did not display notifications when it was time to replace the battery. Customers who have already confirmed their battery is fine should contact Microsoft technical assistance for help."
Then, over the weekend I received a status update from a Microsoft source that asked to remain anonymous since the statement was unofficial:
"We've had 8 million pre-release testers on old hardware, 60 million PCs, and now this report of battery problems on old hardware is surfacing. This appears to be a very limited issue--aside from the discussion in the forum you noted in your story, we have yet to see any official reports or open tickets come in through tech support call centers. In testing on this issue the root cause appears to be actual battery performance or failure, which Windows 7 is reporting (via the notification), but not causing. So the notifications appear to be working as they were designed to do from what we're seeing. Microsoft has extensive testing, QA and support efforts and has multiple groups looking deeper at this issue, along with our OEM partners, to ensure that it is, in fact, the anomaly that it appears to be at present."
That update was followed with a similar declaration by Steven Sinofksy, president of the Windows Division for Microsoft, in a blog post on the Engineering Windows 7 blog:
"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. "
Sinofsky does more than simply deny responsibility or pass the buck, though. He provides an in-depth explanation of how the hardware, the battery, and the operating system work together to determine and report on the condition of the battery.
The crux of the problem may lie in simply misunderstanding an alert that is new to Windows 7. Sinofsky explains:
"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 percent degradation (that is the battery is performing at 40 percent 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 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." [emphasis from Sinofsky, not me]
So, to sum it up, the Windows 7 battery issue seems to boil down to Windows 7 correctly reporting that the battery is performing at less than 40 percent of its specified capacity, but alarming users who have been using Windows XP or Windows Vista and believed the battery to be functioning as designed.
Looked at from that perspective, it seems that Windows 7 is actually just doing its power management and battery life capacity reporting job too well, and that users who don't like the new warning message would prefer not to be reminded that the battery is slowly dying.