Windows 7: Windows 7 Battery Notification Messages - MSDN Blogs

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.

Microsoft investigating battery problems

The following data points contributed to our understanding of the reports we are seeing. Please keep in mind that all the telemetry we see is opt-in, anonymous, and respects our privacy policy.

• We have seen no reproducible reports of this notification on new hardware or newly purchased PCs. While we’ve seen the reports of new PCs receiving this notification, in all cases we have established that the battery was in a degraded state.
• Our OEM partners have utilized their telemetry (call center, support forums, etc.) and have let us know that they are seeing no activity beyond what they expect. It is worth noting that PC manufacturers work through battery issues with customers and have a clear view of what is to be expected both in general and with respect to specific models, timelines, and batteries.
• We’ve gone through all the major online support and self-help forums and when appropriate have worked to follow up with any reports of this notification being presented in error. Through this we have identified no reproducible cases where the battery or PC was new and have only learned of batteries that were degraded in capacity.
• In our telemetry from RTM code customers, only a very small percentage of users are receiving the “Consider replacing your battery” notification, and as expected, we are seeing systems older than ~1.5 years. We’re seeing relatively fewer notifications compared to pre-release software as the average age of the system decreases.
• Microsoft has received 12 customer service incidents in addition to pulling 8 additional incidents from various forums. To date (for a total of 20 incidents), none of these have shown anything other than degraded batteries.
• Microsoft has been using the technet community moderators to assist in further contacting customers reporting on this notification and we’ve assigned additional customer service personnel to be ready. However, of the 30 or so contacts we have received we have not learned of any new facts or conditions with respect to this notice.
• During pre-release testing of Windows 7 we saw almost precisely this same experience with customers in terms of the display of the notification. In fact, in looking at the hardware distribution of pre-release testing we saw an ever so slightly higher number of systems receiving this notice. This follows from the fact that a large set of customers are buying Windows 7 with new PCs or using the upgrade provided with a recent Windows Vista PC.
• When looking at the telemetry reports for the machines that have reported displaying this notification we have seen nothing in additional reliability data that indicates any other system anomalies.
• While the information regarding battery status is provided read-only to the operating system through ACPI, we performed a thorough code-review and verified that there exists no code that is capable of modifying battery status information.