We are investigating this issue in conjunction with our hardware partners, which appears to be related to system firmware. We are working with our partners to determine the root cause and will update the forum with information and guidance as it becomes available -Microsoft
One of the key benefits that was supposed to be brought about by Windows 7 was an improvement in battery life said to be in the 20 percent range over notebooks running Windows Vista. “We’re achieving a very significant amount of battery savings,” Microsoft principal program manager Ruston Panabaker said at the time. Apparently, many Windows 7 users are not always finding that to be the case.
Geek.com noted that several laptop users on the TechNet forums are experiencing lower charging capacity and shortened battery lives once they upgraded to the new operating system. One frustrated TechNet Forum poster DanLee81 explains:
My battery is less than ONE year old, and now it only holds a charge for less than one hour. It used to be two hours on average battery life, but a couple weeks ago, Windows 7 decided that 28% battery life remaining = 0%. It went from 28% to 0% in the matter of minutes, then windows hibernated. Ever since then I can only charge to 72% battery and at that charge percentage, the battery will only last 30 min.
A spokesman from Microsoft states that it might be a problem in communication between the BIOS and Windows as that is where 7 gets all of its data on battery life. Whatever the case may be, If you receive a message that your battery is bad and you are a Windows 7 user, contact your PC manufacturer to determine if the message is an error or not.
As of now, there is no particular word on how Microsoft intends to go about fixing the Windows 7 battery issue.