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Microsoft Looking Into Windows 7 Battery Failures
Jared writes "Microsoft says it is investigating reports of notebooks with poor battery life with Windows 7, as first reported by users on Microsoft TechNet. These users claim their batteries were working just fine under Windows XP and/or Windows Vista, and others are saying that battery problems occur on their new Windows 7 PCs. Under Win7, certain machines spit out the following warning message: 'Consider replacing your battery. There is a problem with your battery, so your computer might shut down suddenly.' The warning is normally issued after using the computer's BIOS to determine whether a battery needs replacement, but in this case it appears the operating system and not the battery is the problem. These customers say their PC's battery life is noticeably lower, with some going as far as to say that it has become completely unusable after a few weeks. To make matters worse, others are reporting that downgrading to an earlier version of Windows doesn't fix the problem."
This is one of those things that's really hard to pin down.
LiON batteries -- what's used in most laptops and netbooks now -- have different kind of failures and limits from the older NiCD and so on. Aside from the catastrophic failures that made the news, what happens with LiON is that there are a limited number of charge cycles per cell no matter what you do. The cells generally go around 300 charge cycles before their capacity drops to about half. The controller in the batteries (which prevents them from just bursting in flames all the time) senses this and reports it back to the os.
The result is that when you upgrade the machine, you've already had it a long while and you're not far from that day when suddenly you notice your capacity has dropped to about half and you'd better replace the battery. Your cruising along at 60% then a minute later you're getting the warning that you're out of battery -- one or more cells is no good anymore.
To test this, you'd have to buy a new battery first and then compare life cycles.
btw: Lots of theories about how to make them last longer -- most of the actual experts say to try to keep it at around 40% if you're going to store it and not use it, otherwise just use the machine. The controller won't allow it to overcharge an they have no "memory" per se.
The problem with quotes on the internet, is that nobody bothers to check their veracity. -- Abraham Lincoln
Lithium Ion batteries do lose their maximum charge over time, that's a fact of physics. How much charge they lose depends on temperature and how much they're charged up.
http://www.batteryuniversity.com/parttwo-34.htm