You are complicating something very simple ... and Windows 7 actually manages batteries just fine. I would suspect the battery itself before the OS .... but that's just me!
I own/operate a brick and mortar computer store, and I never run into these issues you are speaking of, and I probably see 50+ windows 7 laptops a month.
If you want a really decent battery management tool for Windows that is FREE (as in beer), then go to:
http://batterybarpro.com/ (free basic version at bottom middle)