In the past few weeks, my macbook shuts down when the battery dies. The battery does not even die at 0%, sometimes it shuts down at 5% or 10% remaining. I tried calibrating the baterry following this website: http://support.apple.com/kb/HT1490. But it does not really help. I regularly use battery in my macbook, I'd say I use around 2-3 cycles a week.

My charge cycles is 440 cycles, and my current battery capacity is 3400mAh from the original 4100mAh. I have 2008 unibody Macbook. Does anyone know how to make it goes to sleep before the battery's dead?

EDIT:

The OS seems the think that the battery is ok...