Macbook turns off without warning when battery gets low

When my macbook is not plugged in and I'm using it with only the battery, it will just turn off without warning when the battery gets low. The battery will be fully charged and I'll only be using it for about 15 mins and then it just turns off. This has been going on for over a year. Before I used to get that warning saying that it needs to be plugged in or whatever, but now it just turns off. Would this be a problem with my macbook or just the battery?

In addition, the "breathing" light in the right bottom corner of my computer hasn't been on in over 18 months, but my computer seems to be working ok (for the most part). I've tried searching for this problem on the internet but can't find anything about it. Has anyone heard of this before?

Thank you

Give this thread a read...only a couple of days old:

http://www.mac-forums.com/forums/apple-notebooks/165218-draining-battery-power-off.html

- Nick

been a member since 06 and you dont know about calibrating the battery, shame on you then again that battery could on its way out, hence not acting right.