I have an 15" AlBook, about 2.5 years old. Sometimes right after I unplug it, it gives me an almost out of battery notification, and shows a full battery on the display, but says it has 7 or 8 minutes left. Leaving it alone for five minutes or so makes it display almost 3 hours remaining (what I expect from a full charge). It did this for a few days about a month ago then stopped, but its acting up again. Is this a sign its about to die or just random weirdness? Thanks!