RE: HP Pavillion DV6500 question
Is that 15 minutes of being actively used, or 15 minutes of sitting idle? If the latter, Windows 7 out of the box defaults to going into sleep mode around that time. There should be some indication of that, such as the power light briefly blinking every few seconds.
You should see what the battery charge level is after you turn it back on. If the battery is low, it is obviously a bad battery, if not and it can run another 15 minutes on the same battery without charging, then it obviously isn't.
As for the ticking sound, does it sound more like it comes from a speaker or more like a mechanical issue?