HP Pavilion ZX5180US Power Problem

I have a HP Pavilion ZX5180US notebook computer that started shuting down unexpectedly. I have updated the BIOS and uninstalled and reinstalled the power management drivers. Periodically, even though the power cord is connected the computer switchs to battery power, runs down the battery and then shuts down.

Is anyone else having a problem with the power cord. I have used another power cord, checked the voltage and there does not seem to be anything wrong with the power supply.

Also when I use the computerwith part of the bottom exposed the problem is less frequent. My daughter had similar problems and HP “fixed” the problem by installing a new motherboard for big $$$s.

Thank you for your insight.