I got this solution from another CCM thread:
"For those of you having the problem of a HP laptop shutting off when you unplug the charger and your battery is fully charged, I can help you. There is nothing wrong with the laptop, battery, or computer, it is a power management setting. If you go to display properties, select the screen saver tab, then click the "power" button, in the power schemes field is a drop down window, click on it and select "Rixane Power Scheme", it is a power switching utility that quickly switches between AC and Battery when the power cable/charger is plugged in or unplugged while the laptop is on. If you have it set to "always on" it will shut off when you pull the power cord, even if the battery is charged. This will also happen on many non-HP laptops, if you don't have a HP laptop or there is not a "Rixane" option available, select the "Portable/Laptop" power scheme. Hope this helps!"