Activity Monitor Draining Battery

Occasionally, at seemingly random times, my battery starts to drain about a percent every minute or so. (This is unusually fast). When I look at the Battery icon on the task bar (at the top of the screen), the Apps Using Significant Energy lists HP Activity Monitor as a battery-intensive application. However, when I Splat-TAB, Activity Monitor doesn't show up. Additionally, when I click on the application icon, then Splat-Q, Activity monitor continues to run as it did before. When I try to force-quit Activity Monitor, nothing happens.

What's happening?

Why can't I quit Activity Monitor / how do I quit Activity Monitor?

What can I do (other than restarting my computer every time) to stop the battery drain?