What if only one light (the 4th from the back/5th from the front) stays on?

I have a MacBook Pro 9,2 (MacOs 10.9.5) and started having problems with the battery (the menu says "No Battery Available" and the profiler says "There was an error while gathering this information."). When I checked the battery indicator lights, only one is lit (solid, not flashing), the 4th light from the back (5th from the front). The computer works normally (although it seems a bit sluggish), but if I disconnect it from the external power, it goes straight to hibernation. The battery has never been tampered with before. I tried resetting the SCM many times (according to the recommendation), but I have no verification did anything and the problem still persists.

Any ideas?