Red flashing battery led after running the batteries empty

I did by mistake not plug in the power connection into the laptop, INSPIRON 510m, and after having started over the computer after battery - low warning it continued to run for a while and then went ded. However it started and was charging the batterie after plugging it in to the wall. But I have a flashing red battery-LED on the computer. Four fast red flahes and then a longer green and a short pause and then over and over again, red... green red... green! Does anyone know what it is and how to get rid of it?