Dell Latitude E6510 battery issues

until today battery working very well. yesterday i notebook normally used with battery. when I came to the room today, battery symbol on notebook blinking orange fast. i had no problems with the battery before and working several hours.

i can not find what means the blinking led on battery. one click blinking every second led. when i push button and hold him, after blinking all lights up for a while. what this mean and why did it happen?