I plugged it and it showed fully charged after only a few minutes. I hadn't used it in a while so I started to use it but it only ran for a couple of minutes and showed dead battery. Then I plugged it in intending to do a 72 hour charge. Now it plays the song and beeps four times continuously and the red service light is on. Is the battery completely dead and can't be charged or is the battery charger bad?

Vacuums - iRobot - 5800 Scooba Vacuum