Replacement iRobot Roomba 551 Battery - High Capacity Battery for iRobot 80501 Robotic Vacuum Cleaner (3500mAh, 14.4V, NI-MH) Replacement iRobot Roomba 551 Battery Replacement for iRobot 80501 Robotic Vacuum Cleaner Battery Batteries One Year Warranty Capacity: 3500mAh, Upstart Battery Brand On Sale for a Limited Time!