When our 10 year old Roomba 500 series robot vacuum cleaner ran less than 10 minutes, I decided to buy a new battery for it and chose the updated Exmate Upgrade 4800 mAh 14.4 Ni-MH -Battery pack . So far this is a great solution! After installing a new battery and leaving it on the charger overnight, I pushed the start button and the old Roomba ran just fine for over half an hour before docking for a well-deserved rest. We are very happy with the new life this new battery has given our Roomba!