R3, 500, 600, 700, 800, 900 Series iRobot Roomba battery on sale.
Amazon.com: iRobot Roomba Authentic Replacement Parts - XLife Extended Life Battery - Compatible with Roomba 400 600 700 800 Series Robots : Home & Kitchen
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Replacement Battery For iRobot Roomba 500 Series 600 700 800 780 650 14.4V 5.0AH | eBay