R3, 500, 600, 700, 800, 900 Series iRobot Roomba battery on sale.
Roomba 500, 600, 700 and 800 Series Li-ion 4400mAh/14.4V Plus.Parts Battery for iRobot
Replacement Battery for Roomba 500 600 700 Series APS Battery 555 595 620 630 650 660 790" - Walmart.com
Roomba 645 Battery
How to maximize your Roomba's battery life - CNET
Amazon.com: iRobot Roomba Authentic Replacement Parts - XLife Extended Life Battery - Compatible with Roomba 400 600 700 800 Series Robots : Home & Kitchen