Morpilot 3800mAh Ni-MH Battery for iRobot Roomba R3 500, 600, 700 & 800 900 Series (Free Prime Shipping) $15.98
Morpilot via Amazon[amazon.com] has the Morpilot 3800mAh Ni-MH Battery for iRobot Roomba R3 500, 600, 700 & 800 900 Series on sale for $15.98 when using coupon code 6LWHG9ZS during checkout. Shipping is free with Amazon Prime.
[2017 Upgraded] High Capacity: 3800mAh / Battery Type:Nickel Metal Hydrate (NiMH) / Voltage:14.4V. It runs well for 1.5 to 3 hours per charge.
This battery is produced by the original iRobot manufacturer, and it is fully compatible with iRobot Roomba 500&600&700&800 series cleaner perfectly.