AddOn's 40Y8318-AA is a Lenovo compatible LI-ION 8-CELL 14.4V 4400 mAh Notebook Battery for Lenovo portable computers. This higher-capacity 4400 mAh battery packs more punch than the OEM. It has a similar form factor to the OEM and is made specifically for the Lenovo series of portable computers. AddOn batteries are 100% tested and compatible for the systems intended for. Battery life depends on many factors including: available DRAM, screen brightness, applications, features, power management, battery condition and other customer preferences. AddOn part numbers mimic the OEM, and are comparable in form factor and battery life.