AddOn Part #57Y4545-AA is a Lenovo compatible LI-ION 9-CELL 11.1V 8400mAh NOTEBOOK BATTERY for Lenovo portable computers. This higher-capacity 8400mAh battery packs more punch than the OEM. It has a similar form factor to the OEM and is made specifically for the Lenovo ThinkPad T410, T410i, T510, T510i, W510, and W520 notebook 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.