AddOn Part 57Y4185-AA is a Lenovo compatible LI-ION 6-CELL 11.1V 5200mAh NOTEBOOK BATTERY for Lenovo portable computers. This higher-capacity 5200mAh 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 T420 T510 T520 SL400 SL500 W510 and W520 series of portable computers. Proline 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.