The HP 620, 625 Probook, 4320s, 4525s & 4520s Primary Battery Pack is a 6-cell, rechargeable, Lithium Ion battery designed to work with various HP series portable computers. Take your office on the road without sacrificing performance, productivity or convenience with HP Notebook battery packs. Battery power gives you the ability to use your computer around the house, on campus, in the office, and when you travel either on business trips or vacation. Enhanced battery life helps you stay connected and be productive wherever your work takes you. Used as either a spare or replacement battery, this battery pack meets or exceeds the specifications of the original battery that came with your notebook. It interfaces with the HP Power Saver Utility on the notebook which features a charge indicator to help you monitor the available power.