The 6-cell ThinkPad 76+ battery utilises Lithium-Ion technology and over-discharge protection to prolong system battery life. The rechargeable battery runs for approximately 48 watt hours* and is compatible with Lenovo E550 and E555 devices and those requiring ThinkPad battery 76+. Each battery is chipped to authenticate with Lenovo systems. *Battery life is affected by many factors. These include: screen brightness, power management, battery conditioning, features, applications and other customer preferences. ThinkPad Battery 76+ (6 cell): Lithium-ion technology 6 cell system battery Over-discharge protection to prolong the life of the battery Battery energy (Watt-hours): 48Wh Battery Safeguard chip authenticates with Lenovo systems