The 3-cell ThinkPad Battery 68 powers X240, X250, W550, L450, T450s, T450, T550, T440 and T440s systems for longer. The rechargeable battery lasts for approximately 23.5 watt hours and can be used with the T440, T440s and X240 systems. Each one utilises advanced Lithium-ion technology and over-discharge protection to prolong the life of the battery. The battery is safeguarded with a chip which authenticates with Lenovo systems. *Battery life is affected by a multitude of factors, including features, battery conditioning, power management, applications, screen brightness and other customer preferences.