The Lenovo ThinkPad Battery 68+ is compatible with W550, T440, T440s, L450, T450s, T450, T550, X250 and X240 systems. This 6 cell battery utilises Lithium-Ion technology and allows you to stay unplugged longer, providing the longest possible battery life. The battery can provide power for approximately 72 watt hours* and is rechargeable. A safe flow of power is ensured by the over-discharge protection, which prevents damage due to incorrect voltage. Each one is safeguarded with a chip that authenticates with Lenovo systems.