The 6-cell ThinkPad battery 77+ is a replacement'spare battery for P50 system. The battery is rechargeable and can be used as replacement or as a convenient spare for mobile workstation ThinkPad P50 system. This battery is powered by Lithium-Ion technology and has a safeguard chip which authenticates with Lenovo systems. The battery lasts on average 90 watt hours* and utilises over-discharge protection to ensure a secure flow of power. *Many factors affect battery life. These include: screen brightness, battery conditioning, features, applications, power management and other customer preferences.Lithium-Ion (Li-Ion) technology 6 cell system battery Over-discharge protection to prolong the life of the battery Battery energy (Watt-hours): 90Wh Battery Safeguard chip authenticates with Lenovo systems