The 6-cell ThinkPad battery 77+ is a replacement/spare battery for P50 systems. The battery is rechargeable and can be used as a replacement or as a convenient spare for mobile workstation ThinkPad P50 systems. 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): 90 Wh Battery Safeguard chip authenticates with Lenovo systems