Stay unplugged longer with these genuine Lenovo batteries. These rechargeable batteries use Lithium-Ion technology and can be used as replacement for aging system batteries or as a convenient spare battery. The ThinkPad Battery 57++ (9 cell) features: - Lithium-Ion (Li-Ion) technology - 9 cell system battery - Over-discharge protection to prolong the life of the battery - Battery energy (Watt-hours): 100Wh - Battery Safeguard chip authenticates with Lenovo systems