The 6 cell lithium ion 70 thinkpad battery from lenovo is a rechargeable lithium ion battery it can be used as a spare battery or replacement for aging batteries this battery is compatible with lenovo t4102030 t5102030 w5102030 and l series thinkpads features lithium ion technology 6 cell system battery 57 watthr battery energy rechargeable with the thinkpad external battery charger 40y7625