Stay unplugged longer with the help of a spare or replacement thinkpad system battery get more the twice the capacity of the 4 cell system battery select models or carry an extra to extend your unplugged computing time its compatible design allows it to be in the system when the system is connected to thinkpad x200 ultrabase compatible with lenovo thinkpad x200 x200s x200si x201 x201i x201s features lithium ion li ion technology capacity 7800 mah 9 cell rechargeable system bat