Have a second ThinkPad battery charged and ready to go whenever you need it. The ThinkPad External Battery Charger gives you maximum power flexibility by charging a spare battery independent of your ThinkPad system.

External unit operates independent of your ThinkPad notebook so you can charge a spare battery at any time.
Must be used with the ThinkPad and Lenovo 90W AC Adapter or 65W AC Adapter, which ship with Lenovo ThinkPads and can be purchased separately.
External unit frees up your ThinkPad notebook so you can continue to work off the system battery while charging a spare battery to increase your unplugged mobile computing time.

Supports: T,R,L,X,Z,SL,Edge & W Series ThinkPad Batteries.

Supported, but not in charging cradle. Battery is connected beside charger:
ThinkPad Battery 27++ (9 Cell) Slice T410/T420, T510/T520 & W510/W520 Series [57Y4545]
ThinkPad Battery 39+ (6 Cell) Slice X1 Series [0A36279]
ThinkPad Battery 42 (3 Cell) Bay [57Y4536]
ThinkPad Battery 50 (3 Cell) Bay X300/301 Series [43R1966]

Does Not Support:
ThinkPad Battery 12 (4 Cell) X200/X201 Tablet Series [43R9256]
ThinkPad Battery 12+ (8 Cell) X200/X201 Tablet Series [43R9257]
ThinkPad Battery 52+ (6 Cell) X220 Tablet Series [0A36286]
ThinkPad Battery 64++ (8 Cell) X60/X61 Tablet Series [40Y8318]
ThinkPad Battery 19+ (6 Cell) Slice X220 & X220 Tablet Series [0A36280]