The ThinkPad G40 Series Li-Ion Battery is a rechargeable system battery. The system battery option can replace the original battery or can be easily swapped in to extend the unplugged computing time of the ThinkPad notebook. This 12-cell battery option delivers an output of 10.8 V. It can be recharged in as little as 4.5 to 8.5 hours, depending on the ThinkPad system usage while recharging.