The ThinkPad T40 Series High Capacity Li-Ion Battery is a rechargeable system battery for the ThinkPad T40 Series which extends unplugged operating time. ThinkPad T40 Series customers can work longer, unplugged when they use the nine-cell High Capacity Li-Ion Battery in place of the standard six-cell ThinkPad T40 Series Li-Ion Battery. This battery has an output of 10.8V and can be recharged in 4.4 to 7.0 hours, depending on the ThinkPad system usage.