Battery Voltage: 3.7V; Capacity: 2400 mAh; Li-Pol; This battery requires a soldering iron for the installation; There are two different version of the TND 740 (TND 740 and TND 740c), one that has a battery that is soldered to the board (TND 740) and a newer (TND 740c) style that is not soldered, this battery is only for the solder version, it does not have a connector that is needed for the newer style of unit.