This battery adapter cable allows you to plug two batteries with EC3 connectors together in series to power a single speed controller. This cable is built with 14 AWG wire to be able to handle the higher currents of larger aircraft, and has an overall length of 12 cm (5 inches). To use this cable, both batteries must have the same mah capacity. For example, two 3-cell 2200mah batteries can be connected together to form a 6-cell 2200mah battery. You could also connect a 2-cell 2200mah battery with a 3-cell 2200mah battery to make a 5-cell 2200mah battery.