Airport battery ground power unit for supplying electric current to an aircraft parked on the ground, the ground power unit comprising - a first electric battery, - an inverter for transforming an output current of the battery to an alternating output current of the inverter to be supplied to the aircraft, - one or more first electronic switches (60, 80) for connecting and disconnecting the first battery to and from the inverter, wherein the one or more first switches (60, 80) is or are connected in serial to the first battery and wherein the serially connected first battery and the one or more first switches (60, 80) are together connected to the inverter, - a first digital controller unit for controlling at least one of the one or more first switches (60, 80); - a second electric battery; - a second digital controller unit and - one or more second electronic switches (61, 81) for connecting and disconnecting the second battery to and from the inverter, wherein the one or more second switches (61, 81) is or are connected in serial to the second battery and wherein the serially connected second battery and the one or more second switches (61, 81) are together connected to the inverter such that they are in parallel to the serially connected first battery and the one or more first switches (60, 80), wherein at least one of the one or more second switches (61, 81) is controlled by the second digital controller unit, wherein in addition to the one or more first switches (60, 80) being connected in serial to the first battery, a first diode is connected in serial, allowing current from the first battery to the inverter and blocking or limiting current from the inverter or the second battery to the first battery; and wherein in addition to the one or more second switches (61, 81) being connected in serial to the second battery, a second diode is connected in serial, allowing current from the second battery to the inverter and blocking or limiting current from the inverter or the first battery to the second battery. - a first electric battery, - an inverter for transforming an output current of the battery to an alternating output current of the inverter to be supplied to the aircraft, - one or more first electronic switches (60, 80) for connecting and disconnecting the first battery to and from the inverter, wherein the one or more first switches (60, 80) is or are connected in serial to the first battery and wherein the serially connected first battery and the one or more first switches (60, 80) are together connected to the inverter, - a first digital controller unit for controlling at least one of the one or more first switches (60, 80); - a second electric battery; - a second digital controller unit and - one or more second electronic switches (61, 81) for connecting and disconnecting the second battery to and from the inverter, wherein the one or more second switches (61, 81) is or are connected in serial to the second battery and wherein the serially connected second battery and the one or more second switches (61, 81) are together connected to the inverter such that they are in parallel to the serially connected first battery and the one or more first switches (60, 80), wherein at least one of the one or more second switches (61, 81) is controlled by the second digital controller unit, wherein in addition to the one or more first switches (60, 80) being connected in serial to the first battery, a first diode is connected in serial, allowing current from the first battery to the inverter and blocking or limiting current from the inverter or the second battery to the first battery; and wherein in addition to the one or more second switches (61, 81) being connected in serial to the second battery, a second diode is connected in serial, allowing current from the second battery to the inverter and blocking or limiting current from the inverter or the first battery to the second battery. in addition to the one or more first switches (60, 80) being connected in serial to the first battery, a first diode is connected in serial, allowing current from the first battery to the inverter and blocking or limiting current from the inverter or the second battery to the first battery; and wherein in addition to the one or more second switches (61, 81) being connected in serial to the second battery, a second diode is connected in serial, allowing current from the second battery to the inverter and blocking or limiting current from the inverter or the first battery to the second battery.