This paper addresses analysis of the principle of a bi-directional electric energy charge pump and describes circuit solution for control unit of a wireless sensor node power subsystem. This power and control unit, as the power subsystem of the wireless node, comprises two supercapacitors. Bi-directional energy flow between these two supercapacitors takes place in order to optimally satisfy the sensor node energy requirements. At the same time, the bi-directional energy flow enables optimal energy harvesting from the selected energy scavenging (harvesting) subsystem. The mentioned Power Unit Control System has been successfully verified in the process of energy harvesting from a solar module.