Module-level direct coupling in PV-battery power unit under realistic irradiance and load

•Successful unaided operation of the directly coupled PV-battery unit under realistic irradiance and load.•A properly chosen PV-battery pair can maintain a high degree of internal power coupling.•PV energy profile in comparison to energy at MPP confirms very high coupling efficiency of 98.2%.•Direct coupling can be a viable option from the efficiency, cost, reliability or simplicity points of view.