A METHOD OF CHARGING AN ENERGY STORAGE ELEMENT

A method of charging an energy storage element; wherein the energy storage element comprises a plurality of energy storage units arranged for storing electrical energy; wherein the method comprises: determining a voltage of each of the plurality of energy storage units; determining a state-of-the-charge, SoC, of each of the plurality of energy storage units; determining a maximum power voltage, Vmp, of a solar power source; selecting (one or more) energy storage units of the plurality of energy storage units to form a charging set comprising a series and/or a parallel combination of the selected (one or more) energy storage units; wherein the selection is based on the determined maximum power voltage, Vmp, and on a first time period and a second time period associated with a first sun irradiance level and a second sun irradiance level respectively; wherein the selection is further based on a predetermined voltage and state-of-the-charge corresponding to the first and the second time period respectively; controlling one or more switches of the energy storage element to form the charging set; and providing power from the solar power source via a solar power converter to the charging set.