Reducing SoC-Management and losses of battery energy storage systems during provision of frequency containment reserve

•Using degrees of freedom during provision of frequency containment reserve substantially decrease the needed energy for SoC-management.•Considering losses, the effectiveness of the degrees of freedom is diminished.•The losses of Battery Energy Storage Systems consisting of several subunits can be substantially reduced by proper distribution of setpoints to the subunits.•A corresponding algorithm to minimize losses is capable of activating subunits in their best efficiency range.•This algorithm to minimize losses allows a better exploitation of the DoF.