Aqueous redox flow batteries (ARFBs) represent one promising energy storage technology for integration of renewable energy and balancing the electricity grids because of their technical merits of decoupled energy and power, sustainable and tunable redox active materials, and non-flammable and low cost aqueous supporting electrolytes. Despite numerous new flow battery chemistries reported in the last decade, the cycling life of ARFBs is still primarily limited by the chemical stability of redox active electrolytes. This presentation discusses the proper use and data interpretation of a half-cell flow battery to evaluate the cycling stability of a single redox active electrolyte. Specifically, the half-cell flow battery studies of K₄[Fe(CN)₆]/K₃[Fe(CN)₆] at alkaline conditions using balanced and unbalanced cell configurations will be discussed and compared. Our results reveal that the capacity loss of the K₄[Fe(CN)₆]/K₃[Fe(CN)₆] half-cell is attributed to cyanide ligand dissociation and then subsequent redox degradation. The reported half-cell flow battery methodology can be widely applied to develop new redox active electrolyte materials.