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Redox flow batteries (RFBs) meet the increasing demand for more effective and scalable energy storage technologies to implement renewable energy sources into the grid. The objective of this study is to determine the most effective combination of composite polymer separators and carbon felts within a aqueous flow battery. The electrochemical characterization of separators and porous felts is critical to overall flow battery performance. Through electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and chronoamperometry (CA) we can determine the charge transfer resistance, mass transfer resistance, and electronic and ionic conductivity in a custom flow cell hardware with various supporting and redox electrolyte chemistries at varying flow rates and at stagnant no-flow conditions. Composite separators for electrochemical characterization including Celgard^TM and Daramic^TM coated with poly(acrylic acid) and poly(vinyl alcohol) hydrogels are studied. Porous carbon felts with varying electronic conductivities are studied to assess the impact on voltaic and Coulombic efficiency performance. The overall electrochemical characterization will help inform the design of aqueous redox flow batteries with cost-effective separators.