A multitude of factors contribute to the performance of redox flow batteries with organic active material. In this work, experimental and theoretical methods are elucidated to give information about the most important of these: redox potential, kinetic rate constant, diffusion constant, and solubility. They are found to be highly interdependent - especially for different solvents. By implication, novel organic active materials have to be analyzed jointly by chemists, materials scientists, and by reaction and process engineers to propel the redox flow battery as future energy storage device.