For high current density operation of redox flow batteries, proper circulation of the electrolytes over the active area of the cell is important. In the present paper, we study experimentally the effect of channel dimensions of a serpentine flow field for vanadium redox flow battery applications. The study encompasses three aspects: effect on the extent of felt intrusion into the flow channels, effect on the pressure drop over a cell for a given electrolyte circulation rate, and effect on the electrochemical performance characterized by a number of parameters. Eight variants of channel and/or rib dimensions in serpentine flow fields have been studied in cells of 400 cm2 and 900 cm2 active area. A lumped parameter model, validated with water and electrolyte circulation data, has been developed to predict the pressure loss and flow apportionment in the cell. The results show that sensitivity to channel dimensions is more keenly felt in the larger cell with noticeable improvements in pressure drop, peak power density and discharge energy density. Increasing channel width and decreasing rib width is recommended as the ideal strategy to improve the overall performance of the cell.