Carbonaceous materials are commonly used to fabricate electrodes for electric double-layer capacitors (EDLCs) or supercapacitors. The high contact resistance between the carbon active layer and the Al current collector can decrease capacitor energy and power performance, and shorten the lifetime of the capacitor. In this report, the sources of carbon based EDLC internal resistance were explored using electrochemical impedance spectroscopy (EIS). An equivalent circuit model was coupled with the EIS data for the analyses. The EDLC cells were made from symmetric carbon/Al electrodes and operated in organic electrolyte. The analysis results showed the effects of pressure and modified Al on the contact resistance, where a novel, carbon modified Al collector with Al4C3 nano whiskers greatly reduced the contact resistance. Finally the effect of scale-up on the internal resistance was discussed.