Rechargeable Direct Carbon Fuel Cells (RDCFCs) using directly supplied carbon black (CB) fuels were successfully demonstrated. Three different supplying methods of CB fuel were investigated focusing on direct contact or non-contact between the CB fuel and the anode. A small amount of CB in contact with the anode effectively enhanced the performance, particularly during initial power generation. When the maximum power density was 33 mW/cm² and 17.5 mW/cm², the fuel utilization was 66% and 74%, respectively. High power density with high fuel utilization was achieved by RDCFCs at the current density where the CO supply rate equaled the electrochemical reaction rate. Increasing the amount of CB led to an improved maximum power density. As fuel, amorphous carbon with a large specific surface area was more suitable than graphite.