Supercapacitors, also known as ultracapacitors, offer an alternative source that substitute or operate in parallel with batteries for motor drive in hybrid electric vehicles (HEV). The supercapacitors have to be series-connected with 60 ones, which have a 162V specification (2.7V per cell), in a pack for applying to HEV. As the impedance of each cell in a pack is different from each others, a cell balancing circuit is mandatory for stable operation. This paper presents electrical equivalent circuit parameters of supercapacitors. After that, several existing cell balancing methods and their advantages and disadvantages are discussed using the parameters. This paper also presents a cell balancing method with flying capacitor and DC/DC converter. The presented method to design a cell balancing circuit with flying capacitor and DC/DC converter by using the electrical equivalent circuit of supercapacitor is an advantageous one because it is easy to simulate, save time and cost.