The sizing process of a supercapacitive tank is today a well-known procedure. It enables the identification of the number of cells needed to match energy requirements. In some cases, this number must be increased, in order to match the power needs of the application with a given efficiency. Due to the internal resistance of supercapacitors, losses by joule effects are in some applications non-negligible. It is then imperative to identify the temperature increase of the cells, and then the processes to cool the tank. This contribution presents a complete sizing procedure of a supercapacitive tank, with a finite element approach to study the temperature constraints on supercapacitors thanks to a simplified thermal model. A complete procedure will be introduced as an illustration, where supercapacitors are used for a pushto-pass function in a racecar.