This paper investigates double layer capacitor (or supercapacitor) thermal modelling. The originality of this work resides in the fact that 4 type K thermocouples are inserted inside a 350 F supercapacitor modified cell. These thermocouples allow supercapacitor internal temperature measurement. Experimental results have shown that the electrical storage device temperature increases in the phase of charge and decreases during the discharge. The developed model takes into account the effect which is due to the reversible heat generation in the supercapacitor. The model is based on heat equation solution and allows temperature distribution determination inside and outside the supercapacitor as a function of the position and of the time. The model is developed for double layer capacitor based on activated carbon and organic electrolyte technology.