An electro-thermal model is generated to predict the internal temperature of an electrochemical double-layer capacitor (EDLC) undergoing high current charging/discharging. The model is capable of predicting the electrical and thermal behavior of a cell over a wide range of operating conditions. Spiral symmetry is used to reduce the heat generation and transfer model from 3D to a pseudo-3D, which runs faster without losing fidelity. Unlike existing models, each element in the developed model retains physical meaning and the electrical model is coupled with a high-fidelity thermal model including material geometries, thermal properties and air gaps. Unequal entropy is calculated using first principles, included in the model and compared to experimental data, and shown to be valid. More entropic heat is generated at the positive electrode than the negative in a typical EDLC, and there is little spatial variation of heat generation rate within the jelly-roll. The heat-transfer model predicts temperature variations within a cell; this study examines these variations for multiple conditions. Whilst undergoing high current charging (2 s, 400 A, 650 F cell), a temperature gradient in excess of 3.5 °C can be generated between the positive terminal and the jelly-roll. The time dependent spatial temperature distribution within a cell is explored.