In a thermal management system where total heat generation during cycling is one of the most salient features and controls the temperature of each cell/battery pack is of interest. Therefore, in this respect, total heat generations were investigated by a 3D-Calvet MS80 calorimeter (Setaram, France) under isothermal conditions at 25 °C in sodium and magnesium batteries. The analysis had shown that the dominant heat sources during charging-discharging were caused by mainly joule heat. Thermal data and various resistances by electrochemical impedance spectroscopy give a relationship to calculate the individual heat.