Battery of fuel cells comprises at least one stack of interconnected flat two-sided fuel cells arranged inside the thermally insulated chamber. Each two-sided cell is made in a form of a ceramic plate with individual connections for the supply and drainage of fluids and electric power output, and is equipped with the central ceramic anode structure with high electrical conductivity which, on both sides, has channels formed for distribution of fuel and operating channels covered with operating anode layers, which are then covered with solid electrolyte layers, cathode layers and cathode conductive layers. Each two-sided cell (DFC) makes mechanical contact with the neighboring two-sided cells (DFC) with flexible separators which enable transfer of the fuel and catalytic combustion products. Furthermore, inside the thermally insulated chamber, temperature-controlling elements are located, such as heaters, heat absorbers and devices forcing air circulation.