NOVELTY - The electrochemical energy accumulator apparatus (1) comprises a galvanic cell (2), a diverting device (3) assigned to the galvanic cell, a connecting device assigned to the diverting device, and a heat exchanger device (5) assigned to the connecting device and designed to exchange thermal energy with the connecting device. The heat exchanger device has first and second surface areas, where the first surface area is partially designed for thermal conductive contact of the connecting device. The area of the first surface area is smaller than the area of the second surface area.    USE - Electrochemical energy accumulator apparatus useful in a motor vehicle (claimed).    ADVANTAGE - The electrochemical energy accumulator apparatus can be simply and effectively operated for a long period of time with less energy consumption.    DETAILED DESCRIPTION - The electrochemical energy accumulator apparatus (1) comprises a galvanic cell (2), a diverting device (3) assigned to the galvanic cell, a connecting device assigned to the diverting device, and a heat exchanger device (5) assigned to the connecting device and designed to exchange thermal energy with the connecting device. The heat exchanger device has first and second surface areas, where the first surface area is partially designed for thermal conductive contact of the connecting device. The area of the first surface area is smaller than the area of the second surface area. A temperature measuring device is assigned to the heat exchanger device. The second surface area of the heat exchanger device is to be flowed by a first fluid. The heat exchanger device has a fluid channel, which is flowed through by the first fluid. A conveying device is assigned to the electrochemical energy accumulator apparatus for conveying the first fluid. The heat exchanger device has a material to pass a phase transition at predetermined conditions. The temperature of the phase transition of the first material is adapted to an operating temperature of the heat exchanger device. The heat exchanger device is to be electrically heated or cooled. The electrochemical energy accumulator has an electrode such as cathode, which has a compound with lithium-orthophosphate oxides (LiMPO4), where M is a transition metal cation of the first row of the periodic system of the elements. The compound has superior olivine structure. The electrochemical energy accumulator has a separator, which is not electron conductive or only poor electron conductive and consists of partially material-permeable carrier that is coated with an inorganic material on one side. An organic material is used as partially material-permeable carrier, is designed as non-interweaved non-woven, and is coated with an inorganic ion-conductive material, which is ion-conducted at -40 degrees C to 200 degrees C. The inorganic ion-conductive material has particle with a larger diameter of below 100 nm. INDEPENDENT CLAIMS are included for:    (1) a motor vehicle; and    (2) a method for operating an electrochemical energy accumulator apparatus.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of an electrochemical energy accumulator apparatus with a galvanic cell.    Electrochemical energy accumulator apparatus (1)    Galvanic cell (2)    Diverting device (3)    Connection cable (4)    Heat exchanger device. (5)