NOVELTY - The device for converting chemical energy into electric energy and/or electric energy into chemical energy, comprises a housing, which is opened to a side and is formed in a pressure chamber, and an electrochemical active cell (5) for the energy transformation, where the cell extends itself from the open side (6) of the housing into the housing, and the open side is closed to a plate holding and/or supply of the cell. A sealing element is arranged between the housing and the plate, where the sealing element locks the open side of the housing under formation of the pressure chamber.    USE - Device useful for converting chemical energy into electric energy and/or electric energy into chemical energy, and used as a fuel cell unit and electrolyzer cell unit.    ADVANTAGE - The device ensures simple and economical conversion of chemical energy into electric energy and/or electric energy into chemical energy with less effort.    DETAILED DESCRIPTION - The device for converting chemical energy into electric energy and/or electric energy into chemical energy, comprises a housing, which is opened to a side and is formed in a pressure chamber, and an electrochemical active cell (5) for the energy transformation, where the cell extends itself from the open side (6) of the housing into the housing, and the open side is closed to a plate holding and/or supply of the cell. A sealing element is arranged between the housing and the plate, where the sealing element locks the open side of the housing under formation of the pressure chamber in liquid tight and/or gas-tight manner and is partially formed from an elastic material. The sealing element comprises a pocket (10) extending itself into the pressure chamber in which the cell is present and whose pocket wall is flexible by the elastic material so that the pocket wall is present in an overpressure into the pressure chamber at the cell. The sealing element is held in sections in its edge area (15) at front side of the housing and is fixed by a fastening means. The device has active cells and is formed in the sealing element for each cell of the pocket, where the active cells are formed in planar manner and the pockets lie parallel to each other. The housing comprises two open sides opposite to each other, where the open sides are locked respectively by the sealing element with the pocket, which extends itself respectively from one of the open sides into the pressure chamber and lies parallel next to each other. The sealing element is formed in the form of a stable insert molded frame. The internal dimensions of the pocket are adapted on the geometric outer dimensions of the cell. The sealing element is formed by a cloth and an elongated recess, which comprises two side walls (3) lying opposite to each other. The recess is opened for the open side of the housing. The cloth is present for the formation of the pocket of loop-type into the recesses. The cloth is fixed through battlement, which corresponds in its form of the elongated recesses. The side walls have two or more recesses, where the battlement is held together into the recesses of the side wall enclosed on a battlement bar. The cells have pole plates, where the pole plates facing each other of two adjacent cells are connected together over an electrical, mechanical rigid bridge, which is formed in one-piece manner with the pole plates. The bridge is a part of two lamellas, which extends in the pocket and is present on a pole plate of two adjacent cells. A spacer is present on the base of the pocket. The spacer is an elongated molded part with two longitudinal grooves for the reception of an edge of the pole plates of the cell or the edges of the lamella. The sealing element is formed from a silicone or a flexible polyurethane. The cloth has a thickness of 1-1.5 mm.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic representation of a fuel cell unit.    Base plate (2)    Side walls (3)    Active cell (5)    Open side (6)    Pocket. (10)