NOVELTY - The module has a case (12) defining volume to contain flat electric energy storage elements (8) e.g. electric accumulators. The case forms flat volume with a longitudinal axis and has thickness less than width and length of the case. The case comprises an upper surface (20) or a lower surface (22) supporting a face of one of the storage elements and forming a recess with respect to the thickness of the case. The case is sized for receiving the storage elements placed in a single row along the longitudinal axis of the case on two superimposed levels.    USE - Electric energy storage module e.g. flat dry battery module such as lithium-ion battery module, for use in an electric energy storage unit on a flat bottom part of a baggage compartment of a vehicle (all claimed) such as electric or hybrid vehicle.    ADVANTAGE - The upper surface or the lower surface of the case supports the face of one of the storage elements and forms the recess with respect to the thickness of the case, thus assuring reinforcement of the structure of the case while assuring intimate contact between the electric energy storage elements and walls of the case to permit heat exchange between the elements for efficient and homogeneous cooling of the elements. The case is sized for receiving the elements placed in a single row along the longitudinal axis on superposed levels, thus allowing increased modularity and saving place while assuring satisfactory cooling and functioning of the elements.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a method for positioning an electric energy storage unit on a flat bottom part of a baggage compartment of a vehicle    (2) an electric energy storage unit comprising electric energy storage modules.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a portion of an electric energy storage unit placed on a bottom part of a baggage compartment and covered with a protection plate.    Flat electric energy storage elements (8)    Case (12)    Upper surface (20)    Lower surface (22)    Side face (24)