NOVELTY - The device (100) has a convection tray (102) i.e. convection metal sheet, arranged at a predefined distance from a cooling surface of an energy storage i.e. heavy-duty battery (110), and forming an intermediate space (114) between the cooling surface and the convection tray. Air in environment of a vehicle (112) flows against the convection tray, which is provided with projections formed as undercuts. A filling channel (104) is assigned to the space for filling the space with cooling fluid i.e. air, in order to connect the convection tray to the storage in a thermal conductive manner.    USE - Device i.e. air conditioner, for cooling an energy storage i.e. heavy-duty battery, of a vehicle e.g. electrical and hybrid vehicles.    ADVANTAGE - The filling channel is assigned to the intermediate space for filling the intermediate space with the cooling fluid i.e. air, in order to connect the convection tray to the energy storage in the thermal conductive manner, so that better heat transportation can be ensured, thus reducing energy consumption for cooling the battery while achieving improved energy efficiency of entire vehicle, and hence reducing emissions, and satisfying battery cooling requirements. The device is operated in autonomous and self-regulating manner, so that utilization of electrically operated additional components i.e. continuous energy-intensive compressors, can be avoided, thus manufacturing simple, energy-efficient and safe device. The convection tray is provided with the projections formed as the undercuts, so that the undercuts hold the cooling fluid in the intermediate space, thus preventing the back flow of the cooling fluid.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a method for cooling an energy storage of a vehicle.    DESCRIPTION OF DRAWING(S) - The drawing shows a side view of a device for cooling an energy storage.    Energy storage cooling device (100)    Convection tray (102)    Filling channel (104)    Heavy-duty battery (110)    Vehicle (112)    Intermediate space (114)