A battery module mounting area (105; 205A; 305A; 400A; 500E) of an energy storage system for an electric vehicle (200A; 300A; 600), comprising: a first set of battery module compartments (A...E of FIGS. 2A, 2D or 2E; 300B; 405A) arranged along a first longitudinal side of the battery module mounting area; and a second set of battery module compartments (F...J of FIGS. 2A, 2D or 2E; 300B; 405A) arranged along a second longitudinal side of the battery module mounting area, wherein each battery module compartment in the first and second sets of battery module compartments includes an insertion-side through which a battery module (310A; 315A; 320A; 325A; 330A) is configured to be inserted into the battery module compartment and/or removed from the battery module compartment, characterized in that: the insertion-side of each battery module compartment in the first and second sets of battery module compartments is exterior-facing relative to the electric vehicle and is configured to permit direct access from outside the electric vehicle for the insertion of the battery module into the battery module compartment and/or the removal of the battery module from the battery module compartment while the battery module mounting area remains integrated as part of the electric vehicle, wherein the insertion-side of each battery module compartment in the first and second sets of battery module compartments is configured to be closed via an insertion-side cover (340A; 300C) to form a battery housing with a closed compartment profile that is characterized by each battery module compartment being sealed from at least one other battery module compartment in the battery housing. a first set of battery module compartments (A...E of FIGS. 2A, 2D or 2E; 300B; 405A) arranged along a first longitudinal side of the battery module mounting area; and a second set of battery module compartments (F...J of FIGS. 2A, 2D or 2E; 300B; 405A) arranged along a second longitudinal side of the battery module mounting area, wherein each battery module compartment in the first and second sets of battery module compartments includes an insertion-side through which a battery module (310A; 315A; 320A; 325A; 330A) is configured to be inserted into the battery module compartment and/or removed from the battery module compartment, characterized in that: the insertion-side of each battery module compartment in the first and second sets of battery module compartments is exterior-facing relative to the electric vehicle and is configured to permit direct access from outside the electric vehicle for the insertion of the battery module into the battery module compartment and/or the removal of the battery module from the battery module compartment while the battery module mounting area remains integrated as part of the electric vehicle, wherein the insertion-side of each battery module compartment in the first and second sets of battery module compartments is configured to be closed via an insertion-side cover (340A; 300C) to form a battery housing with a closed compartment profile that is characterized by each battery module compartment being sealed from at least one other battery module compartment in the battery housing. the insertion-side of each battery module compartment in the first and second sets of battery module compartments is exterior-facing relative to the electric vehicle and is configured to permit direct access from outside the electric vehicle for the insertion of the battery module into the battery module compartment and/or the removal of the battery module from the battery module compartment while the battery module mounting area remains integrated as part of the electric vehicle, wherein the insertion-side of each battery module compartment in the first and second sets of battery module compartments is configured to be closed via an insertion-side cover (340A; 300C) to form a battery housing with a closed compartment profile that is characterized by each battery module compartment being sealed from at least one other battery module compartment in the battery housing.