A battery module, comprising: a plurality of battery cells; a housing, wherein the housing comprises an inner cavity for accommodating the battery cells; an output assembly, wherein the output assembly is electrically connected to the battery cells, and the output assembly is arranged at an outer side of the housing that faces away from the battery cells; and a module upper cover of a plate structure overall, wherein the module upper cover seals the inner cavity, and the module upper cover comprises a body and an extension, wherein the extension is connected to the output assembly; wherein the extension extends from one side or two sides of the body along a length direction of the battery module; wherein the output assembly comprises a sampling output base, and the extension comprises a first extension, wherein the first extension is connected to the sampling output base, and wherein either (i) the first extension is provided with a groove along a width direction of the battery module, and the sampling output base is provided with a first engaging portion, wherein the first engaging portion cooperates with the groove; or (ii) the first extension extends downward along a height direction of the battery module to provide a connection plate, the connection plate being provided with a through hole, and the sampling output base is provided with a first protrusion on a side facing toward the connection plate, wherein the first protrusion fits with the through hole. a plurality of battery cells; a housing, wherein the housing comprises an inner cavity for accommodating the battery cells; an output assembly, wherein the output assembly is electrically connected to the battery cells, and the output assembly is arranged at an outer side of the housing that faces away from the battery cells; and a module upper cover of a plate structure overall, wherein the module upper cover seals the inner cavity, and the module upper cover comprises a body and an extension, wherein the extension is connected to the output assembly; wherein the extension extends from one side or two sides of the body along a length direction of the battery module; wherein the output assembly comprises a sampling output base, and the extension comprises a first extension, wherein the first extension is connected to the sampling output base, and wherein either (i) the first extension is provided with a groove along a width direction of the battery module, and the sampling output base is provided with a first engaging portion, wherein the first engaging portion cooperates with the groove; or (ii) the first extension extends downward along a height direction of the battery module to provide a connection plate, the connection plate being provided with a through hole, and the sampling output base is provided with a first protrusion on a side facing toward the connection plate, wherein the first protrusion fits with the through hole. (i) the first extension is provided with a groove along a width direction of the battery module, and the sampling output base is provided with a first engaging portion, wherein the first engaging portion cooperates with the groove; or (ii) the first extension extends downward along a height direction of the battery module to provide a connection plate, the connection plate being provided with a through hole, and the sampling output base is provided with a first protrusion on a side facing toward the connection plate, wherein the first protrusion fits with the through hole.