A battery pack comprising: - a housing having a bottom portion, oppositely disposed first length side wall and second length side wall extending upward along a length direction of the bottom portion, and oppositely disposed first width side wall and second width side wall extending upward along a width direction of the bottom portion, wherein the housing formed by the bottom portion, the first length side wall, the second length side wall, the first width side wall and the second width side wall is closed in the bottom and the four sides, and has an upper portion opening; - multiple serially-connected battery cells disposed in the housing; and - an upper cover covering the upper portion opening; wherein the housing comprises: - a first step (431.1) and a second step (431.2) configured at two ends of the first length side wall; and - a first metal wiring terminal (421.1) and a second metal wiring terminal (421.2) disposed on the first step (431.1) and the second step (431.2), respectively; wherein the battery pack further comprises a first metal sheet (451.1) and a second metal sheet (451.2), the first metal wiring terminal (421.1) and the second metal wiring terminal (421.2) are disposed at a first end of the first metal sheet (451.1) and a first end of the second metal sheet (451.2), respectively; wherein the battery pack further comprises a first leading-out terminal (424.1) and a second leading-out terminal (424.2), wherein the first leading-out terminal (424.1) and the second leading-out terminal (424.2) are disposed at a second end of the first metal sheet (451.1) and a second end of the second metal sheet (451.2), respectively, such that the first metal wiring terminal (421.1) and the second metal wiring terminal (421.2) are electrically conducted to the first leading-out terminal (424.1) and the second leading-out terminal (424.2), respectively, the first leading-out terminal (424.1) and the second leading-out terminal (424.2) being connected to positive output ends and negative output ends of the multiple battery cells connected in series, respectively; wherein the first end of the first metal sheet (451.1) and the first end of the second metal sheet (451.2) are insert-molded in the housing, and wherein the parts of the housing surrounding the first end of the first metal sheet (451.1) and the first end of the second metal sheet (451.2) comprise a first plastic substrate and a second plastic substrate made of a first plastic material, while other parts of the housing are made of a second plastic material different from the first plastic material, or most of other parts of the housing are made of the second plastic material. - a housing having a bottom portion, oppositely disposed first length side wall and second length side wall extending upward along a length direction of the bottom portion, and oppositely disposed first width side wall and second width side wall extending upward along a width direction of the bottom portion, wherein the housing formed by the bottom portion, the first length side wall, the second length side wall, the first width side wall and the second width side wall is closed in the bottom and the four sides, and has an upper portion opening; - multiple serially-connected battery cells disposed in the housing; and - an upper cover covering the upper portion opening; wherein the housing comprises: - a first step (431.1) and a second step (431.2) configured at two ends of the first length side wall; and - a first metal wiring terminal (421.1) and a second metal wiring terminal (421.2) disposed on the first step (431.1) and the second step (431.2), respectively; - a first step (431.1) and a second step (431.2) configured at two ends of the first length side wall; and - a first metal wiring terminal (421.1) and a second metal wiring terminal (421.2) disposed on the first step (431.1) and the second step (431.2), respectively; wherein the battery pack further comprises a first metal sheet (451.1) and a second metal sheet (451.2), the first metal wiring terminal (421.1) and the second metal wiring terminal (421.2) are disposed at a first end of the first metal sheet (451.1) and a first end of the second metal sheet (451.2), respectively; wherein the battery pack further comprises a first leading-out terminal (424.1) and a second leading-out terminal (424.2), wherein the first leading-out terminal (424.1) and the second leading-out terminal (424.2) are disposed at a second end of the first metal sheet (451.1) and a second end of the second metal sheet (451.2), respectively, such that the first metal wiring terminal (421.1) and the second metal wiring terminal (421.2) are electrically conducted to the first leading-out terminal (424.1) and the second leading-out terminal (424.2), respectively, the first leading-out terminal (424.1) and the second leading-out terminal (424.2) being connected to positive output ends and negative output ends of the multiple battery cells connected in series, respectively; wherein the first end of the first metal sheet (451.1) and the first end of the second metal sheet (451.2) are insert-molded in the housing, and wherein the parts of the housing surrounding the first end of the first metal sheet (451.1) and the first end of the second metal sheet (451.2) comprise a first plastic substrate and a second plastic substrate made of a first plastic material, while other parts of the housing are made of a second plastic material different from the first plastic material, or most of other parts of the housing are made of the second plastic material.