A battery pack , comprising: a housing comprising an accommodating chamber ; and a plurality of battery modules disposed in the accommodating chamber and arranged in a horizontal direction; each of the battery modules comprising a plurality of battery cells electrically connected to each other by a plurality of first bus bars ; each of the battery cells comprising a battery case having a first surface , a first and a second electrode terminals disposed on the first surface of the battery case ; the plurality of the battery modules comprise a first battery module (100-1) arranged at one end of the battery pack along the horizontal direction, a second battery module (100-2) arranged at the other end of the battery pack along the horizontal direction; and a third battery module (100-3) arranged between the first battery module (100-1) and the second module (100-2); characterized in that , each of the first and the second electrode terminals of the battery cells in the first battery module (100-1) face toward the second battery module (100-2), and each of the first and the second electrode terminals of the battery cells in the second battery module (100-2) face toward the first battery module (100-1); and the battery case further having a fourth surface facing the first surface ; optionally, the number of the battery modules is an even number, two first surfaces of the battery case in any two adjacent battery modules face each other, or two fourth surfaces of the battery case in any two adjacent battery modules face each other; or, optionally, the number of the battery modules is an odd number, two first surfaces of the battery case in any two adjacent battery modules except the third battery module (100-3) face each other, or two fourth surfaces of the battery case in any two adjacent battery modules except the third battery module (100-3) face each other. a housing comprising an accommodating chamber ; and a plurality of battery modules disposed in the accommodating chamber and arranged in a horizontal direction; each of the battery modules comprising a plurality of battery cells electrically connected to each other by a plurality of first bus bars ; each of the battery cells comprising a battery case having a first surface , a first and a second electrode terminals disposed on the first surface of the battery case ; the plurality of the battery modules comprise a first battery module (100-1) arranged at one end of the battery pack along the horizontal direction, a second battery module (100-2) arranged at the other end of the battery pack along the horizontal direction; and a third battery module (100-3) arranged between the first battery module (100-1) and the second module (100-2); characterized in that , each of the first and the second electrode terminals of the battery cells in the first battery module (100-1) face toward the second battery module (100-2), and each of the first and the second electrode terminals of the battery cells in the second battery module (100-2) face toward the first battery module (100-1); and the battery case further having a fourth surface facing the first surface ; optionally, the number of the battery modules is an even number, two first surfaces of the battery case in any two adjacent battery modules face each other, or two fourth surfaces of the battery case in any two adjacent battery modules face each other; or, optionally, the number of the battery modules is an odd number, two first surfaces of the battery case in any two adjacent battery modules except the third battery module (100-3) face each other, or two fourth surfaces of the battery case in any two adjacent battery modules except the third battery module (100-3) face each other. <EOS>