Battery pack

A battery pack comprising:

• an outer case having an upper wall, a bottom wall extending in a first plane defined by a first direction and a second direction that is perpendicular to the first direction, first and second side walls respectively extending upward from the bottom wall in second and third planes that are parallel to each other and that each extend in the first direction and a third direction that is perpendicular to the first and second directions, and third and fourth side walls respectively extending upward from the bottom wall in fourth and fifth planes that are parallel to each other and that each extend in the second direction and the third direction;
• a battery cell case housed within the outer case;
• first and second battery cells housed in the battery cell case such that a longitudinal axis of each of the first and second battery cells extends in the second direction and parallel to the bottom wall;
• and
• at least one first opening defined in the first side wall;
• wherein:
• the upper wall has a terminal-opening part and a first vent,
• a terminal extends through the terminal-opening part and is electrically connected to the first and second battery cells;
• the longitudinal axes of the first and second battery cells extend parallel to the bottom wall in a sixth plane that is parallel to the third and fourth side walls;
• a first air flow path extends through an interior of the battery cell case between the first and second battery cells and at least a majority of the first air flow path extends in the first direction and parallel to the first plane;
• the first air flow path extends from the first vent to a second vent defined in the third side wall;
• the first side wall faces a first longitudinal end surface of the first and second battery cells;
• a second air flow path extends in the third direction parallel to the second and third planes, the second air flow path being defined between an interior surface of the first side wall and a first exterior surface of the battery cell case such that the first longitudinal end surfaces of the first and second battery cells are disposed in the second air flow path;
• the second air flow path extends from the at least one first opening to the terminal-opening part;
• and
• the first exterior surface of the battery cell case is disposed between the first air flow path and the second air flow path.