A method of manufacturing a battery pack is disclosed. The method includes placing first and second sets of battery cells in first and second battery cell holders of a battery system assembly press, placing a cooling duct in a gap between the first and second sets of battery cells, and applying a first and second forces to the first and second sets of battery cells to cause the first and second sets of battery cells to respectively press against first and second sides of the cooling duct. The method also includes, while applying the first and second forces, placing the first and second plurality of battery cells in a first tray configured to hold the first and second plurality of battery cells.