MULTI-TIER BATTERY PACK HAVING AN INVERTED TIER OF CYLINDRICAL CELLS

A traction battery pack assembly includes a first tier of cylindrical battery cells; and a second tier of cylindrical battery cells. The second tier is inverted relative to the first tier. Another traction battery pack assembly includes an enclosure assembly providing an interior area; a first plurality of cylindrical battery cells disposed on a first tier within the interior area; a second plurality of cylindrical battery cells disposed on a second tier within the interior area; and a busbar assembly sandwiched between the first tier and the second tier. The busbar assembly has a first side contacting first terminals of the first plurality of cylindrical battery cells. The busbar assembly has an opposite, second side contacting second terminals of the second plurality of cylindrical battery cells. A polarity of the first terminals is the same as a polarity of the second terminals.