A battery cell assembly, comprising: a first battery cell having a first housing and first and second electrical terminals (52, 54) extending from the first housing; a second battery cell having a second housing and first and second electrical terminals (62, 64) extending from the second housing; and a cooling fin disposed against the first housing of the first battery cell and against the second housing of the second battery cell, first and second rectangular ring-shaped frame members (20, 22), the cooling fin and the first and second battery cells (30, 32) being disposed between the first and second rectangular ring-shaped frame members (20, 22), the cooling fin having a substantially rectangular-shaped plate that extends along a longitudinal axis, the substantially rectangular-shaped plate having a plate portion with a first side and a second side, the first side having a first plurality of recessed regions and a first plurality of flat regions, each recessed region of the first plurality of recessed regions being disposed between two flat regions of the first plurality of flat regions along the longitudinal axis, the first housing of the first battery cell being disposed against the first side such that the first housing contacts the first plurality of flat regions, the second side having a second plurality of recessed regions and a second plurality of flat regions, each recessed region of the second plurality of recessed regions being disposed between two flat regions of the second plurality of flat regions along the longitudinal axis, the second housing of the second battery cell being disposed against the second side such that the second housing contacts the second plurality of flat regions, characterized in that each recessed region of the first plurality of recessed regions is disposed opposite to a respective flat region of the second plurality of flat regions, and each flat region of the first plurality of flat regions is disposed opposite to a recessed region of the second plurality of recessed regions, each recessed region of the first plurality of recessed regions extends perpendicular to the longitudinal axis and extends across at least two-thirds of a width of the plate portion, each recessed region of the second plurality of recessed regions extends perpendicular to the longitudinal axis and extends across at least two-thirds of a width of the plate portion, and the substantially rectangular-shaped plate further includes first, second, third, and fourth peripheral edge portions (82, 84, 86, 88) coupled to and extending from the plate portion, the cooling fin further having a tube coupled to the first, second, third, and fourth peripheral edge portions (82, 84, 86, 88), the tube defining an internal flow path therein. a first battery cell having a first housing and first and second electrical terminals (52, 54) extending from the first housing; a second battery cell having a second housing and first and second electrical terminals (62, 64) extending from the second housing; and a cooling fin disposed against the first housing of the first battery cell and against the second housing of the second battery cell, first and second rectangular ring-shaped frame members (20, 22), the cooling fin and the first and second battery cells (30, 32) being disposed between the first and second rectangular ring-shaped frame members (20, 22), the cooling fin having a substantially rectangular-shaped plate that extends along a longitudinal axis, the substantially rectangular-shaped plate having a plate portion with a first side and a second side, the first side having a first plurality of recessed regions and a first plurality of flat regions, each recessed region of the first plurality of recessed regions being disposed between two flat regions of the first plurality of flat regions along the longitudinal axis, the first housing of the first battery cell being disposed against the first side such that the first housing contacts the first plurality of flat regions, the second side having a second plurality of recessed regions and a second plurality of flat regions, each recessed region of the second plurality of recessed regions being disposed between two flat regions of the second plurality of flat regions along the longitudinal axis, the second housing of the second battery cell being disposed against the second side such that the second housing contacts the second plurality of flat regions, characterized in that each recessed region of the first plurality of recessed regions is disposed opposite to a respective flat region of the second plurality of flat regions, and each flat region of the first plurality of flat regions is disposed opposite to a recessed region of the second plurality of recessed regions, each recessed region of the first plurality of recessed regions extends perpendicular to the longitudinal axis and extends across at least two-thirds of a width of the plate portion, each recessed region of the second plurality of recessed regions extends perpendicular to the longitudinal axis and extends across at least two-thirds of a width of the plate portion, and the substantially rectangular-shaped plate further includes first, second, third, and fourth peripheral edge portions (82, 84, 86, 88) coupled to and extending from the plate portion, the cooling fin further having a tube coupled to the first, second, third, and fourth peripheral edge portions (82, 84, 86, 88), the tube defining an internal flow path therein.