A battery system is provided. The battery system includes a cooling plate having a housing, an inlet port, and an outlet port. The housing defines an interior region. Both the inlet port and the outlet port fluidly communicate with the interior region. The battery system further includes a solid thermoplastic cooling fin having first and second panel portions. The first panel portion is disposed directly on and against the cooling plate. The battery system further includes a first battery cell disposed directly on and against a first side of the second panel portion of the solid thermoplastic cooling fin. The solid thermoplastic cooling fin is configured to conduct heat energy from the first battery cell to the cooling plate.