A system includes an engine and a first coolant thermally coupled to the engine and circulated by a first pump; a hybrid battery pack thermally coupled to a second coolant circulated by a second pump; and an electric component thermally coupled to the second coolant. The system includes a first heat exchanger that transfers thermal energy between the first coolant and the second coolant. The system includes a second heat exchanger that transfers thermal energy between the second coolant and the auxiliary fluid stream having a temperature below a target operating temperature for the hybrid battery pack. The system includes a first bypass for the first or second coolant at the first heat exchanger, a second bypass for the second coolant or the auxiliary fluid stream at the second heat exchanger, and a component bypass for the second coolant at the hybrid battery pack or the electric component.