The Effect of Driving Conditions and Ambient Temperature on Light Duty Gasoline-electric Hybrid Vehicles (3): Battery Energy

The dependence of gasoline-electric hybrid vehicle energies on driving conditions and ambient temperature is presented for different drive cycles (2xLA4, 2xLA92, 2xUS06, HWFET and 2xNYCC) and temperatures (20°C and -18°C). The tests were carried out at the Emissions Research and Measurement Division of Environment Canada. Hybrid battery pack current was measured at a frequency of 10 Hz. Regenerative braking energy, charging energy from the engine and battery discharge energy were estimated by using modal speed. The magnitudes of battery energies were found to be directly related to drive cycle properties. Battery discharge energy was very strongly correlated to emission factors of CO₂, while energy recovered by regenerative braking and charging energy from the engine had low to very strong correlations to CO₂ emission factors. CO, NO_x and HC had low linear correlations to battery discharge energy. Augmented braking, a standard dynamometer operation, was found to decrease the potential for an HEV to recuperate braking energy, and in keeping with the recommendations of SAE J1711 (1995) it is recommended that hybrid vehicle testing standards explicitly state that augmented braking not be used during chassis dynamometer tests.