Effects Of Battery Pack Capacity On Fuel Economy Of Hybrid Electric Vehicles

As a promising trend, hybrid electric technology improves the vehicle fuel economy and lowers the vehicle emission significantly, without making drivers to worry about vehicle charging. The onboard battery pack stores the electric energy generated from the generator driven by regenerative braking and engine and provide the stored electric energy to the motor to drive the vehicle. The capacity of the onboard battery pack in a hybrid electric vehicle has large effects on the vehicle's fuel economy, weight, and cost. If the capacity is too small, only limited electric energy from the regenerative braking can be stored, which results in a worse fuel economy. If the capacity is too high, the engine needs to work harder to drive the generator to charge the battery pack, which also results in a worse fuel economy. Also, a battery pack with high capacity makes the vehicle heavier and more expensive. In this paper, the effects of battery pack capacity on the fuel economy of the hybrid electric vehicle are studied. A hybrid electric vehicle model based on the 2016 Ford Fusion Hybrid is built in GT-SUITE using experimental battery cell data including open-circuit voltage (OCV), 1C-rate charging and discharging voltage, and internal resistance. Five different battery pack capacities (lAh, 3Ah, 5Ah, 7Ah, and 9Ah) are used in the vehicle model to study their effects on the engine fuel consumption rate and overall gas mileage in different standard driving cycles. Based on this research, battery pack capacity between 5Ah to 7Ah is suitable for a mid-sized hybrid electric sedan during most driving conditions.