Assessing Impact of Heavily Aged Batteries on Hybrid Electric Vehicle Fuel Economy and Drivability

This paper investigates the impact of battery ageing on the fuel economy and drivability capability of a power-split hybrid electric vehicle (HEV). The HEV is modelled first, an optimal energy management strategy based on dynamic programming is then implemented, and experimental characterization data for the battery cell is presented. The batteries are tested to a heavily aged state, with up to an 84% loss of capacity. Numerical simulations for the HEV performing the WLTP cycle and full power acceleration maneuvers are used to calculate the progressive worsening of fuel economy and rate of acceleration as the battery ages. The fuel economy and acceleration of the vehicle are found to be relatively unaffected until the battery loses more than 20% of original capacity. For the most aged case, with 84% loss of capacity, vehicle fuel economy increases by 25% and 0 to 100 km/h acceleration time reduces by 3.5 seconds compared to performance with a new battery.