Hybrid electric vehicle commercialization issues

Abstract

Summary form only given, as follows. One of the largest issues in commercializing hybrid electric vehicles (HEV) is the cost and life of the batteries. This is particularly true with plug-in HEVs that can provide all-electric operation for a given range. In this study, various hybrid electric vehicle configurations were analyzed for battery size, cost and predicted battery life. Battery lifetimes were calculated based upon a deep-discharge model using various driving scenarios and charging frequencies. Two plug-in HEV models were considered, namely an HEV with a 20-mile all-electric range (HEV 20) and an HEV with a 60-mile all-electric range (HEV 60). Four "real world" driving schedules were analyzed based upon survey responses of approximately 400 drivers. The results from the survey were grouped by one-way daily commute distance. Total annual and all electric miles were calculated for each vehicle configuration and driving schedule, using the survey results. Using all-electric fuel economy and battery size calculated using the NREL ADVISOR model, battery energy use was calculated during each vehicle lifetime for each scenario. Using a deep-discharge model, the number of deep discharge cycles were calculated for each driving situation and vehicle configuration to determine the all-electric battery driving potential in terms of total vehicle miles and calendar years. Based upon the calculations, the HEV 20 had an all-electric battery driving potential of approximately 29000 all-electric miles before the battery degraded below 80% of its original capacity (assumed to occur after 1750 deep-discharge cycles). The HEV 60 had an all-electric battery driving potential of approximately 87000 all-electric miles. Because HEVs also use a gasoline engine to operate in a charge sustaining mode, this all-electric potential translated into 46000 to 174000 total vehicle miles for the HEV 20 and 104000 to 220000 total vehicle miles for the HEV 60, depending upon driving patterns and charging frequency. While in some cases, the HEV 20 might exceed its total battery all-electric driving potential during the vehicle lifetime, there are several methods to mitigate the need for battery replacement. These are explained in this paper. In the event battery replacement is needed, replacement costs are estimated under two commercial scenarios.