Electric Vehicle Battery Replacement Costs Under Realistic Fast Charging Behaviors

Abstract

Fast charging networks are being constructed in the United States based on the assumption that electric vehicles can sustainably fast charge. However, fast charging has been shown to shorten calendar and cycle life across multiple lithium-ion battery chemistries. Public information on degradation is limited for realistically fast charged commercial cells and extensions from academic work on commercial-adjacent chemistries is difficult. Here, we model realistic consumer charging behavior by cycling commercial NCA 21700 and LFP 26650 cells under 20 different fast charging behaviors, mixing fast charging (2C) and Level 2 charging (C/6|C/5) under different voltage bounds and under well-ventilated thermal conditions. The degradation observed in these tests were used in an economic model to estimate the number and present value cost of battery pack replacements over an electric vehicle’s lifetime, in which results map to a worst case, upper bound scenario. Overall, the tested LFP cells showed extremely low rates of degradation compared to the tested NCA cells. Cycling the NCA cells under the most aggressive charging scenario (2.5-4.2V, 100% of charging at 2C) showed more than 100 pack replacements over 8 years and a present value cost of more than $1M. Cycling the LFP cells under equivalent conditions (2-3.65V, 100% of charging at 2C) showed only 0-1 pack replacements.