Extra throughput versus days lost in V2G services: Influence of dominant degradation mechanism

Electric vehicle (EV) batteries are often underutilized. Vehicle-to-grid (V2G) services can tap into this unused potential, but increased battery usage may lead to more degradation and shorter battery life. This paper substantiates the advantages of providing load-shifting V2G services when the battery is aging, primarily due to calendar aging mechanisms (active degradation mechanisms while the battery is not used). After parameterizing a physics-based digital-twin for three different dominant degradation patterns within the same chemistry (NMC), we introduce a novel metric for evaluating the benefit and associated harm of V2G services: throughput gained versus days lost (TvD) and show its strong relationship to the ratio of loss of lithium inventory (LLI) due to calendar aging to the total LLI ( LLI Cal / LLI ). Our results which focus systematically on degradation mechanisms via lifetime simulation of digital-twins significantly expand prior work that was primarily concentrating on quantifying and reducing the degradation of specific cells by probing their usage and charging patterns. Examining various cell chemistries and conditions enables us to take a broader view and determine whether a particular battery pack is appropriate for load-shifting V2G services. Our research demonstrates that the decision ”to V2G or not to V2G” can be made by merely estimating the portion of capacity deterioration caused by calendar aging. Specifically, TvD is primarily influenced by the importance of aging while EV is at rest and the environmental temperature where the car is parked, while the usage intensity and charging patterns of EVs play a lesser role. • Physics-based simulation of V2G for three distinct aging patterns • A new metric to quantify V2G impact: throughput gained versus days lost (TvD) • Qualification of the popular belief: “Use it or lose it” • The fraction of calendar aging to overall aging is the key factor for V2G impact • Charging protocols and driving behaviors are secondary factors