Modification of Enhanced Battery Equivalent Circuit Model

Canada faces a new frontier on the development of technology within the transportation sector. The recent push for electric vehicles (EVs) has set a new benchmark for automakers to strive for zero emissions vehicles by the year 2035. This is motivated by both policies mandated by the Federal Government of Canada and social influence. One of the major challenges to achieve this goal is the integration of battery packs. This involves choosing the proper cells, the corresponding battery management system (BMS), and the algorithm that guarantees the battery pack operates within its acceptable limits. A BMS relies on accurate battery models to perform predictions, where, equivalent circuit models (ECMs) are most practical. However, batteries possessing significant hysteresis cannot be effectively modeled with conventional ECMs, limiting BMS accuracy. Therefore, this study improves ECM accuracy by addressing hysteresis, a key lithium-ion (Li-ion) cell characteristic. In this context, a second-order Thevenin ECM, incorporating dynamic and instantaneous hysteresis is developed and tested on high-nickel-ternary-cathode (HNTC) Li-ion cells. When working with hysteresis models, the hysteresis tuning rate, ¿, is an estimated parameter often defined as a constant and is overlooked in adjusting the rate of hysteresis decay. In this work, a variable gamma is estimated during system identification and examined for different state of charge (SOC) intervals and temperatures. An n-way analysis of covariance (ANCOVAN) is applied to the variable response of gamma and indicates a significant gamma-hysteresis voltage relationship for specific SOC windows. Comparatively through validation of dy??namic and total hysteresis modelling, results also indicate that incorporating instantaneous hysteresis does not necessarily improve overall model performance.