Análise térmica e avaliação das incertezas dos parâmetros do modelo elétrico da bateria de lítio-íon

Abstract

Batteries are complex electrochemical systems, whose main application is the storage of energy for use in several areas, such as electric vehicles, mobile devices, telecommunications and power grid. To determine the operating condition of a battery cell, then some parameters inherent to the behavior of the battery cell are determined and estimated, such as State of Charge, Status of Health, Open Circuit Voltage and internal temperature. When the battery cell is subjected to different temperature values, different from that determined as normal temperature and pressure condition, these parameters exhibit a behavior different from that determined by the manufacturer. This temperature, which is considered the ambient temperature, affects the dynamic behavior of the battery cell, degrading the element, reducing its life cycle, reducing its capacity to provide energy to the load associated with the element, allowing greater damages such as fire and explosion. To determine the values of these parameters that define the behavior of the battery cell, based on standards and published works in the bibliography, a load profile was defined to perform the laboratory tests to which the values of the element variables were collected. To repeat the real tests generated through a test bench, a computational model with the same equipments in real environment was developed in a simulation environment. It was then constructed an electric model of the element composed of components as resistance and capacitor, relating to the thermal model of the battery cell, having input variables of the model at room temperature and the current inserted into the battery. With the values of the electrical components, it was possible to determine that for some of these components, there is a higher relation with temperature than with SoC. However, these values do not normally present a consistency, having a variation at each temperature or SOC, being known as uncertainties. These values of the parameters of the simulated tests were compared with the values of the parameters of the actual tests and it was found that there is a relationship between the behavior of the graphs of the two types of tests. Through this analysis, it is possible to evaluate that the batteries present different behaviors according to the variation of the operating conditions and the environment.