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The specificities of temperature-dependent electrochemical modelling strategies of 18650 Li-ion batteries were investigated in pseudo-2D, 2D and 3D domains using finite element analysis. Emphasis was placed on exploring the challenges associated with the geometric representation of the batteries in each domain, as well as analysing the performance of coupled thermal-electrochemical models. The results of the simulations were compared with real reference measurements, where temperature data were collected using temperature sensors and a thermal camera. It was highlighted that the spiral geometry provides the most realistic results in terms of the temperature distribution, as its layered structure allows for a detailed realisation of the radial heat transfer within the cell. On the other hand, the 3D-lumped thermal model is able to recover the temperature distribution in the axial direction of the cell and to reveal the influence of the cell cap and the cell wall on the thermal behaviour of the cell. The effect of cooling is an important factor that can be introduced in the models as a boundary condition by heat convection or heat flux. It has been shown that both regulated and unregulated (i.e., natural) cooling conditions can be achieved using an appropriate choice of the rate and type of cooling applied. [ABSTRACT FROM AUTHOR]

The paper presents a current impulse-based excitation method for lead-acid batteries in order to define the initial electrical parameters for model-based online estimators. The presented technique has the capability to track the SoC (State of Charge) of a battery, however, it is not intended to be used for online SoC estimations. The method is based on the battery’s electrical equivalent Randles’ model [1]. Load current impulse excitation was applied to the battery clamps during discharge while the voltage and current was logged. Based on the Randles’ model, a model function and a fit function were implemented and used by exponential regression based on the measured data. The diffusion-related non-linear characteristic of the battery was approximated by a capacitorlike linear voltage function for speed and simplicity. The initial capacitance of this bulk capacitor was estimated by linear regression on measurements recorded in the laboratory. Then, the RC parameters of the equivalent battery model were derived from exponential regression on transients during each current impulse cycle. The battery model with initial RC parameters is suitable for model-based online observers.

The aim of this work is to present a fast and in situ diffusion modeling technique to extract essential electrochemical parameters from liquid-phase diffusion which can be used to implement a realistic battery in a pseudo-2D finite element modeling environment. A generalized Warburg element was used within an extended Randles equivalent circuit to obtain an appropriate fit on non-ideal diffusion impedance. Based on the calculation method presented in this paper, the values of diffusion-related parameters such as the cross-sectional area of the separator Asep, cell thickness Lcell as well as liquid-phase and solid-phase diffusion coefficients Dl and Ds were derived, successfully. A characteristic cell which allowed the exchange current density i0 and reaction rate constant k0 to be calculated was also established. The experimental data was measured by electrochemical impedance spectroscopy (EIS), resistivity measurement and the galvanostatic intermittent titration technique (GITT). The results show that our hypothesis to extract essential electrochemical parameters from the tail part of diffusion impedance is correct. The applicability of our concept is confirmed by the prosperous validation results produced by computed tomography (CT) and battery dynamics simulation in finite-element environment. Due to the inherent limitations of the pseudo-2D Doyle-Fuller-Newman (DFN) model, our technique is accordingly valid within the current range of 0–1 C. [ABSTRACT FROM AUTHOR]