Uneven temperature and voltage distributions due to rapid discharge rates and different boundary conditions for series-connected LiFePO 4 batteries

Abstract

This paper presents the surface temperature and voltage distributions on a prismatic lithium-ion battery pack at 1C, 2C, 3C, and 4C discharge rates and 5°C, 15°C, 25°C, and 35°C boundary conditions (BCs) for water cooling and ~22°C for an air cooling method to provide quantitative data regarding thermal behaviour of lithium-ion batteries for designing thermal management systems and developing reliable thermal models. In this regard, three large, LiFePO 4 20 Ah capacity, prismatic batteries are connected in series with four cold plates used between cells and eighteen thermocouples are placed at distributed locations on the principle surface of all three cells: the first six for the first cell, the second six for the second cell, and the third six for the third cell, and the average and peak surface temperatures as well as voltage distributions are measured and presented in this study. In addition, using MATLAB Simulink, the simulated heat generation rate, temperature and voltage distributions are validated with an experimental data for the above mentioned C-rates and BCs. The present study shows that increasing discharge rates and BCs results in increase the maximum and average surface temperature at the three locations (first near the anode, the second near the cathode, and the third near the mid surface of the body). The highest value of the average surface temperature is obtained for 4C and 35°C BC (36.36°C) and the lowest value is obtained for 1C and 5°C BC (7.22°C) for water cooling method.

Online Parameter Identification and State of Charge Estimation of Lithium-Ion Batteries Based on Forgetting Factor Recursive Least Squares and Nonlinear Kalman Filter

“…The Thevenin model, which is also called first-order resistor-capacitor (RC) equivalent circuit model, is often used for lithium-ion battery modeling and analysis [38,39]. In this article, the Thevenin model is used as battery model.…”

A Modular Cell Balancer Based on Multi-Winding Transformer and Switched-Capacitor Circuits for a Series-Connected Battery String in Electric Vehicles

“…For the past decades, the series-connected battery string (SCBS) has been widely used in several applications of energy storage systems for electric vehicles (EVs), hybrid electric vehicles (HEVs), subway and electric railroad [1][2][3][4][5][6] that require high voltage and capacity. The balance of the SCBS plays an important role in chemical and electrical characteristics of a battery string.…”

Effects of Temperature Differences Among Cells on the Discharging Characteristics of Lithium‐Ion Battery Packs with Series/Parallel Configurations during Constant Power Discharge

“…However, the equivalent‐circuit model is less well suited to study the influence of the temperature difference on the discharging characteristics of the battery pack because the exothermic phenomena of the battery are not considered in this type of model, where the battery temperature rise is often neglected during the charging/discharging process . Besides, the equivalent‐circuit model cannot accurately capture the dynamic changes of some important characteristic parameters (e.g., cell temperature, Li (Li + ), concentration), because it is difficult to obtain a precise values for the battery resistor and capacitor parameters …”

“…[21] Besides,t he equivalent-circuit model cannot accurately capture the dynamic changes of some importantc haracteristic parameters (e.g.,c ell temperature,L i( Li + ), concentration), because it is difficult to obtain ap recisev aluesf or the battery resistor and capacitor parameters. [22] Theory-basedm odels are oftene stablished by the basic control equations of lithium-ion batteries,a nd these models can essentially reveal the changem echanismso ft he charging/dischargingcharacteristics. [5,20,23] Although severalsimulation studies have been conducted for the lithium-ion batteries,v ery little work has been completed for series/parallel lithium-ion battery packs,e specially quantitative assessments of the imbalance in the discharging process.C hiu et al [19] developedatheory-based model for the series battery pack by integrating the electrochemical models of single batteries (without considering the battery heat-transfer equations), where the battery temperature rise is not considered.…”