Reliability Modeling Method for Lithium-ion Battery Packs Considering the Dependency of Cell Degradations Based on a Regression Model and Copulas

Lithium-ion batteries are widely used as basic power supplies and storage units for large-scale electric drive products such as electric vehicles. Their reliability is directly related to the life and safe operation of the electric drive products. In fact, the cells have a dependent relationship with the degradation process and they affect the degradation rate of the entire battery pack, thereby affecting its reliability. At present, most research focuses on the reliability of battery packs and assumes that their cells are independent of each other, which may cause the reliability of the evaluation to deviate greatly from the actual level. In order to accurately assess the reliability of lithium-ion batteries, it is necessary to build a reliability model considering the dependency among cells for the overall degradation of lithium-ion battery packs. Therefore, in this study, based on a lithium-ion battery degradation test, the Wiener process is used to analyze the reliability of four basic configurations of lithium-ion battery packs. According to the degradation data of the battery packs, the Copula function is used to quantitatively describe the dependent relationship in the degradation process of a single battery, and the quantitative dependent relationship is combined with the reliability model to form a new reliability model. Finally, taking the battery system of Tesla S as an example, a feasible optimization method for battery pack design is provided based on the model constructed in this work.

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Lithium-Ion Battery Packs Formation With Improved Electrochemical Performance for Electric Vehicles: Experimental and Clustering Analysis

Journal of Electrochemical Energy Conversion and Storage ◽

10.1115/1.4042093 ◽

2019 ◽

Vol 16 (2) ◽

Cited By ~ 9

Author(s):

Liu Yun ◽

Jayne Sandoval ◽

Jian Zhang ◽

Liang Gao ◽

Akhil Garg ◽

...

Keyword(s):

Electrochemical Performance ◽

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Electric Vehicles ◽

Clustering Analysis ◽

Lithium Ion ◽

Internal Resistance ◽

Battery Pack ◽

Self Organizing Map ◽

Battery Packs

With the increase of production of electrical vehicles (EVs) and battery packs, lithium ion batteries inconsistency problem has drawn much attention. Lithium ion battery imbalance phenomenon exists during three different stages of life cycle. First stage is premanufacturing of battery pack i.e., during the design, the cells of similar performance need to be clustered to improve the performance of pack. Second is during the use of battery pack in EVs, batteries equalization is necessary. In the third stage, clustering of spent lithium ion batteries for reuse is also an important problem because of the great recycling challenge of lithium batteries. In this work, several clustering and equalization methods are compared and summarized for different stages. The methods are divided into the traditional methods and intelligent methods. The work also proposes experimental combined clustering analysis for new lithium-ion battery packs formation with improved electrochemical performance for electric vehicles. Experiments were conducted by dismantling of pack and measurement of capacity, voltage, and internal resistance data. Clustering analysis based on self-organizing map (SOM) neural networks is then applied on the measured data to form clusters of battery packs. The validation results conclude that the battery packs formed from the clustering analysis have higher electrochemical performance than randomly selected ones. In addition, a comprehensive discussion was carried out.

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A Framework of Multilayer Multiphase Interleaved Converter for Electric Vehicle Based on Graph Theory

Complexity ◽

10.1155/2020/1657250 ◽

2020 ◽

Vol 2020 ◽

pp. 1-17

Author(s):

Bochao Yang ◽

Pinduan Hu ◽

Teng Li ◽

Dawei Song ◽

Zhifei Shan ◽

...

Keyword(s):

Graph Theory ◽

Energy Storage ◽

Lithium Ion Battery ◽

Large Scale ◽

Lithium Ion ◽

Battery Pack ◽

Equilibrium System ◽

Important Indicator ◽

Average Efficiency ◽

Battery Packs

Lithium-ion batteries play an important role in large-scale energy storage systems. However, the power inconsistency of the battery packs restricts the developments of modern technologies in energy storage area. The motivation of the present study is to serve the growing needs of the energy balance for lithium-ion battery packs. The present study proposes a flexible multiphase interleaved converter for the energy equalization of a lithium battery pack with series configuration. Moreover, the graph theory is applied to the analysis of equalization circuits. It is intended to establish a unified standard for the comparison. The parameter of average efficiency is considered as an important indicator to evaluate the characteristics of the equilibrium system. The proposed method is verified by constructing a lithium-ion battery pack with the equalization circuit. It is observed that the proposed multiphase interleaved converter has flexible characteristics, while it has low energy loss compared with the conventional methods. It is found that the proposed method simplifies the complex equalization circuits into graphs and facilitates the comparison of the average efficiency of the system. It is concluded that this method is a feasible and powerful method for evaluating the battery equalization circuit. This approach can be applied for solving complex problems in other engineering applications.

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Effect of dynamic loads and vibrations on lithium-ion batteries

Journal of Low Frequency Noise Vibration and Active Control ◽

10.1177/14613484211008112 ◽

2021 ◽

pp. 146134842110081

Author(s):

Xia Hua ◽

Alan Thomas

Keyword(s):

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Experimental Studies ◽

Lithium Ion ◽

Battery Pack ◽

Dynamic Loads ◽

Electrical Performance ◽

Mechanical Degradation ◽

Energy Storage Devices ◽

Battery Cell

Lithium-ion batteries are being increasingly used as the main energy storage devices in modern mobile applications, including modern spacecrafts, satellites, and electric vehicles, in which consistent and severe vibrations exist. As the lithium-ion battery market share grows, so must our understanding of the effect of mechanical vibrations and shocks on the electrical performance and mechanical properties of such batteries. Only a few recent studies investigated the effect of vibrations on the degradation and fatigue of battery cell materials as well as the effect of vibrations on the battery pack structure. This review focused on the recent progress in determining the effect of dynamic loads and vibrations on lithium-ion batteries to advance the understanding of lithium-ion battery systems. Theoretical, computational, and experimental studies conducted in both academia and industry in the past few years are reviewed herein. Although the effect of dynamic loads and random vibrations on the mechanical behavior of battery pack structures has been investigated and the correlation between vibration and the battery cell electrical performance has been determined to support the development of more robust electrical systems, it is still necessary to clarify the mechanical degradation mechanisms that affect the electrical performance and safety of battery cells.

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Characterization of the Compressive Load on a Lithium-Ion Battery for Electric Vehicle Application

Machines ◽

10.3390/machines9040071 ◽

2021 ◽

Vol 9 (4) ◽

pp. 71

Author(s):

Seyed Saeed Madani ◽

Erik Schaltz ◽

Søren Knudsen Kær

Keyword(s):

Electrochemical Impedance Spectroscopy ◽

Impedance Spectroscopy ◽

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Electric Vehicles ◽

Large Scale ◽

Electrochemical Impedance ◽

Applied Pressure ◽

Lithium Ion ◽

Battery Cells

Lithium-ion batteries are being implemented in different large-scale applications, including aerospace and electric vehicles. For these utilizations, it is essential to improve battery cells with a great life cycle because a battery substitute is costly. For their implementation in real applications, lithium-ion battery cells undergo extension during the course of discharging and charging. To avoid disconnection among battery pack ingredients and deformity during cycling, compacting force is exerted to battery packs in electric vehicles. This research used a mechanical design feature that can address these issues. This investigation exhibits a comprehensive description of the experimental setup that can be used for battery testing under pressure to consider lithium-ion batteries’ safety, which could be employed in electrified transportation. Besides, this investigation strives to demonstrate how exterior force affects a lithium-ion battery cell’s performance and behavior corresponding to static exterior force by monitoring the applied pressure at the dissimilar state of charge. Electrochemical impedance spectroscopy was used as the primary technique for this research. It was concluded that the profiles of the achieved spectrums from the experiments seem entirely dissimilar in comparison with the cases without external pressure. By employing electrochemical impedance spectroscopy, it was noticed that the pure ohmic resistance, which is related to ion transport resistance of the separator, could substantially result in the corresponding resistance increase.

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Thermal Management of Air-Cooling Lithium-Ion Battery Pack

Chinese Physics Letters ◽

10.1088/0256-307x/38/11/118201 ◽

2021 ◽

Vol 38 (11) ◽

pp. 118201

Author(s):

Jianglong Du ◽

Haolan Tao ◽

Yuxin Chen ◽

Xiaodong Yuan ◽

Cheng Lian ◽

...

Keyword(s):

Lithium Ion Battery ◽

Thermal Management ◽

Thermal Performance ◽

Three Dimensional ◽

Lithium Ion ◽

Battery Pack ◽

Cooling Effect ◽

Air Cooling ◽

Safety Issues ◽

Battery Packs

Lithium-ion battery packs are made by many batteries, and the difficulty in heat transfer can cause many safety issues. It is important to evaluate thermal performance of a battery pack in designing process. Here, a multiscale method combining a pseudo-two-dimensional model of individual battery and three-dimensional computational fluid dynamics is employed to describe heat generation and transfer in a battery pack. The effect of battery arrangement on the thermal performance of battery packs is investigated. We discuss the air-cooling effect of the pack with four battery arrangements which include one square arrangement, one stagger arrangement and two trapezoid arrangements. In addition, the air-cooling strategy is studied by observing temperature distribution of the battery pack. It is found that the square arrangement is the structure with the best air-cooling effect, and the cooling effect is best when the cold air inlet is at the top of the battery pack. We hope that this work can provide theoretical guidance for thermal management of lithium-ion battery packs.

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Thermal Simulation of Phase Change Material for Cooling of a Lithium-Ion Battery Pack

Electrochem ◽

10.3390/electrochem1040029 ◽

2020 ◽

Vol 1 (4) ◽

pp. 439-449

Author(s):

Seyed Saeed Madani ◽

Erik Schaltz ◽

Søren Knudsen Kær

Keyword(s):

Phase Change ◽

Lithium Ion Batteries ◽

Lithium Ion Battery ◽

Phase Change Material ◽

Thermal Management ◽

Lithium Ion ◽

Battery Pack ◽

Thermal Management System ◽

Fast Charging ◽

Change Material

A new heat transfer enhancement approach was proposed for the cooling system of lithium-ion batteries. A three-dimensional numerical simulation of the passive thermal management system for a battery pack was accomplished by employing ANSYS Fluent (Canonsburg, PA, USA). Phase change material was used for the thermal management of lithium-ion battery modules and as the heat transmission source to decrease battery temperature in fast charging and discharge conditions. Constant current charge and discharge were applied to lithium-ion battery modules. In the experimental part of the research, an isothermal battery calorimeter was used to determine the heat dissipation of lithium-ion batteries. Thermal performance was simulated for the presence of phase change material composites. Simulation outcomes demonstrate that phase change material cooling considerably decreases the lithium-ion battery temperature increase during fast charging and discharging conditions use. The greatest temperature at the end of 9 C, 7 C, 5 C, and 3 C charges and discharges were approximately 49.7, 44.6, 38.4, and 33.1 °C, respectively, demonstrating satisfactory performance in lithium-ion battery thermal homogeneity of the passive thermal management system.

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SOH Estimation of Lithium-Ion Battery Pack Based on Integrated State Information from Cells

Applied Sciences ◽

10.3390/app10196637 ◽

2020 ◽

Vol 10 (19) ◽

pp. 6637

Author(s):

Xiaohong Wang ◽

Wenhui Fan ◽

Shixiang Li ◽

Xinjun Li ◽

Lizhi Wang

Keyword(s):

Lithium Ion Batteries ◽

Lithium Ion ◽

Battery Pack ◽

Accurate Estimation ◽

The Novel ◽

State Information ◽

Battery Packs ◽

New Energy ◽

Interactive Relationship ◽

Novel Method

Accompanied by the development of new energy resources, lithium-ion batteries have been used widely in various fields. Due to the significant influence of system performance, much attention has been paid to the accurate estimation and prediction about health status of lithium-ion batteries. In a battery pack, the structure connection causes sophisticated interaction between cells, or between the cells and the pack. Therefore, the degradation of any cell is the result of the deterioration of conjoint cells, and a rapid degradation speed for any individual cell can lead to the accelerated degradation of others beyond expectation, which is one of the primary reasons why the State of Health and life cannot be calculated precisely. To solve this problem, a novel method based on integrated state information from cells has been proposed to estimate status of packs, considering about the degradation effect that cells contribute to the corresponding pack. Using this method, the interactive relationship was described in the form of a neural network in order to mine the effect from the inter-degradation between cells. It was proven that the novel method had better performance than a method based only on the degradation indicators from battery packs.

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Electric Enabler

Mechanical Engineering ◽

10.1115/1.2017-dec-6 ◽

2017 ◽

Vol 139 (12) ◽

pp. 39-39

Author(s):

John Kosowatz ◽

Thomas Romer

Keyword(s):

Production Process ◽

Lithium Ion Batteries ◽

Electric Vehicles ◽

Lithium Ion ◽

Battery Pack ◽

Automated System ◽

Price Point ◽

Battery Packs ◽

Full Capacity ◽

Safety Systems

This article explains how Tesla batteries are making electric vehicles (EVs) affordable for customers. Tesla’s battery revolution began when CEO Elon Musk declared that it would sell a mass-market EV for just $35,000. To produce battery packs cheaply enough to reach that price point, Tesla reengineered not only the production process, but also the factory in which the batteries are made. The Reno, Nev., Gigafactory is not yet operating at full capacity, but it is expected to produce 35 GW per year of lithium-ion batteries, about double the present-day global production. Tesla partnered with Panasonic to revamp the production process, and ended up redesigning the chemistry of the battery itself. The standard “18-650” cell format used thousands of less-expensive commodity cells, similar to lithium-ion batteries used in laptop computers. Tesla replaced individual safety systems built into each cell with an inexpensive fireproof system for the entire battery pack. Now, they have begun producing the new “2170” cell, which delivers higher density through an automated system developed with Panasonic to further reduce costs.

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