A9
Battery Simulation

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17:35
conference time (CEST, Berlin)
Cell Venting Within a Simplified 18650 Li-ion Battery Pack
26/10/2021 17:35 conference time (CEST, Berlin)
Room: A
D. Grimmeisen, M. Schneider (Cascate GmbH, DEU)
D. Grimmeisen, M. Schneider (Cascate GmbH, DEU)
Neglection of nominal operating conditions in Li-ion batteries can lead to internal damage and failure of the cells. This usually triggers chemical reactions that produce a large volume of hot gas. As a safety feature, 18650 battery cells are equipped with a safety vent. Once an internal pressure threshold is exceeded, the vent opens and the gas escapes the cell at a high velocity to prevent uncontrolled structural failure. Within a battery pack the hot gas needs to be guided to exit the pack while at the same time keeping neighbouring battery cells cool enough to stay within the nominal operating range. CFD simulation offers the capabilities to explore the mechanism of battery cell venting and flow guidance. This paper describes how such a simulation can be set up and run. Several steps are necessary to achieve this. First, Simcenter Battery Design Studio is used to model the 18650 battery cells. However, it is also described how this step can be avoided if certain prior knowledge about the process is available. Simcenter STAR-CCM+ is used for that and all subsequent steps. The cells are then arranged to a battery module and placed within a simplified battery pack housing. Then, the module is discharged with a constant current while one battery cell is heated by a constant volumetric heat source to model non-nominal behavior. Once this cell reaches a pre-defined average temperature, it is considered to fall in the regime of venting. Thus, in the next step hot gas is inserted into the pack domain through the vent at a high velocity. The gas flows through the pack and escapes through an outlet on the opposing side, passing the neighbouring cells. During this process, the average temperatures of these cells are constantly monitored to evaluate the chance of thermal runaway propagation.
17:55
conference time (CEST, Berlin)
An Automated Battery Module Swelling Simulation Process of Pouch Cell for Battery Module Design Iteration Evaluation
26/10/2021 17:55 conference time (CEST, Berlin)
Room: A
Y. Zhang, S. Song, W. Jiang (Farasis Energy, USA); B. Liu, (ESI-China, CHN); P. Ding (ESI-NA, USA)
Y. Zhang, S. Song, W. Jiang (Farasis Energy, USA); B. Liu, (ESI-China, CHN); P. Ding (ESI-NA, USA)
The swelling of pouch cells caused by lithium intercalation during life-time cycling will lead to degradation of capacity (SOH) loss and varied expansion of the cells. This will result in specific swelling force imposed on module for structural safety risk as well as cell performance concern with the external pressure constraints interacted from the module. The challenge for the design group is to locate a practical and optimal range that balances the energy efficiency, cell performance and strength of the module at concept design stage and during fast iterations of design changes. Swelling Modeling Automation Package is a fast end-to-end workflow, half-automated process templates to speed up the creation, debugging and updating of CAE models to better assist fast design iterations using ESI Virtual-Process as an open and integrated environment that enable efficient product engineering and analysis cross domains. The process is developed to include automated steps of part assemble, material and joint assignment, boundary condition and varied swelling load conditions for Finite Element (FE) modeling of EOL battery swelling stage in module. Additional output definition is developed in the process script for standardized output report and for complete output datasheet for model and design evaluation. Extreme time-efficiency can be achieved through the consistency and further improvement of current CAE processes with reduced order of modeling. This CAE workflow of automation package based on Single Core Model of VPS Solver for Swelling Analysis of Battery. A hypothetic global baseline FE model has been delicately developed for analyzing battery module expansion deformation and corresponding swelling force of pouch battery module at EOL using VPS metric file input. This modeling method has been verified with internal test data and can reach the accuracy of engineering satisfaction. Further reduction of model numerical size and improvement on computational efficiency can also be benificial and be incorporated directly into the current automated work-flow to save time. In general, the process is currently one of the industry-leading tool as one example to streamline the CAD to CAE result with modularized package design for battery pack.
18:15
conference time (CEST, Berlin)
Simulating Battery Thermal Runaway Through Varying Fidelity
26/10/2021 18:15 conference time (CEST, Berlin)
Room: A
K. Illa (Siemens Digital Industries Software, USA); M. Muneki (Siemens Digital Industries, JPN)
K. Illa (Siemens Digital Industries Software, USA); M. Muneki (Siemens Digital Industries, JPN)
It is expected that over the next 10 years the number of new xEV models will be increasing significantly and with that the need to design more efficient vehicle systems with higher ranged vehicle with low cost. With increasingly stringent regulations on emissions, safety regulation and the need to design complex interdependent systems such as e-machines, battery packs, power electronics, radiators, engine surface, and exhaust system. It has become critical to model the drive-train in its entirety especially the thermal management system (TMS) . In this paper we would like to address how battery safety simulation would assist in minimizing the research, analysis, and experiments to analyze the complete behavior of vehicle systems to include where there is a need for strongly coupled resolution of flow, heat transfer, electrochemistry, and combustion during operation to provide the best possible prediction to maintain the integrity. The safety concern for electrical vehicles and other application of lithium-ion batteries is one of the main obstacle that hinders the large-scale adoption of them. Lithium-ion batteries are constantly improving in their energy density, form factor and due to that enhancing their safety is becoming increasingly urgent for the electric vehicle development. Batteries can undergo different multiphysics based abuses which can be by varied from electrical, mechanical and/or thermal abuse but all of these abuse result in thermal runaway (TR). Thermal runaway propagation and mitigation is a key problem which would like to address in this paper. Multiple approaches for thermal runaway are evaluated to limit temperature rise, provide thermal isolation and cost reduction for mitigation. This paper reviews the following approach based on the availability of data, computational time and accuracy – utilizing Accelerated Rate Calorimetry (ARC) test data providing low degree of accuracy but computational efficient, gases which are eliminating during TR act as a fuel which reactive and combustible leading to additional heat generation providing higher degree of accuracy and finally progressing from previous approach is have a multiphase (solid-liquid-gas) fuel which is combustible and providing the highest degree of accuracy. Physically developing and performing trials on new battery compositions and cooling strategies is an expensive and resource intensive process that only large funded organization and laboratories have the facilities to perform successfully. In this paper we would cover the various simulation approaches for thermal runaway via a case study essentially reduces the development time and cost.
Battery, safety, combustion, ARC, gas , venting
18:35
conference time (CEST, Berlin)
Simulating Thermal Runaway of Batteries
26/10/2021 18:35 conference time (CEST, Berlin)
Room: A
N. Karajan, S. Sible (DYNAmore Corporation, USA)
N. Karajan, S. Sible (DYNAmore Corporation, USA)
Driven by the development of electric vehicles, the need for simulation models of batteries on cell, module and pack level has increased tremendously. While models for thermal management during normal use of batteries are already at a very satisfactory level, the misuse cases of batteries as well as the associated thermal runaway remain a challenging field. This presentation will cover the multi physical model building process using LS-DYNA as a solver. Herein, all necessary assumptions and model building techniques will be discussed to setup and calibrate a thermo-mechanically coupled model that is driven by a battery model, which is able to capture normal charge and discharge use cases, short circuiting and thermal runaway. Herein, the focus is not so much on the mechanical model as the application in mind investigates a controlled heating of one cell in a battery pack. Following this, a thermal model will be calibrated using anisotropic thermal conductivity to account for the layered structure in battery cells and isotropic thermal conductivity for the housing of the battery module and pack. Moreover, a thermal contact needs to be defined which accounts for heat transfer via direct contact as well as radiation. The battery model is based on a so-called homogenized Randle circuit approach, where the parameters for the model will be calibrated using several charge and discharge experiments. On top of the battery model sits a short circuit model which can be triggered by either temperature or mechanical deformation. The model for thermal runaway will be included in homogenized fashion using an energy release rate function that is triggered when a critical temperature is reached and calibrated using autoclave tests in a controlled burn environment. Moreover, two CFD approaches will be presented to assess the structural damage in a battery module during thermal runaway as well as the long term heating power of the released gases on neighboring cells.
Battery, Thermal Runaway, Multiphysics, Thermo-Mechanical Coupling,
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