Optimizing cell and pack design according to the duty cycle of the application requires a careful balance between cell and pack energy, power, manufacturability, abuse tolerance, thermal characteristics,
and cost. This session discussed cell and pack engineering as well as battery monitoring for various large-battery applications.
Session Chairman:
Peter Pilgram, Senior Scientis, Lithium Ion Cell Development, Audi AG
Dr. Pilgram is senior scientist for Li-Ion cell development at AUDI AG since 2010. From 2005 to 2010 he headed the R&D group for electrodes and separators of Evonik Litarion GmbH and Degussa Creavis
GmbH. He started his career in Li-Ion cell development at GAIA Akkumulatorenwerke GmbH in 2002 where he held different position including head of product development. Dr. Pilgram received his PhD
from Technical University of Aachen (RWTH) in polymer chemistry.
SESSION AGENDA
Simulation in Cell and Battery Design Bob Spotnitz, President, Battery Design LLC
This talk surveys the current state of simulation in cell and battery design with an emphasis on identifying opportunities for advancing battery technology.
The area of battery simulation has progressed dramatically in the last ten years as evidenced by the inclusion of battery design in commercial computer aided engineering packages such
as STAR-CCM+. These software tools can be used to design battery packs, cells, and microstructures. In regards to battery pack design, most simulation studies have focused on design
of cooling systems, both air and liquid. The key advance is simulation technology over the last decade is the capability to model how non-uniform heat generation profiles vary with
time, and so design cooling systems capable of controlling temperature uniformity among cells to a tight tolerance.
Cell design has received the most attention. Models can account for the effect of current collector design on current distribution for both stacked plate and spiral cells. This capability
enables optimization of the available energy and power for a given unit cell. Macro-homogeneous models of lithium-ion cells derived from Newman’s work have been extensively
developed and are capable of fitting cell behavior over a wide range of conditions, and even make reasonable predictions. A number of approaches have been proposed to simulate cycle
life and calendar aging, and abuse tolerance, but this work is hardly predictive. The heavy reliance of cell modeling on cell testing highlights the value and opportunity for standardized
testing.
Simulations that account for actual electrode microstructures are now possible as well as simulations based on model-generated random packing of particles. These simulations reveal the
approximate nature of widely used macro-homogeneous models. Microstructure studies highlight the importance of correlating processing steps to product performance. For example, the
specifics of the coating process strongly correlate with the electrode microstructure.
Thermal Design and Simulation for Traction Batteries in Vehicles Wei Zhou, BatteryDevelopmentEngineer, Audi AG
In the automotive industry, there has always been the challenge to reduce the development period of new vehicles, with an ever increasing complexity as well as increased demand for product
quality and innovation. In order to fulfill this challenge, it is essential that possible development conflicts can be discovered and solved in the early development phase. Against this
background, it is very helpful to use computer-based development methods in the automotive industry. This is especially the case for the thermal design of traction batteries in HEV, PHEV
and EV. The thermal design of the batteries is not independent, but it is influenced by other development fields and also has a retroactive effect on these development fields. In this
presentation a model-based design method developed by AUDI AG will be introduced, which is specially used for the developing of battery thermal management system in HEV, PHEV and EV.
The requirements of thermal simulation in the thermal design of traction batteries
Why is thermal management in the traction batteries necessary?
Thermal design in the series-development of traction batteries
A simulation tool to fulfill the requirements in the thermal design
Thermal simulation of traction batteries at AUDI AG
The structure of the simulation tool
Sub-models in the simulation tool
Validation and use case
Validation
Application in the thermal design of traction batteries
Battery Pack Simulation: Multiscale Methods that Achieve Both Speed and Accuracy Lewis Collins, Director of Software Development, Ansys, Inc.
ANSYS Inc develops engineering simulation software that is used for design optimization and virtual validation of automotive systems. This talk describes a tool that can be used for comprehensive
simulation of the multi-physics behavior of a battery pack starting from characterization of individual cells, including service-life and safety considerations. This presentation
specifically covers the following:
Cell electrochemistry modeling
Cell equivalent circuit models (ECM)
3-D cell thermal models and cooling circuit models
Module and pack system simulation and its fusion with 3-D cell models
Reduced-order models (ROMs) for achieving 100x speed-up without sacrificing predictive accuracy
Validation of cell and pack temperature model predictions with experimental measurements
Drive-cycle simulation of thermal-electrical behavior of a pack
Fast Simulation of Physics-based Battery Models John Milios, Chief Executive Officer, Sendyne Corp.
“In-the-Loop” (ILP) battery simulation describes a new broad category of applications where a battery model is bundled with a solver to execute a coupled co-simulation within
another system simulation. Examples include total xEV car simulation, power conversion circuit simulations, Hardware in the Loop (HIL) as well as model-based-control in Battery Management
Systems BMS.
All these types of applications require the battery simulation to run with unpredictable inputs and in pace with the total system. Compact physical models described typically with a set
of Differential Algebraic Equations need to be solved predictably and, in some cases, in real time.
As the characteristics of the solver itself determine to a great extent the speed, robustness and memory requirements of the simulation, in this presentation we will discuss what features
make a solver suitable for executing advanced physical battery models.
We will show the performance of such a solver in two applications:
A battery pack where each cell is modeled individually (reflecting manufacturing variations) along with its thermal interactions with surrounding cells and an active cooling system,
running as a slave co-simulation to a total car simulation performed on the Gamma Technologies platform.
A cell simulation running in real-time on a small ARM processor.
The need for standardization of the interface among different simulators will be finally addressed with a brief presentation of the Functional Mockup Interface (FMI) open standard.
Overview of Modular Software and Function Development for xEVs Sascha Drenkelforth, Project Leader SW-Development Battery Core, Volkswagen
Volkswagen AG develops and produces a broad range of electrified vehicles from micro-hybrid applications to full battery electric vehicles. Key functions of the control strategy of the
vehicles are related to the LiIon batteries being the main energy storage for these applications. Being faced with the contradictory requirements for high power and long range on the
one hand and a long lifetime and low costs on the other hand the Volkswagen AG decided to develop the core software-functions of HV Batteries in house. This follows the general concept
of modularizing the vehicle and the HV-battery. This SW module is to be used in all LiIon Batteries across the group with the advantage of reduced development efforts, identical
and therefore predictable behavior of the batteries and a high quality due to the reuse of mature SW modules.
Starting with a short overview of current electrified vehicle projects at Volkswagen this presentation afterwards introduces the modularization concept of the HV-Batteries at VW in general.
After deriving the corresponding requirements for the development of a software module, which is applicable to various battery sizes, system architectures, cell and/or system suppliers
as well as use cases, the resulting function and SW architecture is presented.
Test Strategies for Lithium-Ion Battery Systems for Automotive Applications Marcus Preissner, Head of the Test Laboratories, Robert Bosch Battery Systems GmbH
Li-ion battery systems for electric vehicles must fulfill challenging automotive requirements due to its manifold functionality and corresponding components,. The development of this technology
requires integration and testing of various components, such as battery cells, modules, battery management system and battery disconnect unit as well as the complete Li-ion battery system.
Integration and testing of the components and of the complete Li-ion battery system is realized with an automotive development process according to the so called V-model. The development
process mirrors the complexity and the hierarchy of the component structure of the Li-ion battery system.
Testing is one of the key elements of the product development process that allows insight into the properties and qualities of our products:
Verify and validate that the product developed and manufactured satisfies the requirements and user needs with minimized test effort, time and cost
Support the development process within the V-model to enable early detection and mitigation of issues by testing appropriate subsystems
This presentation will focus on challenges of test strategies for Li-ion battery systems for automotive applications. Test scope and strategy, field load estimation, usage load estimation
and test equipment will provide a comprehensive view on the methods used to validate the Li-ion battery system and its components.
Pouch vs. Prismatic Cell Module Design Uwe Wiedemann, Project Leader SW-Development Battery Core, AVL List GmbH
In today’s mass just starting mass production of electric and hybrid vehicles both pouch and prismatic metal can cells can be found in the various battery pack systems. The decision
for one or the other type of cells is not always driven by technical reasons only.
Dependent on the specific application and on economical boundary conditions the development of the most cost efficient battery pack concept leads to different cell module design approaches.
Regarding the integration of the modules into an application both cell types have to fulfill the various requirements regarding reliability, safety, durability, cost and manufacturability.
A differentiation can only be achieved if the specific properties of one or the other cell type are turned into an advantage regarding the industrialization of the above mentioned
requirements.
One of the key targets regarding the module design is the reduction of components to the minimum in order to reduce module piece cost.
In the presentation, dedicated module development requirements will be analyzed and their implications for both cell types will be derived. Major requirement groups and aspects that will
be reviewed:
Mechanical integration
Electrical
Thermal conditioning
(Re-) manufacturability
Serviceability
Cost
For both cell types a module design that is developed to be insensitive to production and assembly tolerances are a key for good cost efficiency and manufacturing quality.
