Battery Pack Technology for Automotive Applications
In AABTAM Session 4, automotive-system integrators discussed requirements, challenges, and solutions relative to the integration of energy-storage packs into light-duty vehicles, buses and commercial hybrids, and electric vehicles.
Session Chairman:
Michael Keller,Leader Energy Storage, Volkswagen AG
Since 2010 Mr. Keller has been leading the energy-storage development group at Volkswagen AG. Between 2005 and 2010 he led the Battery Systems development department at Continental Temic, receiving the “Ferdinand Porsche” Prize in Mary 2009 in recognition of the development of the first application of a lithium-ion battery to high-volume vehicle. Mr. Keller studied Electrical Engineering (Automation) in Karlsruhe, Germany. He started his professional career in 1996 as a Development Engineer at a German industry supplier for power electronics and electric motor products before moving to the hybrid system group of Continental Temic.
SESSION AGENDA
Electronic Architecture for Modular Traction Battery Systems Michael Keller, Leader Energy Storage, Volkswagen AG
Abstract
The on-going discussion of oil shortage and climate change has led to strong activities on the field of electro-hybrid, plug-in electro-hybrid and battery electric vehicles. The traction battery system of these so called xEVs consists not only of battery cells, but incorporates in addition mechanical, electrical and electronic components like contactors, fuses, plugs, terminals, sensors and control units for example. By performing cell voltage and cell temperature measurement these parts form the prerequisite for a proper cell balancing and battery state estimation, thus allowing a save operation of the battery system with maximum efficiency. Furthermore, they represent the communication interface between vehicle and battery system in form of the Battery Junction Box (BJB) and the Battery Management Controller (BMC). The latter one represents the most important control unit of the traction battery and monitors the cell state of charge and health as well as the general status of the traction battery allowing a safe and proper operation under all ambient conditions.
Comparable to the modular construction kit concept of Volkswagen AG which pools hardware components as well as monitoring and control functionalities within dedicated modules, additional volume and synergy effects can be achieved by modularisation of the traction battery system, standardisation of its components and implementation of the resulting standard modules in all vehicle platforms.
Therefore, a further cost reduction can be achieved with minimum effort when developing the next generation traction battery system for Volkswagen vehicles. Furthermore, the module strategy allows an easy implementation of advanced hardware technologies like active cell balancing or a replacement of electro-mechanical contactors by semiconductor switches. Last but not least, externally supplied software modules can be integrated without a comprehensive modification and adaptation of the complete software architecture.
In the presentation the requirements for monitoring and control functionalities as well as the specification for the vehicle to battery interface will be exemplified. The actual state of the art will be introduced in form of the Volkswagen module strategy and the special advantages will be described. Finally, the resulting boundary conditions of the hard- and software development process for the suppliers will be pointed out and the associated potential will be summarised.
Close Abstract
Challenges of Modular Battery Design for Electric Vehicles Dr. Arno Perner, Head of Battery Concepts and Cell Technology, BMW AG
Abstract
EV and PHEV development is a clear focus of the sustainability strategy of BMW Group. The presentation gives an overview of the main challenges of battery design for electric vehicles.
Safety: For safety there is no compromise. The battery safety is guaranteed by multiple, redundant, and layered safety systems, which are both passive and active, and which utilize both firmware and hardware. Different safety levels are considered:
cell level (Intrinsic safety of the cells, cell chemistry, cell design)
hardware (positioning in crash-free area, crash tests)
function (electronic monitoring of cell-voltage, redundant deactivation of both HV-pathes incl. system fuse)
software
Life time and reliability:
A major challenge of batteries for EVs is the 10years life time requirement. The aging of the battery is defined by the temperature and driving profile. The presentation will highlight the approach to get reliable measurement and simulation results in order to confirm the life time requirements.
Driving range: Another focus in battery development is the challenge how to increase the electric driving range and therewith the energy density. In the in-house development of modular high-voltage storage systems at BMW, range and service life of the battery is optimized through intelligent operating strategies and optimal heat management. Another important contribution to increasing energy densities is the future cell development. What are the next steps concerning energy density in cell chemistry?
Costs: A modular design, applied to the HV battery and its sub-components, is a key factor for cost reductions during the whole life cycle of electrified vehicle applications. Furthermore standardization is a well-established approach to reduce development and validation efforts as well as production costs in car industry. One of the main topics of the modular battery design for multi project reuse is the cell standardization of prismatic hardcase cell types for HEV, PHEV1, EV1 and EV2 cells.
Close Abstract
Battery Monitoring System Design for 48V Systems Bob Shoemaker, Systems Engineering Manager, Texas Instruments
Abstract
This presentation examines the steps necessary for designing a successful 48V battery system. Decisions and options in selecting critical components including the Analog Front End, microcontroller, and discrete components are examined. System specific issues such as communications, ISO26262 requirements, and EMI impact are discussed. A reference design is presented. Testing requirements and results for a successful system are also presented.
Battery Management System Overview
Basic Electrical Requirements
ISO26262 Goals & Requirements
Overhead of Iso Testing
Sampling
Impact on Communications
Communications
Can?
Getting the Daisy Chain to Work
What’s Important
Choosing the Right Analog Front End
Avoiding Waste
Choosing the Right Microcontroller
µc Architecture for Functional Safety (ISO26262)
Minimizing Discrete Component Counts
Controlling Costs
Minimizing Wiring Costs
BCI/EMI/ESD
Bulk Current Injection Testing
Effects on Communications
Effects on Measurements
EMI Testing
ESD Requirements
15kv and Impact on Electronics
Close Abstract
Thermal Management of Li-Ion Batteries in Hybrid Electrical Vehicles Dr. Alfred Jeckel, Manager HV Battery Design, Testing, Thermal Management HV Components, Daimler AG
Abstract
The presentation explains why a Li Ion HV Battery needs to be operated in a certain temperature range. In the development process of an OEM there has to be decided in an early stage what cooling method is applied and what has to be done to heat up the battery in could environments.
The Mercedes HV battery in the S 400 / E 400 will be explained in detail. In the development process the tool of simulation is used very intensive. The simulation results are shown and the results of the corresponding tests will be compared.
The presentation concludes with a summary and discussion
Close Abstract
Thermal Management of Pouch-Cell-Based Battery Systems Dr. Peter Birke, Head of Advanced Cell & Battery Engineering, SK Continental E-motion Germany GmbH
Abstract
With EU-led global CO2 emission targets rapidly converging on 130 g/km by 2015 and 95g/km by 2020, the auto industry has to achieve continuously significant reductions - putting challenges on carmakers to come up with increasing innovative and affordable technical solutions.
Hybrid technologies employing a high power compact Li-Ion battery technology as well as pure electrification by batteries are promising approaches for these targets.
For the optimal combination of energy density, life time and costs the thermal management of batteries plays a decisive role.
At operating periods like momentary peak load, e.g. when braking (recuperation of brake energy) and accelerating (assisted acceleration as boosting), batteries must generate a high power output respectively accept high power within a very short time. These momentary charge/discharge load periods generate high electrical currents, causing self heating of the Li-ion cells due to internal impedance. In warm region the temperature of the vehicle interior can rise temperature above 40°C. But also strategies of heating up batteries at lower temperatures are of high importance.
Pouch cells offer the high advantages of a large surface in combination with a vacuum which can be efficiently used for thermal management. The following presentation will discuss both air and liquid cooled based designs for pouch cells. Thereby also mechanical integration aspects of pouch cells into the system will be highlighted. This will not only be done coming from system aspects but also regarding cell parameters such as optimized chemistry and dimension.
Close Abstract
Analysis of Cooling Requirements and Solutions for Low and High-Voltage Automotive Battery Packs Dr. Peter Pichler, Product Manager Battery Systems, Magna Steyr
Abstract
The load requirements for battery packs for hybrids and electric vehicles and therefore also for the cells are very different. HEV applications request short but high load pulses (up to 40C) and only a very limited useable energy range of approx. 150Wh. Compared to that electric vehicles load the battery pack continuously with low power but utilizing the maximum energy range. As a result the cooling requirements and cooling design for HEV and EV are very different. The presentation will discuss:
Requirements for BEV, PHEV, HEV and 12/48V battery packs
Main parameters and cooling strategies for different applications
Concrete examples of cooling designs for xEV applications including analyses and results.
Close Abstract
Safe Battery Design: Coping with Crash by Mechanical Design and Simulation Dr. Uwe Wiedemann, Product Manager Battery Systems Engineering and Technology, AVL List GmbH
Abstract
It doesn’t matter whether it is a PHEV or a FEV, to fulfill the requirements regarding structural integrity the battery needs to be designed in a proper way. The challenge is to find the right compromise between vehicle structure and battery structure, neither the vehicle nor the battery can take it all alone.
According to legislation, standards and OEM specific requirements, automotive batteries need to fulfill various mechanical requirements for different load scenarios, including e.g. high frequency accelerations profiles, low cycle events, crash loads, loads due to vehicle torsional deformation, thermal cycling, etc. The intended vehicle and the location in the vehicle have major impact on the mechanical design of the battery. Due to packaging and available space restrictions the battery is often located in deformation zones (e.g. middle tunnel), in crash exposed zones (e.g. trunk area), or in relative save zones (e.g. replacing the fuel tank). Thus, the mechanical structure of the battery needs to withstand acceleration pulses, intrusions and deformations under vehicle crash conditions to avoid any critical impact on the cells and high current/voltage carrying parts.
On component level crash simulations are an efficient instrument to analyze, evaluate and optimize the battery pack structure as well as vehicle mounts and battery internal brackets. For this purpose some simulation cases are listed as examples:
Acceleration pulse – according to sled test,
Pole intrusion – according to main standards
The aim for these simulations is to detect and optimize weak points in the battery structure such as:
Rupture of the battery structure and mounting points,
Rupture of brackets,
Clearances between current carrying parts,
Possible deformations of modules/cells,
Forces on connectors and plugs,
Deformations of bus bars.
Based on those evaluation results modification and optimization of the battery pack will be done in the virtual development phase before cost intensive prototypes are build and related safety and abuse tests are conducted. Thus both development cost and time can be reduced and battery safety can be maximized.
