By Gary MacDonald, Intersil Corporation
Designing battery management systems (BMS) for electric vehicles (EVs) is one of the more complex design challenges facing engineers, and the most important design consideration is BMS IC selection. This article examines the top three BMS design considerations, including a close look at battery pack architectures, inter-module communications or daisy chaining BMS modules, and the optimum PCB layout configuration.
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For testing ESS Battery Management Systems (BMS), the use of “virtual” batteries is proving to be an effective alternative to the use of real batteries. They allow the engineer to avoid the risks of damage to the batteries – and subsequent costs – while testing and optimizing the BMS design in a close-to-reality loading environment. Maplesoft, a developer of battery modeling technology, recently partnered with ControlWorks, Inc. of South Korea to develop a turn-key BMS system. The end result was a battery model capable of being configured to represent a stack of up to 144 cells that can be connected in any combination of parallel and series networks.
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Battery Cell Voltage Measurement and Balancing system performs high-precision measurement and control of cell voltages in Li-ion batteries.
New rapid control prototyping (RCP) offerings from dSPACE are said to simplify the development of critical battery management algorithms by enabling precise, fast measurement and control of cell voltages for modern Li-ion batteries.
Quick iterations with maximum control
Battery management systems (BMS) interact with several vehicle systems such as the powertrain, energy management, vehicle safety, infotainment, etc. These systems cannot be developed in isolation, but require easy-to-use, in-vehicle rapid control prototyping (RCP) systems that allow quick iterations with maximum control capability. dSPACE is extending its RCP portfolio to fulfill this need by introducing its Battery Cell Voltage Measurement and Balancing system.
dSPACE’s newest Automotive Simulation Models (ASM) simulation package is a battery model for simulating high-voltage rechargeable batteries. The model is designed to virtualize rechargeable lithium-ion, nickel-metal hydride (NiMH) and lead batteries used for the electrification of vehicle drivetrains.
The model facilitates function development for battery management systems (BMS) and the testing of close-to-production electronic control units (ECUs). Model-in-the-loop (MIL) simulations in MathWorks’ Simulink and hardware-in-the-loop (HIL) simulations on the simulator are used for this.
Realistic Battery Simulations
Maxim Integrated Products has introduced the MAX11068, a high-voltage, 12-cell, battery-monitoring IC for hybrid and electric vehicles, among other applications. This highly integrated solution employs a proprietary SMBus™-laddered communication bus that allows multiple MAX11068s to be daisy chained together without expensive isolators. This approach reduces battery-management system (BMS) cost by up to 80%, according to the company, while simplifying battery pack design and precisely balancing cells for maximum energy delivery.
Combining accuracy,low power consumption, built-in safety and diagnostic features, and configurability, the MAX11068 solves the problems associated with safely monitoring large battery stacks and accurately balancing cells.
The MathWorks said that Dongfeng Electric Vehicle (DFEV), a research and development arm of Chinese automotive maker Dongfeng Motor Company, has developed a battery management system within 18 months using MathWorks tools for Model-Based Design. The new battery management system has been installed in Dongfeng’s EQ6110 hybrid electric city bus, which delivers 30% better fuel efficiency than standard city buses while also lowering emissions.
“With Model-Based Design, we have an integrated process for development, from idea through production code generation,” said Dr. Xiaokang Liu, principal engineer at Dongfeng Electric Vehicle. “The MathWorks tools helped us develop key battery management technology using our own expertise, in an environment that facilitated early and continuous verification of our design, all without compromising our high focus on quality.”
August 5, 2009 – Rotoblock Corp. has signed a memorandum of understanding to acquire a privately held firm in China that makes battery management systems for electric vehicles. Rotoblock did not identify the acquisition target, but said the firm’s factory can produce a minimum of 1,500 units per month.
Rotoblock cited a report that China wants to raise its annual production capacity to 500,000 hybrid or all-electric cars and buses by the end of 2011, from 2,100 last year. CSM Worldwide predicts that Japan and South Korea together will be producing 1.1 million hybrid or all-electric light vehicles by then, and North America will be making 267,000.