Investigation and Analysis of Wireless BMS and Designing BMS for a Formula Student’s EV Battery Pack

Abstract

In this thesis work, the design challenges of building a robust Battery Management System with the existing solutions are discussed highlighting the communication within the battery pack. The initial plan of this master thesis work was to investigate wireless BMS technologies and to implement a wireless BMS, as a demo prototype for three segments with wired BMS for a full 7.2 kWh battery pack. After investigating the wireless BMS solutions, it was clear that the available resources and support for wireless BMS solutions were limited to use it in real-time application. It also means that the complexity involved in real-time analysis of the antenna, frequency, and battery pack as a wireless channel to build a wireless BMS compatible container was out of this thesis scope.

Due to all these limitations, the thesis work redefined and divided into two sections. In the first section, the problems with wired BMS are discussed and the wireless BMS concept is introduced, with Wireless BMS protocols and technologies were discussed. The commercially available Wireless BMS solutions to use in 2020 are analyzed with design considerations. It concluded by highlighting the advantages and challenges of Wireless BMS.

In the other section, the robust wired BMS is designed for a 7.2 kWh Li-Ion battery pack for a Formula Student Electric Car and compared with conventional BMS design. The highlight is on challenges in housing the BMS inside the battery pack and integration issues with respect to cable harness management. The new BMS communication protocol is discussed and implemented to reduce the complexity of communication inside a battery pack. And BMS design methodology is explained by choosing the topology, components, and design considerations in circuit and PCB development. Later integrating this BMS within the pack is discussed and concluded with the cell testing results, which was done to understand the cell behaviors as an input to design BMS software.

This work gives a better idea about real-time implementation and integration of BMS in the battery pack with design considerations and challenges. It also highlights the technology research on the analysis of futuristic Wireless BMS solutions and its challenges.

Keywords: BMS, Wireless BMS, communication, cable harness complexity, electric vehicle battery pack

Popular Abstract

The major challenge in the transition to electromobility is Battery Storage. Battery management systems (BMS) in Electric Vehicles is to ensure the safe and reliable operation of Lithium-Ion batteries and it plays a very critical role. Current wired BMS solutions suffer from lack of diagnostics, fault-tolerant operation with respect to the physical failure of wire harness, poor scalability, maintenance of wire harness with their weight, and added complexity during assembly, and troubleshooting. Wireless Battery Management Systems are developed as the potential false proof systems in BMS technology because of their high level of scalability, flexibility, fault tolerance, and diagnostics.

In the Wireless BMS concept, the battery pack is built by series or parallel inter-connecting cells, with the integrated wireless cell stack monitoring modules. Each and every wireless monitoring unit integrated with voltage, current, temperature sensors connected to a wireless gateway, which acts as a Master BMS module. So all the sensor nodes communicate with master BMS wirelessly. Through technology research and investigation of wireless BMS, it is clear that they are future of battery management system which eliminates the issues with the present solution. Linear technology’s SmartMesh IP and Navitas Solution’s WiBaAN proprietary protocols are leading ones in this line, with many additional benefits including cable harness elimination. They have proven to be flexible, reliable with low latency, high throughput, and robust communication even in harshest RF environments, with these improvements in this technology, all the semiconductor OEMs are leaning towards it. To implement a wireless BMS, the battery pack should be studied and designed considering it as a wireless channel to achieve reliable wireless communication in it.

The wired BMS can be optimized by moving from conventional CAN bus to isoSPI protocol, which is an isolated 2-wire differential signal encoded with full-duplex SPI signals for BMS communications. It cuts down the cost of additional components required for CAN bus, and also it gives flexibility over BMS architecture, allowing to use any of modular, distributed and centralized communication. It’s more reliable in the moderately high noisy battery pack environment. The efficient BMS using this communication will reduce the entire battery pack cable harness used for signals and the sensors.

In this thesis work, the investigation on wireless BMS solutions is carried out along with the implementation of robust wired BMS using isoSPI from choosing the cells, components, designing electronics to integration. The BMS is designed with just five-set of twisted-pair cables, eliminating more than 400 numbers of cables being used in conventional BMS setup for the same 8KWh, 130 series cells Li-Ion Battery Pack of Lund Formula Student’s first electric car. The Wireless BMS will be the future of BMS and isoSPI is the best-wired alternative for today, which can almost eliminate the complex cable management.

• author: Goragundi Mahesh, Praveen Kumar
• supervisor: Gunnar Lindstedt
• organization: Department of Electrical and Information Technology
• course: EITM02 20201
• year: 2025
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Battery Management System, Wireless BMS, communication, cable harness complexity, electric vehicle battery pack, Li-Ion battery pack
• report number: LU/LTH-EIT 2025-1057
• language: English
• id: 9062339
• date added to LUP: 2025-06-12 14:03:22
• date last changed: 2025-06-12 14:03:22