Battery Management System (BMS) – II | Battery Pack Development & Cell Balancing | Passive vs Active Balancing | Lecture 22

A battery pack consists of hundreds or even thousands of individual cells, and ensuring that every cell operates safely and uniformly is one of the most important responsibilities of the Battery Management System (BMS). In this lecture, we explore the development of EV battery packs, beginning with battery pack configuration, safety considerations, material selection, and the importance of proper electrical design to ensure equal charging and discharging of all cells. The lecture also revisits key battery concepts such as State of Charge (SoC), Depth of Discharge (DoD), C-rate, and compares different battery chemistries used in electric vehicles.

The lecture then introduces cell balancing, an essential BMS function that equalizes the State of Charge (SoC) of individual cells to improve battery performance, extend battery life, and enhance safety. Both Passive Cell Balancing and Active Cell Balancing techniques are explained in detail. Passive methods such as Fixed Shunt Resistor and Switched Shunt Resistor balancing are discussed along with their advantages and limitations. The lecture further covers Active Cell Balancing methods based on capacitors, inductors/transformers, and power electronics interfaces using converters such as Flyback and Forward Converters. Their operating principles, efficiency, balancing speed, complexity, and suitability for electric vehicle battery packs are explained with practical balancing circuits and examples.

Topics Covered

Battery Pack Development
Battery Pack Configuration (Series & Parallel Cells)
Battery Safety Considerations
Cell Balancing in EV Batteries
Need for Cell Balancing
Passive Cell Balancing
Fixed Shunt Resistor Method
Switched Shunt Resistor Method
Active Cell Balancing
Capacitor-Based Active Balancing
Inductor/Transformer-Based Active Balancing
Flyback and Forward Converter-Based Cell Balancing
Advantages and Limitations of Different Cell Balancing Techniques

Who Should Watch?

B.Tech. and M.Tech. students
Power Electronics learners
Electric Vehicle enthusiasts
GATE and ESE aspirants
Researchers working on battery technologies and Battery Management Systems (BMS)
Engineers designing EV battery packs and energy storage systems

Recommended References

Gregory L. Plett, Battery Management Systems, Volume I: Battery Modeling, Artech House.
Gregory L. Plett, Battery Management Systems, Volume II: Equivalent-Circuit Methods, Artech House.
Y. Izadi and R. Beiranvand, A Comprehensive Review of Battery and Supercapacitor Cells Voltage Equalizer Circuits, IEEE Transactions on Power Electronics, 2023.
G. Marin-Garcia et al., Battery Types and Electrical Models: A Review, IEEE ROPEC, 2020.

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