How Battery Management Systems for Electric Vehicles Work

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People know that electric vehicles (EVs) play a big role in reducing carbon pollution. However, not many are aware of their impact on automotive technology.

For EVs to be an ideal everyday vehicle, many car engineers, designers, and manufacturers have developed a range of technologies to ensure that fully electric vehicles suit the needs of the modern driver.

Some of these ground-breaking innovations include ultra-fast charging, home EV charge point installer units, and autonomous driving. Another significant piece of technology that has been produced due to EVs is the battery management system (BMS).

What Is a Battery Management System?

 The battery management system (BMS) plays a critical role in ensuring the health and performance of the vehicle’s battery pack. It’s essentially the brain behind the operation, constantly monitoring and controlling various aspects of the battery’s operation to maximise efficiency, safety, and longevity. There are four types of battery management systems in use when developing an EV. There’s the centralised management system (CBMS), distributed battery management system (DBMS), modular, and hybrid.

In a centralised management system, all monitoring and control functions are centralised in a single unit, typically located near the battery pack. A CBMS uses centralised processing to monitor individual cell voltages, temperatures, and other parameters, allowing for precise control and optimisation of battery performance.

A distributed battery management system, on the other hand, distributes its monitoring and control functions across multiple nodes or modules throughout the battery pack. Each module is responsible for monitoring a subset of cells, and communication between modules allows for the coordinated operation of the entire battery pack.

A modular battery management system uses independent units (or modules), each equipped with its own monitoring and control capabilities. These modules communicate with each other and with a central controller to coordinate operation and ensure uniform performance across the battery pack.

Finally, the hybrid battery management system. This BMS integrates elements of both centralised and distributed BMS architectures. It uses centralised processing for overall monitoring and control, while also incorporating distributed modules for cell-level monitoring and balancing.

What Is the Function of a BMS?

 While there are four types of BMS architectures, their functions are primarily the same. Here are some of the common functions that these systems share.

Battery Optimisation

 One of the primary functions of a BMS is to optimise the performance and efficiency of the battery pack. It achieves this by carefully managing the charging and discharging processes to maximise the available energy. At the same time, it also minimises wear and tear on the battery cells as it performs the previous function. Doing so helps extend the driving range of the vehicle and prolong the lifespan of the battery pack, ultimately enhancing the overall driving experience for EV owners.

Thermal Management

 Another critical function of a BMS is thermal management. This involves regulating the temperature of the battery pack to ensure it stays within safe operating limits. EV batteries are sensitive to temperature fluctuations, and extremes of heat or cold can degrade performance and reduce longevity. Thus, the BMS continuously monitors the temperature of individual battery cells and adjusts charging and discharging rates as needed to keep them within an optimal temperature range.

Cell Balancing

 Battery cells within a pack can degrade at different rates due to variations in usage, environmental conditions, or manufacturing tolerances. To prevent this, BMS employs cell balancing, which is the process of equalising the state of charge (SOC) among all the cells to ensure they discharge and recharge uniformly. It redistributes energy between cells during charging or discharging cycles. This helps prevent overcharging of some cells while others remain undercharged, which can lead to capacity imbalances and reduced overall battery performance.

Facilitating Internal and External Communication

 Battery management systems also serve as communication hubs within electric vehicles, facilitating both internal and external communication. Internally, the BMS communicates with various vehicle systems, such as the powertrain and the onboard computer, to coordinate and optimise battery operation based on real-time data and vehicle conditions.

Externally, the BMS interfaces with external devices, such as charging stations or diagnostic tools, to exchange information and coordinate charging sessions or perform diagnostics. This seamless communication ensures efficient operation, enhances user experience, and enables interoperability with external systems, contributing to the overall integration and functionality of electric vehicles.

Protection

 Perhaps one of the most critical functions of a BMS is protection, which means safeguarding the battery pack and the vehicle from potentially harmful conditions or events. The BMS incorporates a range of protective measures, including overcharge protection, over-discharge protection, short-circuit protection, and over-temperature protection, to prevent damage or catastrophic failure of the battery pack. In the event of an abnormal condition or fault, the BMS can trigger safety mechanisms, such as disconnecting the battery or limiting power output, to mitigate risks and ensure the safety of the vehicle and its occupants.

Even though the battery management system makes up one part of the entire electric vehicle, it plays an important role. It’s a crucial component that ensures the vehicle’s battery pack is in good condition and performing efficiently. When the BMS is taken care of and optimised, EV drivers can maximise the use of  their vehicles and enjoy a smooth ride.