A Battery Management System or BMS in electric vehicles monitors and controls the battery pack’s operation, ensuring safety and optimising performance by managing parameters like cell voltages, temperatures, and charging processes.
In this blog, we will understand the Importance and need of BMS in Electric vehicles, the Functions of Battery Management Systems, their types and related terms.
What is a Battery Management System in EV?
In electric vehicle applications, rechargeable batteries power auxiliary systems and motors. Lithium-ion batteries are favoured for their high efficiency, low self-discharge rate, wide operating range, high energy density, and long life cycle. To ensure battery quality and safe operation, a Battery Management System (BMS) is used. The BMS oversees various aspects of the battery, such as monitoring cell conditions, balancing cell voltages, managing temperature, and optimising charging and discharging processes. It plays a crucial role in maintaining the health and performance of the battery pack, enhancing safety, and maximising the efficiency of electric mobility.
Importance of Battery Management System in EV
Battery Management System plays an importance in the electric vehicle in the following ways:
- Safety Assurance: BMS monitors cell voltages, temperatures, and currents to prevent accidents and battery damage.
- Enhanced Efficiency: Optimizes battery cell usage, ensuring balanced performance and maximising energy utilisation.
- Prolonged Battery Lifespan: Regulates temperature and balances cells to extend battery life.
- Performance Optimization: Provides real-time data for predictive maintenance and performance tuning.
- Range Optimization: Maximizes driving range by efficient energy utilisation and preventing degradation.
- Regulatory Compliance: Ensures adherence to safety and environmental regulations for EVs.
Functions of BMS
The primary role of a BMS is to meet safety standards, but it also aims to optimise battery cell usage and extend its lifespan. Basic requirements for a BMS include:
- Measurement of individual cell voltages.
- Temperature monitoring at various points near the battery.
- Measurement of currents passing through the system.
- Communication of data to control units and implementation of actions to maintain battery safety.
- Implementation of passive or active cell balancing.
- Provision of thermal management capabilities.
Types of Battery Management Systems in Electric Vehicles
There are two types of Battery Management Systems, namely Centralized BMS and Distributed BMS. A centralised BMS employs a single control unit overseeing all cells, offering cost-effectiveness but posing a risk of total system failure if the control unit malfunctions. In contrast, a distributed BMS enhances system resilience by using multiple control units, albeit with increased complexities and costs. Automotive brands make choices based on their specific needs, with cost favouring centralised BMS and reliability favouring distributed BMS.
Terms Related to BMS
Battery State Parameters
These are indicators used to assess the condition and performance of a battery. They include metrics such as state of charge, state of health, and state of function.
State of Charge
SoC refers to the amount of charge remaining in a battery compared to its full capacity. It is typically expressed as a percentage, with 100% indicating a fully charged battery and 0% indicating a fully depleted one.
State of Health
SoH represents the overall condition or health of a battery. It reflects the battery’s ability to deliver its rated capacity compared to when it was new. SoH can degrade over time due to factors such as ageing, usage patterns, and operating conditions.
State of Function
SoF describes the operational capability of a battery at a given moment. It considers factors such as internal resistance, temperature, and voltage characteristics to assess the battery’s ability to provide power efficiently.
Charge Acceptance
Charge acceptance refers to the battery’s ability to absorb and store energy during the charging process. It indicates how effectively the battery can convert incoming electrical energy into chemical energy for storage, reflecting its charging efficiency and performance.
Conclusion
The Battery Management System is an integral component of electric vehicles, ensuring the safety, efficiency, and longevity of the battery pack. By monitoring and managing various parameters such as cell voltages, temperatures, and charging processes, the BMS plays a crucial role in optimising performance and maintaining regulatory compliance. With its ability to enhance safety, extend battery life, and increase energy usage, the BMS continues to be a key technology driving the advancement of electric mobility.
