The responsibility to conserve the world we live in has pushed us to find alternative, sustainable solutions that do not harm the environment. Electric vehicles are one such solution that operates without producing any emissions. In 1832, Robert Anderson developed what we know as the first crude version of the electric car. However, it was during the 1870s that this innovation came into practical use.

Electric vehicles run on rechargeable battery packs that are made of multiple cell modules arranged in series and parallel.  These battery packs produce several hundred volts of electricity. Various functions in the car depend on them. That is why it becomes a critical component of the vehicle, requiring constant monitoring and control.

This requires a Battery Management System (BMS), an embedded system that monitors components near the battery cells, as each cell must be closely monitored to prevent voltage fluctuations or imbalances. The BMS consists of components that ensure the battery runs efficiently without the risk of failure.

What is the need for BMS?

The main function of a BMS is to ensure that the battery is protected and that any operation outside its safety limits is prevented. It provides continuous monitoring of the battery pack by tracking critical parameters, including voltage, current, temperature, state of charge (SOC), and state of health. BMS also manages the battery optimization via cell balancing that improves the life of the battery in the long run. The BMS will also monitor voltage, different temperature parameters, and coolant flow while actively managing battery temperature to prevent overheating. It also protects against over-voltage and under-voltage conditions. The system detects faults and provides alerts to support safe operation.

Battery Management System (BMS) for Electric Vehicles, Image Source- Circuit Digest

Lithium-ion batteries that possess high charge density power most electric cars. These battery packs, even though they are not very big, can be highly unstable. Therefore, these batteries should never be overcharged or allowed to reach deep discharge. Thermal Runaway is a condition in which the current flowing through the battery during charging or overcharging causes the cell temperature to rise. Conditions like these can harm the lifespan or the capacity of the battery. To prevent this, we require BMS to monitor its voltage and current.

This process is very challenging because many cells are assembled into a battery pack in an electric vehicle, and each cell must be individually monitored for safety and efficient operation, which requires a dedicated system called the Battery Management System (BMS).

How Does it Aid Battery Charging and Cell Balancing?

Various factors must be considered when designing a BMS, as many of its functionalities depend on the end application for which it will be used.  Let us take a look at some of these functionalities in a little more detail.

• As seen earlier, the main function of the BMS is to ensure that the battery operates within the safety parameters. Since a battery pack is made up of cells rated at 3V, the BMS must ensure the cells in the pack are not discharged beyond 3V. It also regulates cell voltage to prevent overcharging of individual cells, which supports longer battery life.
• Charging control is another area that requires BMS monitoring. The charging is done in two stages. The first stage is Constant Current (CC), in which the charger delivers a constant current to charge the battery. The second stage, called the Constant Voltage (CV), comes into play, where a constant voltage is supplied to the battery at a very low current. The BMS ensures that these functions operate seamlessly.
• All vehicles have a fuel indicator; similarly, EVs have a battery state of charge (SOC) indicator. BMS helps indicate and display the battery’s actual state of charge to the driver. The voltage and current measurements are made using algorithms that calculate the battery pack’s SOC, with voltage monitoring used alongside current-based methods. One method is Coulomb Counting, which measures battery discharge and integrates the discharge current over time to estimate SOC. Newer BMS development also applies control algorithms to improve estimation accuracy.
• In addition to the current state, BMS is also responsible for monitoring the state of health (SOH). The battery’s capacity may degrade over time. The BMS helps determine the battery’s health by measuring its age and expected life cycle based on usage. This will help determine the mileage per charge.

These are some of the key functions of the BMS, which ensure the battery operates efficiently and provide the driver with timely indications of its state and condition. eInfochips is a product and silicon engineering company with over 25 years of experience in delivering products from ideation through concept and prototyping.  eInfochips delivers systems and sub-systems right from core automotive product engineering, AUTOSAR-compliant ECU software development, HMI design & testing, to next-gen technology enablement (edge computing, cloud, AI/ML, data analytics).

Battery Management Systems (BMS) play a pivotal role in the electric vehicle (EV) industry, offering a wide array of functions and benefits to ensure the efficient and secure operation of the vehicle’s battery pack.

1. BMS Monitoring: Real-time data enables industries to track and manage the performance and condition of the battery pack. A BMS monitors various battery parameters and critical cell data in real time to regulate performance.
2. Safety Assurance: Ensuring the safety of electric vehicles is paramount for the industry. These features are essential for safeguarding the vehicle, passengers, and surrounding infrastructure.
3. Thermal Management: Industries rely on BMS to prevent overheating during charging, discharging, and extreme environmental conditions, which is critical for the battery’s longevity and safety. It can also activate cooling and heating systems at the battery module level to maintain optimal temperatures and improve battery life.
4. Cell Balancing: In a typical EV battery pack, multiple cells are connected in series and parallel. BMS ensures cell balancing to maintain uniform charge levels across all the cells, sometimes one cell at a time, to improve overall performance and longevity. Active balancing moves charge from higher-SOC cells to lower-SOC cells. Passive balancing dissipates excess charge as heat through resistors.
5. Energy Efficiency: Electric vehicles strive for maximum energy efficiency, and BMS plays a pivotal role in achieving this goal. By preventing over-discharging and effectively managing energy distribution through power management, BMS helps reduce energy waste, optimise energy efficiency, and improve driving range in battery-electric vehicles.
6. Range Estimation: BMS provides real-time data on the battery’s state of charge, which is used to estimate the vehicle’s remaining range. This information is invaluable for both drivers and industries, as it aids in trip planning and mitigates range anxiety.
7. Diagnostics and Proactive Maintenance: BMS offers diagnostic capabilities that enable early detection and resolution of potential battery issues. It also supports the identification of faulty cells and uses secondary data for proactive maintenance. Industries use this feature to minimize downtime and reduce maintenance costs by addressing battery problems before they escalate.
8. Regulatory Compliance: Adhering to safety and performance standards is paramount for EV manufacturers. Industries employ BMS to ensure that their vehicles are fully compliant with regulatory requirements, securing regulatory approval and market access.
9. User Satisfaction: BMS contributes to this by maintaining consistent, reliable vehicle performance, directly impacting user satisfaction and bolstering brand reputation.
10. Warranty Management: Electric vehicle manufacturers offer warranties on their vehicles and battery packs. BMS data empowers industries to efficiently manage warranty claims by identifying when repairs or replacements are necessary, thus reducing warranty-related costs.
11. Data Analytics in BMS: Industries leverage this data to enhance future designs, advance battery technology, and optimise energy management strategies. Advanced BMS systems are moving toward predictive analytics and deeper integration with other vehicle electronic systems for better performance and battery health.
12. Improving Charging Infrastructure: Armed with BMS data, industries can gain a better understanding of EV battery charging behaviour and preferences. This information is invaluable in guiding the development and enhancement of charging infrastructure to meet the needs of EV owners. In summary, Battery Management Systems (BMS) are indispensable in the electric vehicle industry. BMS technology continues to evolve to meet the industry’s ever-changing needs, ensuring the reliability, safety, and performance of electric vehicles as they become increasingly integral in the transportation sector.

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Frequently Asked Questions

1. Can a Battery Management System (BMS) help extend the usable lifespan of an EV battery, and if so, how?

Yes, a BMS extends battery lifespan through advanced cell balancing, temperature regulation, and prevention of overcharge or deep discharge. By keeping each cell within optimal parameters, the BMS reduces wear and degradation, leading to more charge cycles over the battery’s life.

2. How does a BMS contribute to accurate range estimation and what factors can still affect real-world mileage?

A BMS uses real-time data on state of charge, temperature, and battery health to estimate remaining vehicle range. However, driving habits, environmental conditions, and battery age can still cause actual mileage to differ from estimates.

3. What role does the BMS play in proactive maintenance and diagnostics for electric vehicles?

The BMS monitors battery health, identifies faulty cells, and triggers alerts for potential issues before they escalate. This allows for targeted maintenance, reduces unplanned downtime, and can lower long-term costs for EV owners and manufacturers.