Choosing a good BMU is the key to BMS performance

The Battery Monitoring Unit (BMU) is a crucial component of the Battery Management System (BMS), primarily used for the monitoring and control of individual cells or battery modules. It is also a key technology for ensuring the safety, enhancing the performance, and extending the service life of energy storage products.

Typically, the assessment and prediction of battery status are mainly based on two parameters: State of Charge (SOC) and State of Health (SOH). SOC indicates the remaining battery charge, while SOH reflects the health and service life of the battery.

The BMU, through real-time monitoring of data such as voltage, current, and temperature, can accurately calculate the remaining battery charge, i.e., SOC, which is essential for the energy management of energy storage products. Additionally, the BMU can predict the health status of the battery, i.e., SOH, which helps to identify potential issues in advance and extend the battery life.

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As part of the BMS, the BMU works in conjunction with the Battery Cluster Management Unit (BCMU) and the Battery Array Management System (BAMS) to achieve comprehensive management and protection of the battery. The BMU collects various individual cell information (voltage, temperature), calculates and analyzes the battery's SOC and SOH, implements active balancing of individual cells, and uploads abnormal cell information to the battery pack unit layer BCMU.

To put it metaphorically, the BMU is the "frontline sentinel" in the BMS responsible for bottom-layer data collection and preliminary processing. It ensures the safety and efficiency of the battery pack and is the foundation for the normal operation of the BMS. By working closely with other levels of the BMS, the BMU can achieve comprehensive monitoring and precise management of the battery status.

How to choose a good BMU?

For a BMU, the primary focus should be on accurate monitoring capabilities. A high-quality BMU should have high-precision voltage, current, and temperature sensors to ensure precise monitoring of the battery status. It should also have high-performance data acquisition circuits that can obtain various battery parameters in real-time and accurately.

Furthermore, it needs to have certain communication capabilities, capable of seamless communication with other parts of the BMS, supporting standard protocols such as CANbus, RS485, or I2C. It is also important to choose a BMU that supports passive or active balancing according to the application requirements to ensure the consistency of the battery pack.

Many companies worldwide have launched corresponding BMU products. For example, TI has introduced the TIDA-010271, which retains UART communication for debugging or CAN architecture evaluation, expands NTC channels to meet a 1:1 ratio with the cells, and retains channels for EEPROM and TMUX diagnostics. It also integrates an internal balancing current of 240mA and has automatic thermal management features.

The BMU30 series from Oriental Motor offers a wide range of speed control, suitable for applications that require constant torque from low to high speeds and can perform stable speed control.In addition, companies such as Maxim, TI, and NXP also offer a range of integrated circuits (ICs) for battery monitoring and management, which can serve as core components for building Battery Management Units (BMUs). For instance, Huasux Technology's BMU-S64T52CP1 is designed specifically for liquid-cooled systems, featuring built-in gas and leak detection, integrated fire detection and control at the battery pack level, and individual battery AC internal resistance testing, providing solutions for battery early warning and State of Health (SOH) calculation.

Huawei Digital Energy has also introduced its own BMU, but not as a standalone product; it is part of the Battery Management System (BMS), composed of a Battery Control Unit (BCU) and BMU. The BMU is responsible for sampling the voltage and temperature of individual battery cells and for battery balancing, with features such as compatibility with both high and low voltages, and high-precision State of Charge (SOC) error less than ±3%.

Jiangsu Haishang New Energy also offers BMU products, with models including BMU-YH01-02, BMU-YE02-02-13(32S), BMU-YH02-03, and BMU-YE01-03. These products support battery systems with different voltage ranges, such as 800-1500Vdc or 80-1000Vdc, and have CAN bus communication capabilities. They support various system architectures, including two-tier and three-tier structures, and feature multiple communication interfaces, such as 2 CAN + 2 RS485 + 1 TCP/IP + 1 WiFi (optional). They also have temperature sampling accuracy of ±1°C and current sampling accuracy of 2‰, supporting various power supply methods, including power from the battery cluster or external 24V.

Each company's BMU products have their unique features and advantages, such as support for different battery types, durability in special environments, and advanced algorithms. When selecting a BMU, engineers should carefully evaluate its specific requirements and application environment to determine the most suitable product.

In summary, choosing a good BMU requires a comprehensive consideration of factors such as monitoring accuracy, protection mechanisms, balancing management capabilities, data management, and system security. There are numerous BMU products with different features on the market. Engineers should select the most appropriate BMU based on specific application needs and technical requirements to ensure the efficient, safe, and reliable operation of the Battery Management System.