How to Build an Efficient Battery Management System (BMS)

When designing a monitor circuit for a new battery-powered system, optimizing cost and manufacturability is a critical task. The first step is to define the system’s preferred structure and the placement of the batteries and associated electronic components. Once the basic structure is clear, the next challenge is to make trade-offs in the circuit topology to optimize communication and interconnects.

Impact of Battery Size on Power System Design

The size of the battery directly affects the overall structure of the power system. Designers must decide whether to use many small batteries to fit into a complex battery module or battery pack, or whether to opt for larger batteries, which may be constrained by weight and size limitations. For example, in automotive design, batteries may be distributed across various spaces in the vehicle, maximizing space utilization if the battery is installed.

Interconnects Between Battery Management System and Testing Signals

An effective Battery Management System (BMS) needs to account not only for the battery itself but also for the interconnects between the battery, module, BMS, and the final application interface for testing and telemetry signals. In many cases, data acquisition circuits are integrated within the battery module or pack so that crucial information, such as production IDs, calibration data, and usage specifications, can be carried with replaceable components, minimizing the number of high-voltage rated wires in the wiring harness.

Battery Measurement Points and Hardware Topology Design

In automotive applications, a BMS may need to support over 100 measurement points, and the modular design of the system will determine how many batteries each circuit system can measure. To ensure safety, battery are often divided into at least two subgroups and isolated via “service plugs,” which ensures that the voltage remains below 200V during failure conditions, minimizing the risk of electrical shock to repair personnel.

Remote Measurement and Data Transmission

In high-efficiency BMS, remote measurement circuits and the CAN bus protocol are used for internal communication between modules. This reduces the data transfer rate and mitigates electromagnetic interference (EMI) issues. The CAN bus protocol allows multiple small processors in the system to share computing tasks, improving overall system efficiency and reliability.

Temperature Management and Battery Capacity Balancing

Battery capacity balancing is crucial for BMS, especially for lithium-ion batteries. Imbalances can lead to heat management issues, affecting long-term performance. Designers need to consider the distribution of temperature probes to accurately correlate the battery’s charge state with voltage readings.

Efficient Battery Monitoring and Data Acquisition

For example, the LTC6803 battery pack monitor IC is an ideal core component for a BMS. This IC provides multi-channel data acquisition functionality, enabling effective voltage measurement of the batteries, along with auxiliary measurements for temperature, calibration signals, and load current.

Energy Efficiency and Cost-Effectiveness in Battery Management Systems

One important improvement in the LTC6803 is its ability to be powered directly by the battery pack, enhancing system efficiency and cost-effectiveness. By performing precise ADC measurements and optimizing battery current control, the LTC6803 reduces battery power consumption and prevents capacity imbalances caused by mismatched battery currents.

Conclusion

Designing a BMS involves many complex factors, especially those directly affecting system packaging and structure. After carefully considering mechanical designs, electronic circuits, and information flow, using scalable data acquisition solutions like the LTC6803 platform can significantly improve system performance and cost-efficiency.