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CAN and Modbus Standardization Practices in Energy Storage BMS Communication
- November 4, 2025
In modern energy storage systems (ESS), the Battery Management System (BMS) is the “intelligent brain” that ensures battery safety, reliability, and performance. Effective communication between the BMS and other system components is critical for monitoring, control, and optimization.
Two widely used communication protocols in BMS are CAN (Controller Area Network) and Modbus, each offering unique advantages. Standardizing these protocols is essential to ensure seamless data exchange, interoperability, and scalability in large-scale ESS deployments.
This article explores best practices for standardizing CAN and Modbus communication in BMS, providing guidance for engineers and project developers.
Overview of BMS Communication Protocols
(1) CAN Protocol
CAN is a high-speed, reliable communication protocol designed for embedded systems. Key features include:
Real-time data transmission: Typical speeds up to 1 Mbps.
Robust error detection: Ensures data integrity via cyclic redundancy checks (CRC).
Multi-node support: Multiple devices (battery modules, PCS, EMS) can communicate on the same bus.
In ESS, CAN is often used for module-level communication, such as monitoring cell voltage, temperature, and state-of-charge (SoC). Its reliability and low latency make it ideal for safety-critical applications.
(2) Modbus Protocol
Modbus is a widely adopted serial communication protocol, commonly used for system-level communication in ESS. Key features:
Ease of integration: Works over RS485, TCP/IP, or Ethernet.
Flexibility: Supports multiple slave devices and hierarchical data structures.
Standardized registers: Facilitates consistent data access for monitoring and control.
Modbus is typically used for communication between the BMS and the PCS, EMS, or SCADA systems, allowing seamless integration with supervisory and control platforms.
Importance of Standardization in BMS Communication
Standardization ensures:
Interoperability: Different modules, PCS, and EMS can communicate without custom integration.
Scalability: Systems can be expanded with additional modules without redesigning communication protocols.
Data consistency: Uniform definitions for key parameters (voltage, current, temperature, SoC, SoH) reduce errors in monitoring and control.
Safety and reliability: Consistent communication ensures timely fault detection and protective actions.
Without standardization, ESS projects may face integration challenges, increased commissioning time, and higher operational risks.
CAN Standardization Practices
(1) Frame Structure and ID Mapping
Use standardized 11-bit or extended 29-bit identifiers.
Assign unique IDs for each battery module, sensor, and PCS interface.
Ensure consistent data payload formats for voltage, temperature, and current readings.
(2) Data Rate and Timing
Adopt a fixed communication rate (e.g., 500 kbps for mid-size ESS, 1 Mbps for high-performance systems).
Implement synchronized polling intervals for module-level data to avoid bus congestion.
(3) Error Handling and Redundancy
Enable cyclic redundancy check (CRC) for each frame.
Use redundant communication paths for critical safety signals in large ESS systems.
Modbus Standardization Practices
(1) Register Mapping and Function Codes
Define a standardized register map for key battery parameters: voltage, current, SoC, SoH, temperature, and alarms.
Use standard Modbus function codes (read holding registers, write single/multiple registers) to ensure consistent control and monitoring.
(2) Communication Hierarchy
Organize slave devices by logical addressing, allowing scalable system design.
Implement master-slave polling schedules to avoid communication collisions.
(3) Integration with PCS and EMS
Use consistent data types and units across all devices.
Standardize alarm and fault codes for clear event reporting to supervisory systems.
Combined CAN & Modbus Architecture in ESS
A typical ESS communication architecture combines both protocols:
CAN bus for internal module-level communication, collecting real-time battery data.
Modbus for system-level communication, transmitting aggregated data from BMS to PCS, EMS, and cloud platforms.
This hybrid approach leverages the low-latency, high-reliability features of CAN with the flexibility and integration capabilities of Modbus, creating a robust and scalable communication framework.
Best Practices for Implementation
Define standard data models for all battery parameters.
Document CAN IDs and Modbus register maps for all modules and devices.
Implement diagnostic tools to monitor bus health and detect anomalies.
Use layered communication architecture to separate safety-critical and supervisory data.
Ensure compliance with international standards, such as ISO 11898 (CAN) and IEC 60870/Modbus specifications.
Real-World Applications
FFD POWER ESS projects implement these standardized practices to achieve:
Seamless integration of multiple battery modules and PCS.
Reliable fault detection and system-wide alarm reporting.
Efficient cloud monitoring and AI-based energy optimization.
Reduced commissioning time and operational risk.
Conclusion
Standardization of CAN and Modbus communication in BMS is critical for building safe, reliable, and scalable energy storage systems. By following best practices in frame structures, register mapping, polling schedules, and error handling, ESS operators can achieve consistent monitoring, faster integration, and long-term operational efficiency.
FFD POWER integrates these standards in its BMS solutions, ensuring that every energy storage project meets the highest requirements for safety, reliability, and interoperability.