1500V BMS Level 3 Architecture BAU BCU BMU for Energy Storage System with CAN 485 LAN

1500V BMS Level 3 Architecture BAU BCU BMU for Energy Storage System with CAN 485 LAN

Product Overview
This high voltage battery management system adopts a Level 3 architecture designed for large scale energy storage systems. The three level structure consists of BAU (Battery Array Unit) as the top level controller, BCU (Battery Cluster Unit) as the middle level for each battery cluster, and BMU (Battery Module Unit) as the slave level for module monitoring. The BAU centrally manages multiple battery clusters and communicates with external devices such as PCS, UPS, EMS, air conditioning, liquid cooling, and fire protection systems. This hierarchical design ensures reliable operation, accurate state estimation, and comprehensive protection for high voltage battery arrays up to 1500V.

Level 3 Architecture Explained
First level control is the BAU which manages all clusters in the battery array and serves as the interface to external systems. Second level control consists of BCU1 to BCUm with each BCU managing one battery cluster, collecting cluster battery information, performing high voltage control, and uploading data to the BAU. Third level control includes BMU1 to BMUn with each BMU responsible for collecting individual battery cell voltage, temperature, and other information from the battery module. This architecture supports up to 30 BCUs and up to 40 BMUs per BCU, making it suitable for very large energy storage installations.

BAU Top Level Controller Specifications
The BAU operates on a 9V to 32V power input with typical working current of 200mA at 24V and rated power ≤5W. It features 4 isolated CAN buses, 4 isolated RS485 buses, 1 USB interface for external data storage (default 32GB or 64GB), and 2 LAN interfaces for TCP IP communication. The BAU provides 4 relay drive outputs (RL), 4 dry node outputs (DO rated 2A passive), 2 high level digital inputs (DIH), and 2 low level digital inputs (DIL). It supports up to 30 BCU connections and manages the entire battery array.

BCU Cluster Level Controller Specifications
The BCU operates on 9V to 32V power input with typical working current of 125mA at 24V and rated power of 3W. It includes 3 CAN bus channels (2 isolated, 1 non isolated), 2 isolated RS485 buses, and 1 LAN interface. The BCU provides 8+2 high side outputs (2 channels support PWM output), 9 switch input detection channels, 2 dry node outputs (rated 2A passive), 4 temperature detection channels supporting NTC 10K or 100K, and 3 total voltage detection channels supporting main and negative relay adhesion detection. Total voltage detection range is 12V to 1500V with error ≤0.3 percent. The BCU manages the rated voltage of the battery pack at 1500V with withstand voltage of AC3100V and DC4380V. It supports up to 40 BMUs and detects total current using 2 channels (1 shunt and 1 Hall sensor supporting 5V or 12V) with range -1500A to 1500A and error ≤1 percent FSR (typical 0.5 percent). Insulation testing ranges from 0 to 200KΩ with error <15KΩ below 200KΩ and ≤±15 percent above 200KΩ. The BCU supports automatic addressing via isolated level signal. SOC estimation error ≤5 percent, SOH estimation accuracy ≤10 percent, SOE estimation accuracy ≤5 percent.

BMU Slave Level Specifications
The BMU is available in four variants: BMU16, BMU32, BMU48, and BMU64, indicating the number of voltage acquisition channels (16, 32, 48, or 64 cells). Operating voltage range is 9V to 32V with typical current of 50mA at 12V or 25mA at 24V and rated power ≤0.6W. Each BMU includes 1 CAN communication channel. Voltage acquisition range is 0 to 5000mV (exceeding -0.5V to 6V may damage the AFE). Voltage acquisition accuracy is ±5mV. Temperature detection points are 4 for BMU16, 8 for BMU32, 12 for BMU48, and 16 for BMU64 with accuracy ±2°C. The BMU supports passive balancing with the ability to activate one balancing channel per every 8 channels. It includes 2 dry contact outputs rated 2A passive, 2 analog input detections (high edge detection), and supports CAN bus bootloader burning. Automatic address allocation is supported. The BMU has power supply anti reverse connection and power surge prevention. Working temperature is -40°C to 85°C with storage up to 125°C. Protection level is IP43 (not waterproof). Humidity <95 percent with no condensation. Shock resistance up to 5500m altitude. Vibration resistance: at 10-25Hz amplitude 1.2mm, at 26-500Hz maximum 30 m/s². Drop test: 1.5m, 5 times in horizontal and vertical directions with no PCBA damage or performance change.

Communication and Integration
The Level 3 BMS integrates seamlessly with external systems. The BAU communicates with PCS (Power Conversion System), UPS (Uninterruptible Power Supply), EMS (Energy Management System), HVAC, liquid cooling, and fire protection panels. Multiple CAN and RS485 buses provide isolation for noise immunity. LAN interfaces enable TCP IP connectivity for remote monitoring and control. The USB port allows local data logging and firmware updates.

Key Functions and Protections
The system provides total voltage and current monitoring with high accuracy. Insulation detection ensures safety against ground faults. Relay adhesion detection prevents dangerous welding of contactors. The BCU’s high side outputs can drive external contactors or indicators with PWM capability for soft start. Dry node outputs control external alarms or auxiliary devices. The BMU’s passive balancing extends battery pack life by equalizing cell voltages during charging. Automatic addressing simplifies installation and reduces configuration errors.