Technical Specifications of Battery Management System for Electric Vehicles
GB/T 38661-2020 specifies the technical requirements for Battery Management Systems (BMS) used in electric vehicles in China. It defines the functional, electrical, and communication requirements that a BMS must meet to support safe and accurate battery operation. The standard was issued by SAC in 2020 and is referenced as part of the Chinese EV type-approval framework alongside GB 38031 and the GB/T 31467 series.
Published by: Standardization Administration of China (SAC)
Current edition: GB/T 38661-2020
Status: Recommended (GB/T prefix) — widely referenced for MIIT vehicle type approval
Companion standard: GB/T 39086-2020 covers functional safety requirements for BMS (ISO 26262-aligned)
Scope
GB/T 38661-2020 applies to battery management systems installed in all road electric vehicles sold in China, including BEVs, PHEVs, HEVs, and fuel-cell electric vehicles where a secondary traction battery BMS is present.
Operating Environment Requirements
- Operating temperature: -20°C to +65°C (or agreed between vehicle and BMS manufacturer)
- Storage temperature: -40°C to +85°C
- Operating humidity: 5% to 95% relative humidity, non-condensing
- Supply voltage: for passenger cars, 9 V to 16 V DC supply from vehicle 12 V auxiliary bus
Mandatory BMS Functions
- Protection functions: the BMS shall prevent overcharge, over-discharge, overcurrent, and over-temperature of battery cells and the system; protection thresholds and response times are specified
- State estimation: SOC (state of charge) estimation is mandatory; SOP (state of power) estimation and cell balancing are recommended
- Monitoring and measurement: continuous monitoring of total pack voltage, individual cell voltages, module voltages, pack current, and internal temperature at representative points
- Fault diagnosis: the BMS shall detect, classify, and record faults; fault codes and severity classification requirements are defined
- Communication: standardised communication with the vehicle network (typically CAN bus) covering defined message IDs, signal scaling, and transmission rates for state data and fault information
- Data recording: the BMS shall log key event data (fault events, extreme values reached) in non-volatile memory accessible for service purposes
Thermal Runaway Early Warning
GB/T 38661-2020 includes requirements for the BMS to detect early indicators of thermal runaway within cells and issue a warning signal to the vehicle control system with sufficient time for occupants to exit. This requirement aligns with and supports the 5-minute alert mandate in GB 38031-2020 and the more stringent 2-hour no-fire requirement in GB 38031-2025.
Related Standards
- GB 38031 — EV traction battery safety; the BMS is tested as part of the pack system under GB 38031
- GB/T 39086-2020 — Functional safety requirements for EV BMS (ASIL assessment, safety goals, ISO 26262 framework)
- ISO 15118 — Vehicle to grid communication; the BMS communicates charging state data via this protocol
Disclaimer: This is not a definitive guide, just an indication and it is important that you always go back to the source for legislation.
References
- GB/T 38661-2020 Standard details, Code of China
- China Advances National Standards for Electric Vehicle Battery Technologies, MPR China Certification