BMS Communication Protocols: Scenario-Based Selection, Customization and Field Deployment for Modern Custom Lithium Battery Applications
Abstract
The rapid expansion of low-voltage and medium-voltage customized lithium battery systems for mobility, robotics and stationary energy storage has made Battery Management System (BMS) communication protocols the core bottleneck of battery system compatibility, operational safety, and intelligent device linkage. As the core interactive carrier between smart lithium batteries and terminal controllers, a BMS monitors cell voltage, temperature, State of Charge (SOC), State of Health (SOH) and multi-level fault status. More importantly, it establishes two-way data interaction and real-time power scheduling with upper controllers, motor drivers and cloud IoT terminals via standardized or customized communication interfaces. This paper systematically classifies mainstream wired and wireless BMS communication protocols, analyzes protocol adaptation logic for mainstream new energy terminal devices including light electric vehicles, smart robots and industrial handling equipment, and proposes actionable industrial deployment guidelines for battery hardware engineers and third-party BMS system integrators.
1. Overview of Mainstream BMS Communication Protocols
Combined with physical layer hardware and application layer specifications, mainstream commercial BMS communication protocols are divided into six categories, with clear hierarchical application boundaries between internal board-level communication and external device interaction:
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UART/TTL (Private Serial Protocol): Low-cost, point-to-point short-distance communication; no unified industry standard; mainly for local debugging, BLE/Wi-Fi wireless transparent transmission. It features low real-time performance and cannot be applied to safety-critical control loops.
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Modbus-RTU over RS485: The most widely adopted low-speed universal industrial protocol with a master-slave polling architecture and CRC16 cyclic redundancy check. It supports a maximum transmission distance of 1200 meters, with standardized register mapping for core battery operating parameters. Featuring low hardware and deployment cost, this protocol is suitable for routine non-emergency battery data monitoring.
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CAN 2.0B / CAN FD: High-reliability differential field bus equipped with multi-node bus arbitration, millisecond-level data transmission and automatic fault withdrawal mechanism. It is the only mainstream commercial protocol that supports battery safety interlock and emergency power cutoff, which is indispensable for high-risk power battery system applications.
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I2C/SMBus: On-board short-distance communication protocol, mainly deployed for internal signal acquisition between BMS main control units and AFE analog front-end chips, completing high-precision single cell voltage and temperature sampling inside battery packs.
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LIN Bus: Low-rate single-wire low-cost bus, limited to auxiliary multi-point temperature signal collection inside integrated battery modules due to poor transmission efficiency.
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Custom Wireless Protocols (BLE/Wi-Fi): UART transparent transmission based wireless communication solution, only applicable for remote data viewing and cloud data reporting. It is prohibited for closed-loop battery safety control under all industrial design specifications.
The core design principle for BMS protocol customization: Configure low-cost Modbus or UART protocol for simple data monitoring scenarios; deploy CAN bus for all application scenarios that require real-time safety protection and dynamic battery power limiting.
2. Scenario-Based BMS Protocol Customization Analysis
This paper classifies all mainstream downstream battery application scenarios into two core categories: consumer micro-mobility with stationary small-scale energy storage, and intelligent robot with industrial automation equipment. Targeted protocol matching and standardized BMS customization schemes are proposed for each scenario based on operating environment and control logic differences.
2.1 Consumer Micro-Mobility, Garden Tools & Residential Small-Scale Energy Storage
This track features low-voltage lithium batteries (12V–72V), replaceable hot-swap battery design, cost-sensitive mass production, and simple system linkage logic, covering electric bicycles, electric scooters, electric motorcycles, cordless garden power tools, and residential household small-capacity energy storage batteries.
Optimal Protocol Matching Scheme: Primary RS485 Modbus-RTU with auxiliary TTL UART and BLE wireless communication
Most light electric mobility devices adopt hot-swappable replaceable lithium battery architecture; downstream terminal manufacturers prioritize low BOM cost and cross-device battery interchange compatibility for mass production. Modbus-RTU with unified public register tables realizes stable plug-and-play battery identification, real-time dashboard SOC display and low-voltage over-discharge protection for light EV terminals. For consumer electric bicycles and high-speed electric motorcycles, customized Modbus address mapping simplifies seamless matching with brushless motor controllers and vehicle central control systems. For cordless lawn mowers, hedge trimmers and other outdoor garden power tool lithium battery packs, simplified private UART serial protocols are widely adopted to reduce BMS board size, cut chip cost and meet small-size portable battery design constraints.
For grid-connected residential small-capacity energy storage batteries, a dual-protocol hardware design is highly recommended for system compatibility and safety. The Modbus-RTU channel undertakes local HMI and energy management system (EMS) data collection, while the reserved CAN interface supports coordinated charge and discharge control with power conversion systems (PCS). It is critical to note that Modbus polling communication has inherent transmission delay; engineers must never configure Modbus protocol to execute over-temperature, over-voltage and other emergency cutoff commands for household energy storage battery systems.
2.2 Intelligent Robot & Industrial Automation Scenarios
This track has strict requirements for communication real-time, anti-interference and multi-node parallel networking, covering humanoid robots, commercial service robots, industrial manipulators, automated production line equipment, multi-specification UAVs, AGV handling carts and golf carts.
Optimal Protocol Matching Scheme: Primary CAN 2.0B/CAN FD with auxiliary Modbus-RTU
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Humanoid & Service Robots: These devices adopt distributed modular multi-battery architecture. CAN FD bus completes synchronous linkage of distributed joint power batteries, dynamic current allocation and personnel safety interlock logic. Low-priority auxiliary parameters such as battery surface temperature are uploaded via Modbus-RTU to reduce CAN bus load and avoid signal congestion.
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Industrial Robots & Factory Automation Equipment: Industrial sites feature severe electromagnetic interference from high-power motors and frequency converters. The differential signal characteristic of CAN bus provides superior anti-interference performance for on-site communication. The BMS transmits battery SOH and historical fault data to PLC upper computers to support equipment condition monitoring and predictive maintenance.
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Civil, Commercial and Industrial-Grade UAVs: High-density series-connected lithium battery packs are widely equipped on multi-specification UAV devices. The SMBus protocol completes high-precision internal single-cell sampling, while customized CAN protocol realizes real-time power limiting interaction with flight controllers. High-altitude commercial and industrial UAVs require redundant dual CAN communication circuits to prevent flight system failure caused by single-channel communication interruption.
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AGV Carts & Golf Carts: As fixed-route shuttle vehicles, AGVs and golf carts require closed-loop vehicle motion control based on CAN bus. The auxiliary Modbus-RTU channel connects to workshop central monitoring platforms for batch statistics and offline analysis of fleet battery operating data.
3. Universal Industrial Deployment & Customization Suggestions
Combined with common on-site communication faults, system compatibility obstacles and mass production constraints in the lithium battery industry, this section summarizes five universal, executable deployment and customization guidelines for BMS protocol development:
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Hierarchical Dual-Protocol Standardization: Deploy a unified dual-channel communication architecture for all customized lithium battery systems. The CAN bus channel is dedicated to safety closed-loop control including overcurrent, overvoltage and thermal runaway protection; Modbus or UART channels are applied to non-critical data collection, equipment debugging and cloud data transmission. This architecture balances system safety performance and whole-machine manufacturing cost.
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Unified Register Specification for Hot-Swap Replaceable Batteries: For interchangeable batteries used in micro-mobility vehicles and portable garden power tools, BMS developers must adopt T/CIAPS0009 industry standard Modbus register mapping. Disordered private register address definition is prohibited to realize cross-brand and cross-device battery plug-and-play compatibility.
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Anti-Interference Optimization for Industrial Scenarios: For BMS deployed on robots and field automation equipment, add matched CAN bus terminal resistors and signal isolation circuits. All RS485 communication cables shall adopt shielded wiring construction to eliminate electromagnetic signal interruption under high-interference industrial working conditions.
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Safety Boundary of Low-Speed Communication Protocols: UART and Modbus-RTU protocols are strictly prohibited from executing thermal runaway alarm and main circuit breaking instructions. All high-power mobile power equipment must complete core battery safety logic judgment and hardware cutoff through CAN bus communication.
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Reserved Protocol Expansion Interface: All customized BMS firmware and hardware circuits shall reserve CAN FD and Modbus TCP expansion ports. This design reserves hardware redundancy for future battery cluster collaborative scheduling and industrial internet platform upper-layer access.
4. Conclusion
With the continuous diversification of customized lithium battery terminal scenarios, BMS communication protocol selection has evolved from a simple technical parameter configuration to a systematic engineering solution that balances manufacturing cost, communication real-time performance, anti-interference capability and cross-device compatibility. Low-power consumer battery scenarios prioritize low-cost Modbus and private UART protocols to control terminal product BOM cost. High-reliability scenarios covering intelligent robots and industrial mobile equipment take CAN bus as the core communication backbone to guarantee system operational safety. Battery and BMS design engineers should formulate differentiated protocol schemes according to terminal application risk levels, rather than adopting universal one-size-fits-all BMS firmware. Scenario-oriented standardized BMS protocol customization will become a key technical barrier and core competitive advantage for downstream lithium battery supporting manufacturers in the new energy industry.
