Functions, Working Principles & Best Practices

As high-voltage lithium battery systems continue to dominate applications such as UPS backup power, data centers, and energy storage systems (ESS), the importance of a reliable control system becomes critical.

The SBMS (System Battery Management System) acts as the “brain” of the battery system — responsible for safety, performance optimization, and communication.

At EverExceed, our high-voltage LiFePO₄ battery systems integrate advanced SBMS technology to ensure maximum safety, intelligent control, and long-term operational stability.

1. Core Functions of SBMS

The SBMS operates through three essential layers:
Sensing – Protection – Management

1.1 High-Precision Data Acquisition & Monitoring

The SBMS continuously collects real-time data across the entire battery system:

• Cell Voltage Monitoring (high accuracy up to ±5mV)
• Total Voltage & Current Detection (±1% accuracy)
• Multi-Point Temperature Monitoring (±1°C accuracy)

To ensure safety in high-voltage battery systems, isolated sampling technologies such as:

• Isolation amplifiers
• Optical relays

are used to prevent electrical hazards.

1.2 State Estimation (SOC / SOH / SOP)

SBMS calculates key battery parameters:

• SOC (State of Charge) – Remaining battery capacity
• SOH (State of Health) – Battery aging condition
• SOP (State of Power) – Maximum available charge/discharge power

Using advanced algorithms such as:

• Coulomb counting
• Kalman filtering

SOP is especially critical in UPS lithium battery systems, as it determines how much power the system can safely deliver to the load.

1.3 Comprehensive Safety Protection

Safety is the top priority in any high-voltage lithium battery solution.

SBMS provides multi-layer protection:

• Overvoltage / Undervoltage
• Overcurrent / Short circuit
• Overtemperature / Low temperature
• Insulation resistance detection (mandatory for high-voltage systems)

When a fault is detected:

• SBMS immediately triggers contactor disconnection
• Sends fault codes to upper systems
• Classifies faults into warning / primary / critical levels

1.4 Cell Balancing Management

To ensure long-term performance, SBMS maintains cell consistency:

• Passive Balancing (resistor-based, widely used)
• Active Balancing (energy transfer, higher efficiency)

Balancing prevents the “weakest cell effect” and significantly extends the lifespan of high-voltage battery packs.

1.5 Thermal Management Control

Temperature directly affects battery safety and lifespan.

SBMS controls:

• Cooling fans
• Heating films
• Liquid cooling systems

Maintaining optimal temperature range:
15°C – 35°C

• Low temperature → Lithium plating risk
• High temperature → Accelerated degradation

1.6 Contactor Control & Pre-Charge Logic

A critical function in high-voltage energy storage systems:

• Controls main positive/negative and pre-charge contactors
• Detects contactor failure (e.g., welding or failure to close)

Pre-charge process:

• Gradually charges inverter capacitors via resistor
• Prevents high inrush current damage

1.7 Communication & Data Logging

SBMS acts as the communication hub:

• Internal Communication:
  • With RBMS or acquisition units via CAN / SPI
• External Communication:
  • With PCS / inverter / EMS
  • Protocols: CAN (CANopen / SAE J1939), Modbus, Ethernet
• Black Box Function:
  • Stores critical fault data for analysis

At EverExceed, our SBMS ensures seamless integration with global inverter brands, improving compatibility and system reliability.

2. How to Properly Use SBMS in High-Voltage Systems

Correct implementation is essential for safe operation.

Step 1: Installation & Wiring (Safety First)

• Use insulated high-voltage sampling wires
• Ensure correct polarity (critical)
• Provide independent low-voltage power supply (12V/24V)
• Install temperature sensors tightly on cells
• Properly connect insulation detection lines

Step 2: Parameter Configuration (The Key Step)

SBMS must be configured based on battery specifications:

• Number of cells (series count)
• Battery capacity
• Voltage & temperature limits
• Current sensor range
• Protection thresholds

Important:
Communication protocol must match the inverter (e.g., CAN protocols)

Step 3: High-Voltage Power-Up Sequence

The SBMS manages a strict startup process:

1. Low-voltage system power-on → self-check
2. Insulation detection
3. Pre-charge stage
4. Main contactor closing
5. System fully operational

This sequence ensures safe startup in high-voltage UPS battery systems.

Step 4: Monitoring & Maintenance

• Real-time monitoring via software
• Analyze historical fault data
• Perform firmware (OTA) updates

3. Three Critical Safety Rules

When operating high-voltage lithium battery systems, these are non-negotiable:

1. Communication Protocol Must Match

Mismatch between SBMS and inverter can lead to:

• System failure
• Overcharge or over-discharge risks

2. Contactor Weld Detection is Essential

Failure to detect welded contactors may cause:

• Short circuits during startup
• Severe system damage

3. Insulation Detection Must Never Be Disabled

In systems above 60V:

• Electric shock risk is fatal
• Insulation monitoring is mandatory

4. Conclusion

The SBMS is a highly integrated system combining:

• Precision measurement
• Intelligent control
• Power management
• Communication coordination

It ensures that high-voltage lithium battery systems operate:

✔ Safely
✔ Efficiently
✔ Reliably

Why Choose EverExceed High-Voltage Lithium Battery Systems?

EverExceed delivers advanced high-voltage LiFePO₄ battery solutions featuring:

• Intelligent SBMS & RBMS architecture
• Multi-layer safety protection
• Strong compatibility with global PCS/inverters
• Proven reliability in UPS, data centers, and energy storage applications