How Lithium Battery BMS Ensures Safety & Prevents Explosions
Lithium-ion battery management system (BMS) ensures safe battery operation through multi-level safety mechanisms to prevent explosion and thermal runaway. The following are its core functions and realization principles:
I. Real-time monitoring and parameter protection
The BMS ensures that the battery operates within safe limits by continuously monitoring key parameters such as voltage, current and temperature:
1.Voltage monitoring
- Real-time monitoring of monomer voltage to prevent over-voltage (>4.2V) or under-voltage (<3.0V). For example, the BMS forcibly cuts off the charging circuit when the unit voltage exceeds 3.75V (level 1 overcharge) or 3.90V (level 2 overcharge).
- Equalization management techniques (passive/active) to reduce individual voltage differences and avoid localized overcharging or overdischarging due to voltage inconsistencies
2.Current Limit
- Sets charge/discharge current thresholds (e.g., 1.0C for charge overcurrent warning, 2.0C for discharge overcurrent) and cuts off the circuit when the limits are exceeded
- Short-circuit protection cuts off the current within milliseconds through MOS tubes to prevent thermal runaway caused by high current.
3. Temperature Management
- Temperature sensor monitors the battery temperature in real time, the working range is usually -20℃~60℃. The temperature sensor monitors the battery temperature in real time, the operating range is usually -20℃~60℃.
- Abnormal temperature (e.g. >60℃) triggers power down or shutdown to prevent electrolyte decomposition and thermal runaway
II. Multi-level protection mechanisms
The BMS utilizes a layered protection strategy with gradual escalation to address risks:
1.overcharge protection
- The charging voltage is divided into three levels of response: termination of charging when it reaches 3.65V; forced cut-off at 3.75V; locking the system at 3.90V until manual intervention.
- Voltage equalization to avoid overcharging of individual cells, e.g. passive equalization through resistive energy dissipation, active equalization to transfer energy to low voltage cells
2.overdischarge protection
- Terminate the discharge when the discharge voltage is lower than 2.5V; in extreme cases (e.g., 2.0V), forcibly cut off and activate the recharging mechanism.
- Avoid dissolution of negative electrode copper foil and growth of lithium dendrites, prevent internal short circuit
3.Overcurrent and short circuit protection
- Dynamically adjustable current thresholds combined with dual hardware (fuse) and software (MOS tube control) protection.
- The BMS cuts off the circuit within 100ms in case of short circuit, suppressing the impact of instantaneous high current (e.g. thousands of amperes) on the battery.
III. Thermal runaway prevention and troubleshooting
1.Thermal runaway warning
- Risk of thermal runaway, e.g. gas pressure surges before electrolyte decomposition, is predicted by monitoring the rate of change of temperature and voltage (dV/dt).
- Combined with historical data analysis, it triggers heat dissipation or isolation of faulty modules in advance.
2.Troubleshooting and Emergency Response
- The BMS records the type of fault (e.g., excessive differential pressure in a single unit, low SOC) and handles it in a hierarchical manner: alarm, power reduction, contactor cut-off
- Disconnection of the main circuit in case of serious malfunction (e.g. thermal runaway) and reporting to an external system via the communication interface
IV. Targeted protection against the causes of explosions
The three main triggers of lithium-ion battery explosions (mechanical abuse, electrical abuse, and thermal abuse) are all mitigated by the BMS:
1.Electrical Abuse Protection
- Electrical abuse such as overcharging, overdischarging, and high currents are major risks, and the BMS directly blocks such paths through voltage/current limiting and equalization management
2.Thermal abuse protection
- Temperature control module prevents localized overheating, inhibits SEI film decomposition and diaphragm melting, and avoids internal short circuits.
3.Indirect protection against mechanical abuse
- Although it cannot directly prevent collisions, the BMS can quickly isolate faulty batteries after mechanical damage, preventing chain reactions
V. System-level security design
1.Redundant protection
- Combination of primary protection (restorable) and secondary protection (irreversible, e.g., fuses) for improved fault tolerance
- Multi-sensor cross validation to reduce false alarms and omissions
2.Data-Driven Optimization
- Records data such as charge/discharge history and temperature distribution for optimizing charging strategies and predicting battery life.
- Protection thresholds are dynamically adjusted to adapt to battery aging through SOC/SOH estimation (e.g., Kalman filtering method) 27 51 .