As the most important function of the entire battery management system (BMS), safety protection is based on the previous four functions. It mainly includes over-current protection, over-charge and over-discharge protection, over-temperature protection, and insulation monitoring.
Due to the internal resistance of the battery, excessive current during battery operation can cause internal heating of the battery, which increases heat accumulation and causes an increase in battery temperature, thereby leading to decreased thermal stability of the battery.
For lithium-ion batteries, the lithium-ion deintercalation capacity of the positive and negative electrode materials is fixed. When the charging and discharging current is greater than their deintercalation capacity, the polarization voltage of the battery will increase, resulting in a decrease in the actual capacity of the battery, affecting the battery life, and in serious cases, affecting the safety of the battery. As a result, the 48v battery management system seeks to manage deintercalation capacity to ensure that batteries are never subjected to current loads that exceed their capacity. The system uses advanced algorithms to monitor charging and discharging activity continually, ensuring that the current flowing through the batteries remains within safe operating limits. Through efficient deintercalation capacity management, the 48v battery management system can minimize the risk of battery damage, promote optimal battery performance, and extend the lifespan of lithium-ion batteries.
In short, the battery management system will determine if the current value exceeds the safe range, and will take corresponding safety protection measures once exceeded.
During the charging process, when the charging voltage exceeds the battery's cut-off charging voltage, the positive electrode crystal structure will be destroyed, causing the battery's capacity to decrease. Moreover, when the voltage is too high, it can cause a short circuit between the positive and negative electrodes and lead to an explosion. Overcharging is strictly prohibited.
The battery management system will detect the voltage of individual cells in the system. When the voltage exceeds the charging limit voltage, the battery management system will disconnect the charging circuit to protect the battery system.
During discharge, if the discharge voltage is lower than the battery cut-off voltage, the metal flow on the negative electrode of the battery will dissolve, causing irreversible damage to the battery. There may be internal shorts or leaks when over-discharged batteries are recharged. When the voltage exceeds the discharge limit voltage, the battery management system will disconnect the discharge circuit to protect the battery system.
For over-temperature protection, it needs to be combined with the thermal management function mentioned above. The battery's activity varies at different temperatures. Long-term exposure to high-temperature environments will reduce the structural stability of the battery material and shorten the battery life. The battery activity is limited at low temperatures, which will cause a decrease in available capacity, especially the charging capacity will become very low, and may also pose safety hazards.
The battery management system can prohibit charging and discharging when the battery temperature exceeds the high-temperature limit or drops below the low-temperature limit. Overall, the battery condition monitoring system that incorporates temperature monitoring and control functions can significantly minimize the impact of temperature on battery health, promote reliable performance, and ensure efficient energy storage.
Insulation monitoring is also one of the important functions to ensure the safety of the battery system. The battery system voltage usually ranges in hundreds of volts. Once leakage occurs, it will pose a danger to personnel, so insulation monitoring is crucial.
The battery management system will monitor the insulation resistance value between the total positive and total negative to the vehicle body, and if the insulation resistance value falls below the safe range, it will report a fault and disconnect the high-voltage electricity.
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