To ensure the safety and reliability of lithium iron phosphate battery packs, it is essential to develop and manufacture a coordinated management system for the battery packs. The battery management system provides an interface for interaction with external systems, such as charging power supplies, switching devices, loads, and data display devices.
A battery pack management system can transform a group of "dumb" battery cells into a smart battery pack.
The rapid development of electric vehicles by automakers and related manufacturers has benefited from the higher performance and more comprehensive functions provided by battery management systems. The management system can be broken down into two sciences: battery monitoring and battery control; the monitoring part includes voltage and temperature measurement and battery balancing. These are the fundamental attributes of a battery management system.
Although lithium iron phosphate batteries remain safe under conditions such as short circuits, overcharging, compression, and puncture, these conditions can significantly impact their cycle life. The manufacturing process for lithium iron phosphate batteries is relatively complex. The consistency variation among individual cells is greater than that of sealed valve-regulated lead-acid batteries. This causes the voltage of some individual cells to rise rapidly during the later stages of charging, and excessive differences can severely affect battery life. To prevent these phenomena, a power management system is needed to ensure the safety and reliability of the battery.
The battery management system (bMS) is a core component for battery pack protection and management. It not only ensures the safe and reliable use of batteries but also maximizes battery performance and extends battery life. As backup power for communication applications, the management system acts as a bridge between the high-voltage DC power supply and the battery. The requirements for the battery pack management system must meet the requirements of the communication power supply system; therefore, the safety management mode of the battery management system is crucial to battery safety. The battery pack management system mainly includes a data acquisition unit, a computing and control unit, a balancing unit, a control execution unit, and a communication unit. The architecture diagram is as follows:
1. Basic uses of battery pack management system
(1) Monitor the working status of individual cells, such as testing the voltage, charging and discharging current, and ambient temperature of the battery pack for each individual cell;
(2) Protect the battery and guard against shortened battery life and battery damage under extreme conditions.
2. Key functions of the battery management system
(1) Overvoltage protection
When the charging voltage of a single battery cell exceeds the permissible value, charging should be stopped immediately, and the charging equipment should be disconnected from the battery pack.
(2) Over-discharge alarm
An alarm will be issued when the discharge voltage of a single battery cell falls below the warning value;
(3) Over-discharge protection
When the discharge voltage of a single battery cell falls below the protection value, the discharge will immediately stop, the connection between the electrical equipment and the battery pack will be disconnected, and an alarm will be triggered.
(4) Overcurrent alarm
An alarm will be issued when the input or output current of the battery pack exceeds the warning value;
(5) Short circuit protection
When a short circuit occurs in the battery pack, immediately stop discharging, disconnect the electrical equipment from the battery pack, and issue an alarm.
(6) Over-temperature alarm
An alarm will be triggered when the battery temperature or ambient temperature exceeds the warning value.
(7) Over-temperature alarm
An alarm will be issued when the battery temperature or ambient temperature exceeds the warning value.
(8) Over-temperature protection
When the ambient temperature or the internal temperature of the battery pack exceeds the protection threshold, the connection between the charging device and the battery pack will be immediately disconnected, accompanied by an alarm. Once the ambient temperature or the internal temperature of the battery pack returns to the permissible value, the battery management function can be manually or automatically restored, without affecting the battery discharge function.
3. Estimate battery pack SOC
SOC (State of Charge) is the remaining charge of the battery. Maintaining SOC within a reasonable range helps prevent damage from overcharging or over-discharging, and it's essential to regularly monitor the battery's remaining capacity.
4. Equalize the individual cells in the battery pack.
Due to the complex manufacturing process of lithium iron phosphate batteries and the relative reactivity of lithium ions, inconsistencies in the voltage of individual cells within the battery pack can occur. Equalizing the charging of individual cells in the battery pack, ensuring they reach a uniform state, can effectively extend the battery pack's lifespan and significantly improve its operational efficiency (this function can be added or removed according to user requirements).
5. Parallel communication
It provides an interface for communication with the base station monitoring system, transmitting and displaying information such as battery pack status, alarms, and SOC, enabling remote monitoring and management intervention.
