Analysis of energy storage BMS and electric vehicle BMS
In the power storage and electric vehicle industries, lithium batteries have become the mainstream application of the industry with their advantages such as high energy density and long cycle life. As the "brain" of the battery, BMS has functions such as voltage, current, temperature monitoring, SOC/SOE state management and control, which can effectively avoid overcharging and overdischarging of the battery and extend the battery life. It is the focus of the industry chain.
What are the differences between energy storage BMS and automotive BMS? We mainly focus on data acquisition, balancing, electrical adaptability and other projects.
● Data acquisition
Data acquisition is the basic function of energy storage BMS and electric vehicle BMS. Both need to realize the collection and monitoring of single cell voltage, temperature, total voltage, total current, state (SOC/SOE) and other data.
The main difference between the two lies in the acquisition error, test method, etc. In fact, as electric vehicles and energy storage power stations have higher and higher requirements for the accuracy of battery cell state management, the accuracy of BMS single cell voltage measurement is basically higher than 3mV, and some are even as high as 1mV. Taking total voltage measurement as an example, since electric vehicles currently use a 400V/800V platform, and the voltage level of power energy storage is generally 1000V/1500V, there are certain differences between the two in terms of measurement range, test equipment, and test methods.
● Balance testing
Balance is the core function of BMS. Since the energy storage system has the characteristics of deep charging and discharging, the consistency of the cell capacity directly affects the efficiency of the energy storage system. Therefore, in order to ensure the consistency of the single cell in the battery pack, the BMS must have the ability to manage battery balance. The energy storage system generally supports active and passive balancing technologies, with a maximum balancing current of 5A to ensure that the available capacity of the battery system is maximized. Electric vehicle BMS generally uses passive balancing, and the balancing current is generally in the hundreds of mA level. As the voltage level and battery pack capacity of new energy vehicles become larger and larger, active balancing may also become one of the development trends of electric vehicle BMS in the future.
● Insulation resistance detection
Both energy storage BMS and electric vehicle BMS should have the function of battery cluster/battery pack insulation resistance detection. The two are similar in test methods, but there will be certain differences in test range and test error.
● Electrical adaptability
The electrical test of electric vehicle BMS mainly refers to GB/T 28046, with a total of 7 test items, including DC power supply voltage, overvoltage, superimposed AC voltage, power supply voltage slow drop and rise, and transient change of power supply voltage; the electrical test items of energy storage BMS are relatively few, including DC power supply range, overvoltage, reverse voltage, and communication short circuit.
● Others
In addition to the above-mentioned differences in electrical performance, energy storage BMS and electric vehicles also differ in other aspects such as electromagnetic compatibility and environmental adaptability. The batteries that energy storage BMS needs to manage are at the MWh or even MWh level, so there are more requirements for electromagnetic compatibility performance testing; while the driving and operating conditions of electric vehicle BMS are more complex, so it requires higher adaptability to various environmental factors.