BMS stands for Battery Management System. It is used for real-time monitoring of battery parameters, fault diagnosis, SOC estimation, driving range estimation, short circuit protection, leakage monitoring, display and alarm, and charging and discharging mode selection.
Since a battery cell is an electrochemical process, multiple cells make up a battery. Each cell has its own characteristics. No matter how precise the manufacturing process is, with the use time and environment, each cell will have errors and inconsistencies. Therefore, the battery management system evaluates the current state of the battery through a limited set of parameters.
In terms of applications, BMS (Battery Management System) can be broadly categorized into two types: one for new energy vehicles and the other for energy storage. This article will primarily focus on the uses of BMS when applied to new energy vehicles.
Real-time tracking of battery operating status and parameter monitoring: Real-time acquisition of battery charging and discharging status data, including total battery voltage, total battery current, temperature at each battery measurement point within the battery pack, and individual module battery voltage. Since power batteries are connected in series, real-time, rapid, and accurate measurement of these parameters is fundamental to the normal operation of the battery management system.
Estimation Functions: The BMS estimation function has four main aspects: First, SOC (State of Charge), a core control algorithm of the BMS, represents the current remaining capacity status; second, SOP (State of Power), which mainly obtains the current battery's available charge and discharge power by looking up a table based on temperature and SOC, and the VCU determines how the vehicle should use the battery based on the power value sent; third, SOH (State of Health), which mainly represents the current battery health status, a value between 0-100%, and is generally considered unusable when below 80%; fourth, SOE (State of Energy), which is mainly used for estimating the remaining driving range. Currently, few domestic manufacturers have developed this algorithm, or they use a simpler algorithm, looking up a table to obtain the ratio of remaining energy to maximum usable energy in the current state.
Charge and discharge control: The system controls the charging and discharging of the battery according to its state of charge. When a parameter exceeds the standard, such as the voltage of a single cell being too high or too low, the system will disconnect the relay to stop the energy supply and release of the battery in order to ensure the normal use and performance of the battery pack.
Fault Diagnosis: Different fault levels are categorized based on the battery's performance, and the BMS and VCU will take different actions depending on the fault level, including warnings, power limiting, or direct high-voltage disconnection. Faults include data acquisition and reliability issues, electrical faults (sensors and actuators), communication faults, and battery status faults.
Thermal management: Real-time temperature monitoring of batteries in each battery compartment, and control of cooling fans to prevent overheating of batteries.
Balance control: The balance function is designed to eliminate inconsistencies between individual battery cells during battery use. According to the barrel effect, during charging and discharging, the worst-performing cell reaches the cutoff condition first, while other cells still have some capacity that has not been released, resulting in battery waste.
