How BMS works

The working principle of BMS (Battery Management System) mainly includes data collection, analysis and processing, control execution and communication transmission. The following is a detailed introduction:

Data collection

Connect to the battery or BMS through various high-precision sensors to collect key parameter information of the battery, including:

Voltage sensor: Accurately measure the voltage value of battery cells or Battery Packs, and promptly detect abnormal voltage conditions such as overcharging and over-discharging.

Current sensor: monitors the battery's charge and discharge current, providing a basis for analyzing the battery's charge and discharge characteristics.

Temperature sensor: Always pay attention to the temperature changes of the battery, because too high or too low battery temperature will affect its performance and life. Accurate temperature monitoring can take heat dissipation or insulation measures in advance.

Analytical Processing

Signal conversion: The collected analog signal data is transmitted to the data acquisition card, which converts it into digital signal for further processing.

Data preprocessing: With the help of professional data processing software and algorithms, the data is filtered, calibrated and other preprocessing operations are performed to remove noise and interference and improve data accuracy.

State estimation: Use specific algorithms to estimate and analyze key parameters of the battery, such as the state of charge (SOC), state of health (SOH), and state of power (SOP). For example, the Kalman filter algorithm combines historical data with currently collected data to continuously optimize the evaluation of the battery state, thereby fully understanding the performance and state of the battery.

Control execution

Charge and discharge control: According to the battery status and preset parameters, the battery charge and discharge process is controlled to prevent overcharge, overdischarge and overcurrent, and protect the safety and life of the battery. For example, when the battery voltage reaches the overcharge voltage threshold, the BMS will cut off the charging circuit in time; when the battery voltage is lower than the overdischarge voltage threshold, the BMS will stop discharging.

Balancing management: Due to the inconsistency of batteries during production and use, BMS will use balancing methods to make the batteries consistent, including passive balancing and active balancing. That is, a pair of thresholds for starting and ending balancing is set. When the difference between the single cell voltage extreme value and the average value of this group of voltages reaches the starting threshold, balancing is started, and when it reaches the ending threshold, balancing is ended.

Thermal management: According to the temperature of the battery, control the heat dissipation or heating device to make the battery work within the appropriate temperature range and improve the efficiency and life of the battery. For example, when the battery temperature is too high, the BMS will start the cooling fan or cooling water pump to dissipate heat; when the battery temperature is too low, the BMS will turn on the heating element for heating.

Communication transmission

Internal communication: In a distributed BMS, the master control unit and the slave control unit perform data transmission and command interaction through communication methods such as CAN bus; in a centralized BMS, each functional module uses intra-board communication to improve communication efficiency and ensure synchronous data collection.

External communication: BMS communicates with the host computer, vehicle controller, charger and other external devices through the communication interface, transmits the battery status information to them, and receives their control instructions. For example, BMS transmits the battery's SOC, SOH and other information to the vehicle controller, and the vehicle controller controls the vehicle's energy management strategy based on this information; BMS communicates with the charger to control and manage the charging process.