Static protection scheme for Battery Management System (BMS)

Scheme Introduction

The full name of BMS is Battery Management System, which stands for Battery Management System. It is a device that cooperates with monitoring the status of energy storage batteries, with the main purpose of intelligent management and maintenance of various battery units, preventing overcharging and overdischarging of batteries, extending the service life of batteries, and monitoring the status of batteries. Its main functions include real-time monitoring of physical parameters such as battery voltage, current, temperature, as well as state parameters such as SOC (remaining charge) and SOH (health status) of the battery, and issuing alarms when abnormalities occur; Adjust the current and voltage for charging and discharging based on the real-time status of the battery, ensuring that the battery operates within an appropriate range and preventing overcharging and overdischarging; Monitor the temperature distribution of the battery pack and adjust the operation of the cooling system as needed to prevent overheating or overcooling of the battery.

Due to its design and structural influence, battery energy storage systems have the characteristics of a large number of batteries, complex systems, harsh operating environments, and high requirements for the anti-interference performance of BMS. In order to ensure the safe, reliable, and efficient use of the battery throughout its entire lifecycle, the energy storage BMS will use TVS to protect the power and signal ports. The series of TVS products launched by Jingxin Micro have excellent protective performance, providing reliable support for the design of BMS.

BMS Overview

BMS， As a key bridge between the electric vehicle battery pack, vehicle architecture, and motor, it is fully responsible for the comprehensive management of the electric system. Its core functions focus on three aspects: data collection, battery status evaluation, and single battery balance adjustment. The data collection work, specifically, involves continuously monitoring the voltage, temperature, charging and discharging current, and total voltage of each battery in the power battery pack, and constructing a detailed data recording system. These data are not only the cornerstone of SOC estimation model construction, but also provide valuable information for the development and optimization of new products such as batteries, chargers, and motors. At the same time, they serve as important references for offline analysis of system faults.

In the field of battery state assessment, the focus is on estimating key indicators such as SOC (state of charge), SOP (power state), and SOH (state of health). The SOC parameter is the basis for estimating the battery state, and the company's core competitiveness lies in the accuracy of SOC estimation. The higher the accuracy, the higher the range for batteries of the same capacity. High precision SOC estimation can effectively reduce the required battery cost.

Single cell batteries have a certain temperature tolerance range. In practical applications, if the volume is too large, it will cause local overheating, which will affect the safety performance of the battery. Therefore, the power battery pack contains a series of connected individual cells. BMS can effectively detect and control inconsistencies between individual batteries by monitoring the working parameters of the power battery in real-time, thereby improving the safety and overall performance of the vehicle. In addition, BMS can prevent overcharging and overdischarging of the power battery by controlling it to operate within the optimal working range, thereby improving battery efficiency, extending its service life, and reducing battery costs.

The BMS system mainly consists of the following parts:

Main control unit (BMU): responsible for controlling the cell level within the battery module, including monitoring cell voltage and temperature signals, balancing control, SOC estimation, battery state of health (SOH) estimation, and thermal management control.

Control Unit (CMU): Responsible for module level control, including system relay control, alarm signal output, and input/output with external devices. It summarizes the status information of all cells in the series connected battery pack and can be displayed through a touch screen or communicate with a PC computer.

Analog Front End (AFE): A component used to collect readings of battery voltage, temperature, and current, typically responsible for physically closer measurements to the battery and controlling circuit breakers to disconnect the battery from the system in the event of a fault.

Communication interface: such as CAN bus, used for data exchange between BMS and external devices to achieve remote monitoring and control.

Application examples

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The MOS transistor in the BMS charging and discharging circuit generates a leakage peak voltage due to the sudden change of current during switching, which damages the MOS transistor. The faster the switching speed of the power transistor, the higher the overvoltage generated. To prevent device damage, high-power TVS diodes will be added at both ends of the power supply. Based on the different battery voltages in BMS, we recommend different models of TVS products, and customers can choose according to their actual situation.