Design of battery management system for electric vehicles
Main functions of battery management system
The battery management system is closely integrated with the power battery of electric vehicles, and it constantly detects the voltage, current, and temperature of the battery. It also performs leakage detection, thermal management, battery balancing management, alarm reminders, calculates the remaining capacity, discharge power, and reports the SOC&SOH status. It also uses algorithms to control the maximum output power according to the voltage, current, and temperature of the battery to obtain the maximum mileage, and uses algorithms to control the charger to charge with the optimal current. It communicates with the vehicle master controller, motor controller, energy control system, vehicle display system, etc. in real time through the CAN bus interface.
Basic functions of the battery management system: 1) Monitor the working conditions of the single cell, such as single cell voltage, working current, ambient temperature, etc. 2) Protect the battery to prevent the battery from shortening its life, damage, or even explosions, fires, and other accidents that endanger personal safety when the battery is working under extreme conditions.
Generally speaking, the battery management system must have the following circuit protection functions: overvoltage and undervoltage protection, overcurrent and short circuit protection, over-temperature and over-temperature protection, and provide multiple protections for the battery to improve the reliability of the protection and management system (hardware-executed protection has high reliability, software-executed protection has higher flexibility, and the protection of key components of the management system provides users with a third level of protection). These functions can meet the needs of most mobile phone batteries, power tools, and electric bicycle applications.
Electric vehicles pose higher challenges to battery management systems
The electric vehicle battery integration system is an open power system that communicates through the automotive-grade CAN bus and works with the vehicle management system, charger, and motor controller to meet the car's people-oriented safe driving concept. Therefore, the automotive-grade battery management system must meet the requirements of TS16949 and automotive electronics, achieve high-speed data acquisition and high reliability, automotive-grade CAN bus communication, high anti-electromagnetic interference capabilities (the highest level of EMI/EMC requirements), and online diagnostic functions.
Its main functions are: high-speed acquisition of information such as battery voltage and temperature; achieving high-efficiency battery balancing, giving full play to the capacity of the battery integrated system to increase the life of the battery integrated system, while reducing heat generation; estimation and display of battery health and remaining power; highly reliable communication protocol (automotive-grade CAN communication network); powertrain technology must ensure that the battery is used safely, give full play to the potential of the battery, ensure battery performance, and increase battery life; battery temperature and heat dissipation management, so that the battery system works in an environment with relatively stable temperature; leakage detection and complex ground wire design.
Because the distribution environment of batteries in electric vehicles is very complex and they are in a high-voltage and high-power working state, the requirements for EMI/EMC are very high, which brings greater challenges to the design of battery management systems.
