18650 battery 4800mah.About the design of electric vehicle battery management systems

　　As energy shortages, oil prices rise, and urban environmental pollution become increasingly serious, the development and utilization of new energy sources that can replace oil are increasingly valued by governments around the world. In the new energy system, the battery system is an indispensable and important component. In recent years, electric bicycles, hybrid vehicles, electric vehicles, fuel cell vehicles, etc. powered by lithium batteries have received increasing attention from the market. The application of power batteries in the transportation field is of great significance for reducing greenhouse gas emissions, reducing air pollution, and applying new energy. Among them, lithium batteries have attracted more and more attention due to their high energy density, high number of recycles, light weight, and green environmental protection. Therefore, they have been widely used in portable handheld devices such as mobile phones, laptops, and power tools, and have been widely used in portable handheld devices such as mobile phones, laptops, and power tools. It has begun to enter high-power applications such as electric vehicles and electric vehicles, and has become a hot spot in the development of global electric vehicles. However, due to abuse conditions such as heating, overcharge/overdischarge current, vibration, and extrusion of lithium batteries, the battery life may be shortened. Damage, and even fire, explosion and other incidents may occur. Therefore, safety issues have become the main constraints for the commercial promotion of power lithium batteries. Safety standards, safety evaluation methods, safety and reliability control of the battery manufacturing process, and improvement of battery safety and reliability through the optimization of positive and negative electrode materials, electrolytes and separators are the key to ensuring large-scale power supply for safe, low-cost, long-life lithium-ion batteries. Lithium-ion batteries are safe, reliable and the key to practical use. As the core component of battery protection and management, the battery management system must not only ensure the safe and reliable use of the battery, but also give full play to the battery's capabilities and extend its service life. As a bridge between the battery, the vehicle management system, and the driver, the battery management system plays an increasingly critical role in the performance of electric vehicles. The main functions of the battery management system The battery management system is closely integrated with the power battery of electric vehicles. It monitors the voltage, current, and temperature of the battery at all times. It also performs leakage detection, thermal management, battery balance management, alarm reminders, and calculation of residual power. Capacity, discharge power, report SOC & SOH status, and also use algorithms to control the maximum output power according to the voltage, current and temperature of the battery to obtain the maximum mileage, and use algorithms to control the charger for optimal current charging, through the CAN bus interface and vehicle total control devices, motor controllers, energy control systems, vehicle display systems, etc. for real-time communication. Figure 1 is a simple block diagram of the battery management system. The basic functions of the battery management system: 1) Monitor the working conditions of individual cells, such as individual cell voltage, operating current, ambient temperature, etc. 2) Protect the battery to avoid shortened battery life, damage, or even explosions, fires and other accidents endangering personal safety when the battery is working under extreme conditions. Generally speaking, the battery management system must have the following circuit protection functions: over-voltage and under-voltage protection, over-current and short-circuit protection, over-temperature and under-temperature protection, and multiple protection for the battery to improve the reliability of the protection and management system (hardware The protection of execution has high reliability, the protection of software execution has higher flexibility, and the protection of failure of key components of the management system provides users with the third level of protection). These features meet the needs of most mobile phone battery, power tool and e-bike applications. Electric vehicles pose higher challenges to the battery management system. The battery integration system of electric vehicles is an open power system. It communicates through the automotive-grade CAN bus and works together with the vehicle management system, charger, and motor controller to meet the people-oriented requirements of the vehicle. Safe driving concept. Therefore, the automotive-grade battery management system must meet the requirements of TS16949 and automotive electronics, achieve high-speed data collection 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 collection of information such as battery voltage and temperature; achieving high-efficiency balance of the battery, giving full play to the capacity of the battery integrated system to increase the life of the battery integrated system, while reducing heat generation; battery health and remaining power estimation and display; highly reliable communication protocol (automotive-grade CAN communication network); powertrain technology must ensure that the battery's potential is fully utilized, ensuring battery performance and improving battery life under the premise of any safe use of the battery; battery Temperature and heat dissipation management ensure that the battery system operates in a relatively stable temperature environment; leakage detection and complex ground wire design. Since the distribution environment of batteries in electric vehicles is very complex and operates under high voltage and high power, the requirements for EMI/EMC are very high, which brings greater challenges to the design of battery management systems. Hierarchical and modular design of electric vehicle battery systems. Since the electric vehicle battery system is integrated with hundreds or thousands of battery cells, taking into account the space, weight distribution and safety requirements of the car, these battery cells are divided into standard The battery modules are distributed in different locations on the car chassis and are managed uniformly by the powertrain and central processing unit; each standard battery module also has multiple cells connected in parallel and series, and is managed by the module's electronic control unit. The CAN bus reports battery module information to the central processor and powertrain unit. After processing this information, the central processor and powertrain unit provide the final information about the integrated system such as remaining power, health status and battery status. Capability-related information is reported to the vehicle management system through the CAN bus. The hierarchical and modular design of the electric vehicle battery system requires the hierarchical and modular design of the battery management system.

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