With the popularization of the concept of new energy, new energy vehicles have gradually entered millions of households. New energy vehicles, as a new car purchase option for ordinary people, have begun to invade the market that originally belonged to traditional fuel vehicles.
When it comes to the core key of traditional fuel vehicles, it is naturally inseparable from the so-called "three major pieces": engine, chassis and gearbox. In new energy electric vehicles, there are also commonly known "three major parts": battery, motor and electronic control. This article focuses on introducing the electronic control of the "three major parts" of new energy electric vehicles (commonly called the battery management system in the industry). BMS).
The biggest difference between new energy electric vehicles and traditional fuel vehicles is that they use power lithium-ion batteries as power drives. As an important link between battery packs, vehicle systems, and motors, the importance of the battery management system BMS is self-evident. Energy car companies regard the battery management system as the company’s core technology. The most famous example is Tesla, which everyone is familiar with. Among the “three major pieces” of Tesla’s electric vehicles, the battery comes from Panasonic and the motor comes from Suppliers, and only the battery management system is the core technology independently developed by Tesla. Most of the core intellectual property rights that Tesla applied for from 2008 to 2015 are related to the battery management system. This shows that the battery management system is related to new energy vehicles. The importance of. In China, the R&D and production of battery management system BMS are mainly concentrated in these three types of companies:
1. New energy vehicle manufacturer, representative company: BYD
2. Battery PACK manufacturer, representative company: Junlee, Pride
3. Professional BMS manufacturer, representative company: Huizhou Yineng, Shenzhen Guoxin Power
What is the purpose of the battery management system BMS?
The battery management system BMS is a new product born in this century. Because the electrochemical reaction is difficult to control and the material performance changes in this process are elusive, it is necessary for such a housekeeper to constantly supervise and adjust the behavior of the battery pack. To ensure safe use, its important functions are:
1. Accurately estimate the state of charge of the power lithium-ion battery pack
Accurately estimate the state of charge (StateofCharge, or SOC) of the power lithium-ion battery pack, that is, the remaining battery capacity, to ensure that the SOC is maintained within a reasonable range, and to prevent damage to the battery due to overcharge or overdischarge, so as to predict hybrid power at any time How much energy is left in the car's energy storage battery or the state of charge of the energy storage battery.
2. Dynamically monitor the working status of the power lithium-ion battery pack
In the process of battery charging and discharging, the terminal voltage and temperature of each battery in the power lithium-ion battery pack, the charging and discharging current and the total voltage of the battery pack are collected in real time to prevent the battery from being overcharged or overdischarged. At the same time, the battery status can be given in time, the problematic battery can be selected, the reliability and efficiency of the entire battery group can be maintained, and the realization of the remaining power estimation model becomes possible. In addition, it is necessary to establish a history file of each battery in order to further optimize and develop supply data for new types of electricity, chargers, motors, etc., and to provide a basis for offline analysis of system failures.
3. Balance between single cells
That is, the single battery is charged in a balanced manner, so that each battery in the battery pack reaches a balanced and consistent state. Equalization technology is the key technology of a battery energy management system that is currently being researched and developed in the world.
What are the characteristics of the technologically advanced BMS currently on the market?
Advanced technology and stable and reliable products will be the core features of future BMS products. So what kind of products are technologically advanced, stable and reliable products? Because the BMS standards of major domestic companies have not yet unified, so Shenzhen Guoxin Power’s BMS Take performance characteristics as an example, from the four dimensions of technology, function, quality, and standard specifications.
Advanced technology:
1. The company masters the core algorithm of battery SOC;
2. Master the state of health estimation, the maximum allowable instantaneous (5s/30s) and continuous charge and discharge power estimation;
3. Master efficient equalization management technology, advanced heat dissipation mechanism, and can support a maximum passive equalization current of 200mA;
4. Master the industry's leading high-precision measurement technology, the total flow and total pressure accuracy can reach 0.5% FSR;
5. Optional multi-function data logger, supporting cloud platform functions such as wireless transmission, large-capacity storage, GPS, etc.;
6. Optional active equalization module, the maximum equalization current can reach 5A, single board 24 strings can be flexibly selected;
Safe features:
1. Battery safety management: reliable overcharge/overdischarge protection, overcurrent/overtemperature/low temperature protection, multi-level fault diagnosis protection;
2. High-voltage safety management: with high-voltage relay adhesion detection, high-voltage interlock detection with high anti-interference, and advanced high-voltage insulation monitoring;
3. With voltage and temperature collection line disconnection diagnosis function;
4. The battery voltage acquisition module has safety mechanisms such as loop overcurrent and short circuit protection, and the circuit is more reliable;
5. With 5~36 series, 5~48 series integrated machine flexible configuration, suitable for all kinds of mainstream methods in the industry;
Stable quality:
1. All components are selected with automotive-grade components, with a high standard operating temperature range of -40°C to 85°C;
2. Wider and more reliable temperature monitoring, the monitoring range can reach -40~125℃;
Comply with standard specifications:
1. Support charging national standards GBT20234-2015 and GBT27930-2015;
2. Support the requirements of product functional safety life cycle management in the ISO26262 international safety standard;
3. Support CCP calibration protocol, UDS, OBD-ii diagnostic protocol.
The Dilemma of Battery Management System BMS
The development of new energy vehicles has not been smooth sailing. In the past two years, with the large-scale promotion and use of new energy vehicles, we have also heard a lot of scandals about new energy vehicles: spontaneous combustion, false cruising range, etc., but why? What about these usage problems? Not using battery management system or using inferior immature battery management system is the main reason. In fact, the safety of new energy vehicles has always been one of the key tasks of the government and the automobile industry.
There are many reasons for the spontaneous combustion of electric vehicles, and it is not possible to sit back and relax after installing a battery management system. For example, in terms of safety, accuracy, life, discharge capacity, etc., a single battery can be charged and discharged 2000 times, and may only be 1000 times after forming a battery pack. If equipped with immature BMS, the battery charging and discharging status cannot be accurately monitored in real time, which can easily cause excessive local power consumption of the battery core, local heat, and information cannot be transmitted to the driver, which can easily lead to battery spontaneous combustion. Industry insiders believe that installing an excellent battery management BMS can effectively improve battery utilization, prevent battery overcharge and overdischarge, and extend battery life, monitor the battery pack and the operating status of each battery cell, and effectively prevent batteries In case of spontaneous combustion, the driver will be warned of emergencies in advance in case of an emergency, so as to gain time for safety.
The future of new energy vehicles and battery management systems
The new energy automobile industry began in the early 21st century, and it has only been developed for more than ten years. Due to people’s desire for environmental protection and renewable energy, new energy vehicles have ushered in development opportunities. In the future, new energy vehicles will act as a challenger to invade the vast market that originally belonged to traditional fuel vehicles, and due to the needs of social development, this kind of market share infringement can be expected.
While looking forward to the rapid development of new energy vehicles, we must clearly recognize that the development of technology is the basis for the development of the industry, and stable, efficient, safe, and reliable products are the embodiment of technology. We must understand that the current domestic The new energy vehicle industry is not friendly. Frequent electric vehicle spontaneous combustion incidents and false cruising range have exposed the imperfections of the current domestic design, testing, and production standards for new energy battery packs and battery management systems.
There are currently hundreds of BMS companies, and large new energy vehicle manufacturers either choose to develop their own battery management systems or use internationally competitive BMS production companies headed by Germany, Japan and the United States.
The lack of technical parameters and standards, and there is no authoritative organization to conduct authoritative testing of the BMS produced by manufacturers. This is the current dilemma of the domestic BMS market, resulting in uneven BMS products, which are difficult to promote on a large scale. At the same time, many automobile manufacturers and battery PAC companies have insufficient understanding of the importance of BMS, thinking that as long as each single battery cell can be connected, the operation of the vehicle can be guaranteed. Low prices, in order to sign the contract, some bad BMS suppliers can only reduce the BMS function index or simply part of the function, thereby planting hidden safety hazards, which is also irresponsible and harmful to the entire industry. Only by establishing a unified industry standard as soon as possible, suppressing manufacturers that do not meet market requirements, and establishing a sound inspection system, can battery management systems and new energy vehicles have a sustainable future. This is also the demand of many manufacturers and consumers.