Article Source:Li Cheng - Electronic Enthusiast Network
In electric vehicles, the battery is the main core part, and the performance of the battery directly determines the charging speed, vehicle endurance and safety issues. In order to solve these problems, improve battery efficiency and extend battery life, car companies have added BMS technology to electric vehicles to monitor battery data in real time.
What role does BMS play in electric vehicles and its realization form
The BMS system mainly plays a role in the management of battery charging and discharging in electric vehicles. The BMS system can perform battery status analysis, power management, battery information management, battery status monitoring, and battery protection. Through systematic management, the battery can avoid battery overcharging, overdischarging, and overheating, and improve battery performance and service life.
The BMS system is mainly implemented in two forms: centralized and distributed. The centralized BMS collects and monitors battery pack data through a bus. The centralized BMS is divided into a high-voltage area and a low-voltage area. The high-voltage area collects data from single cells, and the low-voltage area mainly integrates power supply and communication lines. The centralized BMS system has the characteristics of low cost and simple topology, and is generally used in low-voltage, small-capacity batteries, such as robots and small two-wheel electric vehicles.
Distributed BMS is modularized and hierarchically managed. Each group of batteries will be matched with the LECU, and data such as voltage and temperature of the battery cells will be collected to determine the state of the battery. The high-voltage area is responsible for monitoring the total voltage of the battery, the total voltage of the bus, and the state of the insulation resistance. The data collected from the LECU and high-pressure zone is analyzed and then entered into the BMU to be summarized and transmitted to the BSE. Ultimately, BSE makes the judgment.
Competition is inevitable under the wind. Electric vehicles are developing rapidly. Many chip manufacturers have launched BMS chips to provide car companies with more choices.
TI high-precision battery monitoring, balance, protector
The rapid development of automobile electrification is irreversible, and the BMS system has become the primary core issue. TI has made great achievements in the field of electric vehicle BMS, and has successively released wired BMS and wireless BMS solutions that comply with the ASIL D standard, leading the industry.
(BQ79614-Q1 circuit topology Source: TI)
BQ79614-Q1 is a high-precision battery monitor, balancer and protector that can be applied to the BMS module of hybrid and pure electric vehicles. It can monitor the battery temperature in real time, and can automatically pause and start in order to avoid overheating. operate. The chip's operating voltage is 12V, which can quickly perform high-precision voltage monitoring for 14 batteries within 128S. The BQ79614-Q1 chip integrates a front-end filter and a post-ADC low-pass filter. The front-end filter is to reduce costs and can use a simple, low-voltage differential RC filter on the battery input circuit. The ADC low-pass filter is to monitor the filtered DC voltage to facilitate the calculation of the state of charge of the battery. The chip can be used to measure the external thermistor BQ79614-Q1 can be connected to the BQ7600 device in communication or directly communicate with the MCU through the UART interface. In the case of an abnormal communication line, the MCU can directly communicate with the battery pack through an isolated differential daisy chain.
ST 14S high-precision, fast-speed battery monitoring and protection chip
STMicroelectronics (ST for short) has led the semiconductor market for many years, with chip applications spanning multiple fields, and has also become a major supplier of automotive chips. In the automotive field, in order to meet market and design needs, we have introduced high-performance, high-efficiency 32-bit automotive-grade MC, high-precision, low-energy VIPower smart switches, multi-channel, high-precision BMS ICs and various protection devices. ST can provide a full range of application products, technical support and solutions in the field of automotive electronics.
(L9963 frame picture source: ST official website)
L9963 is an automotive BMS IC launched by ST. The chip has the characteristics of high precision and high measurement speed. Its accuracy error is only ±2mV. It can read 96 units of data within 4 ms, which is highly recognized in the industry. . The most noteworthy thing in BMS is the accuracy and measurement speed of the IC. The high precision can read the status of each unit more accurately. The high measurement speed solves the main problem of aging, improves the detection accuracy, and reflects the battery status in real time.
L9963 can be used in 48V or higher voltage power grids, and can monitor 4 to 14 battery cells in series and 7 external NTCs. Data transmission is carried out through SPI and isolated interface. On the other hand, 1 to 31 devices can be connected in a daisy chain mode, and the entire data conversion delay is less than 4 microseconds. The communication serial bus bandwidth of the L9963 daisy chain is 2.66 Mbps, which greatly reduces the problem of data sampling delay. Among them, 31 L9963s are connected through the daisy chain, and data reading of 434 units can be completed within 16 milliseconds. The chip also integrates 9 GPIO external communication interfaces to achieve external communication and external monitoring. Redundant circuit function is the characteristic of this chip, and it is also a kind of protection for driving safety. The L9963 redundancy function can cross-check the internal ADCs. When one of the ADCs fails, the nearest ADC will directly take over the failed ADC to avoid driving accidents.
On the basis of L9963, ST has also launched three evaluation boards for use with SPC58 Chorus MCU, realizing that the evaluation board is closer to the final research product and speeding up the research progress of developers.
ADI 12-channel battery monitor
According to the ADI official website, the first integrated high-voltage battery stack monitor was launched as early as 2008, and it has been iteratively updated to the fourth generation, and the fifth-generation product is still in the development stage.
(LTC6811-1 frame drawing source: ADI)
LTC6811-1 is ADI's fourth-generation BMS IC. It is a battery pack monitor that can detect the voltage of up to 12 batteries in series. The measurement accuracy is higher than that of ST L9963, and the total measurement error is less than 1.2mV. Battery detection only requires 290s. LTC6811-1 can connect multiple batteries in series, so the chip can complete real-time battery status monitoring in high-voltage battery strings. The chip also has an ISOSPI interface, which can realize high-speed remote communication with the device. LTC6811-1 can connect 12 groups of batteries through a daisy chain to realize the function of multi-channel communication, monitor the battery status, and perform suspend and start operations according to the current status of the battery. The chip uses an isolated power supply.
To learn more about BMS using LTC68XX chips, click on the link: https://bit.ly/3F2Z2KQ
Summarize
In automobiles, the BMS system is equivalent to the bridge between the vehicle and the kinetic energy management system. The performance of the BMS IC has an impact on the safety, battery life, and mileage of electric vehicles. BMS systems with higher sampling accuracy and faster speed can maximize battery utilization and improve stability and reliability.
