【Introduction】In recent years, driven by the rapid development of emerging technologies such as the Internet of Things, artificial intelligence, and new energy, unprecedented changes have taken place in the automotive industry. According to statistics, with the continuous improvement of automobile intelligence, the sales volume of automobile complaints has shown a step-by-step growth trend since 2017, and the accompanying safety hazards have also emerged one after another. According to statistics, there will be about 3,000 new energy vehicle fire accidents nationwide in 2021. The increase in the failure rate of automobiles, especially the increase in the spontaneous combustion of new energy vehicles, makes us have to re-examine automobile safety issues in the era of intelligence. As one of the core functions of new energy electric vehicles, BMS (Battery Management System) also plays a particularly important role in the safety of new energy vehicles.
New energy vehicle BMS
As people pay more and more attention to the battery life and battery safety of new energy vehicles, the function of BMS has also been redefined.
System architecture diagram of BMS
Battery, motor and Electronic control technology are the core technologies of new energy vehicles, and the core function of electronic control is BMS (Battery Management System), that is, battery management system. As a pillar behind intelligent driving, BMS protects the safe use of electric vehicle power batteries. BMS is a system that monitors and manages batteries. By collecting and calculating parameters such as voltage, current, temperature, and SOC (state of charge), it controls the charging and discharging process of the battery to protect the battery and improve the overall performance of the battery. The management system also records important logs in real time. It can not only upload to the monitoring center through the Internet of Vehicles, monitor and manage vehicles in real time, but also investigate and locate problems and optimize product design in the later stage. All of these are inseparable from a high-precision and high-reliability RTC chip to improve the accurate timestamp for the BMS log log.
The role of RTC in BMS:
● As one of the wake-up sources, trigger the BMS to perform self-check management on its own working mode (sleep, running…);
● As a condition of the SOC algorithm, it is used to periodically correct the SOC;
● Calendar time, providing BMS with time coordinates (timestamp) corresponding to historical data and fault information.
1. Wake up “physical examination” regularly
The BMS controller needs a real-time clock circuit for timing reminders. When the set time is reached, the RTC will output an alarm wake-up signal (INT interrupt signal) to wake up the controller to perform self-checking actions.
2. A condition of the SOC algorithm for regular SOC corrections
After the system is powered on, read the total voltage of the battery, and then determine an initial power value. Although there is a certain error, this value can basically be used to participate in the subsequent ampere-hour integration calculation. However, in special scenarios, for example, the battery has not been left to stand for more than 2 hours, and the system restarts due to some problem during high-power discharge. At this time, there will be a problem with the open-circuit voltage method to determine the power. In order to solve this problem, it is necessary to design an external independent RTC to record the SOC and related information in real time. After the system starts, read the SOC log in the flash, and then judge whether the time when it is stored has passed 2 hours, so as to determine whether it is Use the open circuit voltage method to determine the initial SOC, or directly use the SOC value stored in the FLASH as the initial SOC.
3. Calendar time, providing BMS with time coordinates (timestamp) corresponding to historical data and fault information
BMS will record important logs in real time according to the time provided by RTC. It can not only upload to the monitoring center through the Internet of Vehicles, monitor and manage vehicles in real time, but also investigate and locate problems and optimize product design in the later stage.
Dapu Communications has launched a series of high-precision, high-reliability integrated RTCs, which provide reliable time stamping and timing functions for the stable operation of the BMS system, and help users perform fault analysis and risk management of battery packs.
Dapu RTC features:
● Built-in crystal
Reduce the number of components in the design scheme, improve the PCB layout efficiency, and reduce the system failure rate.
● High precision: ±3.4ppm/±5ppm/±[email protected]℃~+85℃
Provide accurate timestamps for logs to help customers pinpoint problems.
● Low power consumption: as low as 0.5uA
Improve battery life.
● Support backup battery switching
Cope with the main power failure and further improve the system reliability.
● Ultra-small package: 3.2*2.5*1.0mm
It is suitable for system miniaturization and high-density design, and gets rid of the constraints of traditional solutions.
Typical application block diagram of Dapu RTC
With the rapid technological development, great changes are taking place in every field, and the market puts forward more stringent requirements for the functional definition, high reliability and more challenges of core chips/devices.
Dapu Communication RTC products adhere to the high-precision and high-reliability technology as the main line, and gradually realize product serialization according to the needs of the industry and customers. So far, 8 major categories and more than 15 single item numbers have been developed, covering a wide range of fields such as communications, automobiles, electric power, medical care, and industrial control. In the future, Dapu will continue to focus on in-depth research and innovation, and strive to meet the diversified needs of the market.