The technical core of the battery box: for safe automatic fire extinguishing device

"Safety Technical Conditions for Motor Vehicle Operation" (GB7258) Section 12.10.4 stipulates: "Pure electric passenger cars and plug-in hybrid buses with a length of 6 meters or more shall be able to monitor the working state of the power battery and alarm when abnormal conditions are found. And within 5 minutes after the alarm, the outside of the battery box cannot explode."

The significance of this article is to point out the importance of the early monitoring and early warning technology for the thermal runaway of the new energy vehicle battery box. People in the circle understand that whether it is a lithium iron phosphate battery or a ternary battery, once the thermal runaway diffusion fire occurs, the fire extinguishing is effective. The possibilities are minimal. This article directly refers to the core - the real security is also the very early, accurate and reliable early warning technology, which is also a profound lesson left to us by the new energy vehicle fire and explosion accident.

"General Technical Conditions for Pure Electric City Passenger Cars" (JT/T1026-2016) Article 4.3.2.11 stipulates: "The automatic fire extinguishing device for battery cases with high temperature warning and automatic fire extinguishing function shall be arranged in the cabin."

This article again points out that the technical conditions required for the special automatic fire extinguishing device for the battery box are: the first can be early warning, and the second can automatically extinguish the fire. The early warning is the premise and basis of the follow-up automatic fire extinguishing action. If the early warning cannot be found at the very early stage, when the thermal runaway is extended and the battery box is on fire, the effect of the fire extinguishing will be greatly reduced; if the warning is false or false, it will lead to If the fire extinguisher is accidentally sprayed or not activated, the fire extinguisher may cause damage to the inside of the battery box, affecting the operation and safety of the whole vehicle; if the fire extinguisher is not started, it will not be able to effectively intervene at the critical moment of thermal runaway, and extinguish the fire in the initial stage, affecting the whole vehicle safety.

The emergence of "lithium ion battery thermal runaway model" technology has the advantages of extremely early, accurate and reliable, no false positives and false reports, and cost optimization. It is expected to become the best technical solution to ensure the safe operation of new energy vehicles.

"The lithium-ion battery thermal runaway model" is the core technology pioneered by New Energy. Its emergence has made it possible to monitor the thermal runaway of the battery box and the large-scale application of automatic fire extinguishing technology. The emergence of "lithium ion battery thermal runaway model" technology has the advantages of extremely early, accurate and reliable, no false positives and false reports, and cost optimization. It is expected to become the best technical solution to ensure the safe operation of new energy vehicles.

“The thermal runaway model of lithium-ion battery” is horizontal, vertical and vertical three-dimensional, and the data in the vertical direction is multi-sensor. It is to fit multiple sensor data in the same environment to simulate data of different materials and different environments. Characterizing the curve, reliable and accurate judgment of the fire stage; horizontally is a continuous time algorithm for the historical data of the sensor to eliminate noise interference, effectively solving the problem of false negatives, false alarms and early warning lag of the traditional threshold method monitoring method, achieving early reliability Early warning; vertical method using puncture, blunt needle backlog and other methods to simulate the thermal runaway process of different types of power batteries.

Through three-dimensional fusion, mathematical methods, based on a large number of experiments and real-life data, summarize the intrinsic relationship between various variables caused by thermal runaway, using neurological principles to form very early, highly reliable, self-operating "lithium ions" Battery thermal runaway model to achieve early warning and intelligent control of battery fire hazards.

At present, in the operation of new energy vehicles, a large number of early warning examples in actual vehicle operation prove the effectiveness and advancement of this model. Effectively avoid huge economic losses and avoid social safety accidents.

Case number one:

On March 12, 2017, a bus company's 3-way pure electric bus No. 3 battery box reported a level 2 warning (safety hazard level), and the driver reported the company in time and stopped the vehicle. According to the collected data analysis, the gas content and rate of change of other tank batteries were normal, and the gas content and rate of change of the No. 3 battery box were significantly higher. It is determined that the battery dangerous gas exceeds the standard, which may be caused by battery leakage. After the joint efforts of the bus company, the car company and the battery company, the unpacking inspection confirmed that the battery leaked. No more alarms after replacing the battery.

On March 16, 2017, a 4th battery box of a pure electric bus of a delivery company reported a second-level warning. According to the driver's description, the first level 2 warning was in December 2016, and the alarm disappeared after unpacking; the second warning was in February 2017, and the alarm disappeared after unpacking; this time is the third warning. The delivery company attaches great importance to the coordination of alarm system manufacturers, battery companies, and vehicle enterprises. According to the collected data analysis, the value and trend of the No. 4 box are completely deviated from other boxes. Combined with the previous alarm and disappearance, the initial determination is electrolysis liquid leakage. Unpacking inspection confirmed that the safety valve of a single battery was damaged due to unknown reasons and the electrolyte leaked. Seal the safety valve with tape and open the tape for 2 minutes to instantly smell the electrolyte. After opening the battery box, the device is again connected to read the data, and the alarm value is not reached. Reproduce the process of the first two alarm cancellations. After replacing the battery, it will not alarm.

On March 19, 2017, a pure electric bus of a public transportation company reported a No. 7 box 2 level warning, and the driver reported the company to the company in time and stopped running. The data analysis determines that the battery dangerous gas exceeds the standard, which may be caused by battery leakage. After the car companies and battery companies worked together, the unpacking inspection confirmed that the battery leaked. After replacing the battery, it will not alarm.

On March 20th, 2017, the ** delivery group county bus a pure electric bus reported the No. 3 box 2 level warning, the driver reported in time and stopped running. The data analysis determines that the battery dangerous gas exceeds the standard, which may be caused by battery leakage. After unpacking inspection, it was confirmed that there were unexplained leaks of the two batteries.

In the above-mentioned national standard technical documents, electrolyte leakage detection is a very important function. We don't know which of the 500 battery cells of a pure electric bus will deteriorate and become cancerous, but we can monitor it all. Once it is detected, it will be removed immediately, and these invisible safety hazards can be effectively controlled. Combined with fire-fighting devices and fire-resistant floors, the accidents will be controlled and intercepted in stages. The formation of a full life cycle hazard source monitoring system will greatly improve the safe operation level of new energy buses.

Forming a full life cycle monitoring system will also help improve the operational efficiency of new energy vehicles. Among all the battery cells, there are no destructive molecules that deteriorate the cancer, all of which are healthy individuals, which will ensure the battery life and service life to the greatest extent, thereby improving the operational efficiency of the transportation enterprises.

In practice, how to accurately detect electrolyte leakage in the early stage is a considerable challenge. The difficulty lies in both “early” and “accurate”, but also in a series of application environments such as “car” and “battery box”. Because the highly sensitive sensor will be affected by the volatile gas of the sealing material in the battery box, causing false alarms; the low-sensitivity sensor loses the function of early warning. It is well known that the consequences of the lag alarm are extremely serious due to the severity of the battery fire.

Another huge challenge is “high reliability” and “long life”. Since the device is sealed inside the battery box, the long-term warranty of 8 years and 120,000 kilometers is a basic requirement. The problem is how to make the system in a harsh environment for 8 years. Maintain high reliability. This involves a series of technical challenges.

From the practice point of view, the creation of the "lithium ion battery thermal runaway model" on the battery life cycle monitoring, especially the leak detection, has been proved to be effective.

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