Editor's note
After the power battery works, it is inevitable to be hot. Under normal conditions, it is controllable, but it will lose control under abnormal conditions. If it is out of control, a fire will inevitably occur. Technically, it must be clarified that analysis of the cause of loss of control is a must.
The thermal runaway mechanism of power battery packs, many universities and research institutes are specializing in project research, and the bus companies are urgently needed to have a theoretical basis, which has been approved by authoritative organizations and has technical content. At present, bus companies are confused about this. The main reason is that one assembly of power battery packs is purchased by bus manufacturers. At present, power battery pack products are far away from the requirements of bus companies.
I. Analysis of the cause of thermal runaway of power battery
After the power battery works, it is inevitable to be hot. Under normal conditions, it is controllable, but it will lose control under abnormal conditions. If it is out of control, a fire will inevitably occur. Technically, it must be clarified that analysis of the cause of loss of control is a must. To sum up, there are two basic reasons: internal and external:
(1) External factors: over-charging triggers thermal runaway, external force causes thermal runaway, and overheat triggers thermal runaway;
(2) Internal cause: The internal short circuit of the battery triggers thermal runaway.
The power battery is an energy system, and work must be hot. To ensure absolute safety, it must be controlled from the engineering and reliable technology to ensure that its fever is controllable.
There are two basic ways to guarantee: First, there is an early warning, and personnel intervention can be carried out in advance. However, if the warning function fails, there must be an automatic fire extinguishing function. If the above two are done, the safety of the power battery pack will naturally be guaranteed.
Second, the power battery pack thermal runaway warning and fire fighting is a whole
It is mainly composed of a single-type power battery fire alarm control device and a new gas automatic fire extinguishing device for power battery. Intervention control and fire emergency automatic fire extinguishing, with multi-sensor composite detection, full-cycle fire detection, thermal runaway monitoring analysis and early warning, emergency control fire extinguishing, etc., to detect the early warning intelligent control of the power battery pack fire hazard To maximize the protection of electric vehicles and passengers.
The actual vehicle products must require the compact size, flexible installation, convenient operation and maintenance, green environmental protection, strong adaptability, etc., in terms of function (performance), fire detection and early warning, self-starting, manual start, etc., to meet the fire-fighting efficiency. And effect requirements.
Third, the basic function of the thermal runaway warning of the power battery pack
For the intelligent management of the thermal runaway of the power battery, it is necessary to realize the initial detection, intelligent analysis and early warning of the battery fire. The main functional requirements are as follows:
Accurate identification early in the fire
Full cycle fire detection record
Intelligent judgment, linkage fire
Data black box function, data tracking
There is no residue of fire extinguishing agent, no damage to electrical equipment
Long life, light maintenance
Open interface, information sharing.
Fourth, the power battery thermal runaway warning and fire extinguishing system principle
(1) Power battery thermal runaway warning system
The system monitors the real-time parameters of the CO-gas, smoke, temperature and flame detection points in the battery box and their change values, and uses the data monitoring model to dynamically analyze and process the parameter changes to intelligently determine whether there is a risk of thermal runaway fire. The power battery fire alarm control system is as follows:
(1) The working principle is as follows:
When the power battery fails and begins to relieve pressure, heat, etc., the detector can detect abnormal changes, and send the warning signal to the driver through the CAN bus or the wire harness in the potential stage of the fire, the smoking stage, the high temperature stage and the open flame stage. Achieving grading warning and controlling the start of the fire extinguishing device, the system can intelligently judge and automatically start the fire extinguishing device to prevent the fire from deteriorating, and can also manually start the fire extinguishing device in an emergency state. The fire extinguishing device controls the fire in a few seconds through a high-efficiency fire extinguishing agent to maximize the safety of the battery pack.
(2) Introduction to product examples
The device has the advantages of small size, easy installation and layout, excellent quality and environmental adaptability, multiple stages of multiple detection, advanced data analysis model, precise and rapid control response, and dynamic programming and intelligentization.
The out-of-control early warning device is an integrated design integrating active detection, data analysis, control, control and management. It contains high-sensitivity temperature sensor, gas sensor, smoke sensor and flame sensor. It is installed in the battery compartment of the power battery. The automatic fire extinguishing device and the BMS management system are docked to detect the gas, heat, smoke and open flame generated in the initial stage of the fire due to internal short circuit, over charge and discharge, external short circuit, etc. The system intelligently analyzes the battery thermal runaway stage and performs automatic intervention control. .
(2) Special gas automatic fire extinguishing device for power battery pack
The gas automatic fire extinguishing device for power battery packs is stored without pressure every day, and the fire extinguishing agent has excellent performances such as moisture resistance, temperature resistance and corrosion resistance. In the event of a fire, the device initiates the action of the fire extinguishing agent through an electric start or a temperature-sensing start mode, rapidly generating a large amount of sub-nanometer solid phase particles and an inert gas mixture, and is highly submerged in a high-concentration flue gas type for each fire occurrence. The corner, through physical cooling, chemical suppression, dilute oxygen multiple effects, quickly and effectively extinguish the fire, no harm to the environment and personnel.
The gas automatic fire extinguishing device for power battery pack has significant advantages in terms of volume, weight, fire extinguishing efficiency, environmental performance and convenience. Products based on national and industry standards, according to the power battery system to protect the space environment and its own characteristics, after a large number of experimental development and molding, with small size, fast and efficient, safe and easy to use, convenient operation and maintenance, green and environmental characteristics.
(1) Description of the fire extinguishing mechanism:
(2) Description of the starting mode of the fire extinguishing device:
(1) Electric start
When a fire occurs, the detector transmits a signal to the fire controller, and the controller activates the fire extinguisher to extinguish the fire by an electric signal; or manually controls the electric start button to start the device to extinguish the fire.
(2) Thermal line temperature line start
When the temperature reaches 170 ° C, or when there is an open flame, the thermal line senses temperature and spontaneously ignites, and quickly transmits a start signal to the fire extinguishing device to quickly extinguish the open flame.
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