Lei Feng: press author: Zhu Yulong, Automotive Engineer.
At the front end, the Ministry of Public Security issued the “Circular on Enhancing the Prevention of Electric Vehicle Fires in Residential Areasâ€, where the electric vehicles (electric bicycles, electric motorcycles, and electric tricycles), we will talk about the fire safety of electric vehicles this time. .
Compared with the safety of traditional cars, battery cars are mainly high-voltage and lithium-battery safety issues. The explosion and burning of lithium batteries is a manifestation of thermal runaway. The main reason is that the thermal energy generated when the ternary electrode material is thermally decomposed is higher than that of lithium iron phosphate and generates oxygen.
| Electric Vehicle Fire ConfigurationUS NFPA "Emergency Emergency Guide for Electric Vehicles" Reference Documents 1. The National Highway Traffic Safety Administration's "Interim Guidelines for Electric and Hybrid Vehicles Equipped with High-Voltage Batteries" recommends the use of continuous, large quantities of fire-fighting water as an extinguishing agent.
The point of consideration here is mainly for the car:
The high-voltage battery has a protective shell and it is difficult for the fire extinguishing agent to reach the battery unit directly.
A large amount of water can cool the battery enough to prevent the flame from spreading to neighboring cells.
Remarks: According to the method of contacting the battery, it is considered that Fire Fighter Safety and Emergency Response for Electric Drive and Hybrid Electric Drive Vehicles. Quincy believes that the use of dry powder, carbon dioxide and foam fire extinguishing agents is better.
Battery A (4.4Kwh) requires 275-1060 gallons of water
Battery B (16.5kwh) requires 1165-2639 gallons of water
Some basic conclusions
The flow rate of water is greater than expected to destroy traditional car fires (the water consumption is significantly larger than that of conventional diesel locomotives)
Continuous water flow on the battery reduces the temperature and shortens the extinguishing time, but the total amount of water increases
Remarks: If there is no water
Where there is no water source on site and there is no threat to (human life safety, buildings, vehicles), allowing the battery to self-extinguish may be an effective choice for extinguishing the fire.
It takes longer to monitor and observe any re-ignition. The free burning test lasts for about 90 minutes with visible flame.
The extinguishing agent extinguishes the battery may renew
When using water to extinguish high voltage batteries, use a lot of water
Using a small amount of water will release hazardous toxic gases
We need to consider the following scenario:
A. Normal use
Electric car charging.
In general, we can divide AC and DC charging. We must pay particular attention to the DC charging station near the expressway. It will be analyzed separately tomorrow. Imagine if there would be a mass accident at the charging station in the future. If an electric vehicle ignites a nearby vehicle and the charging station itself is burning, this will be a big deal.
Normally, DC chargers cannot use water until they are powered off.
Identify and locate the energy source in the charging station and turn it off
The electric car is connected to the charging station. Once it is safe, it should be unplugged. (At present, there are electronic locks on the DC charging points, so it is not easy to disconnect.)
If possible, first turn off the charging station.
Until the capacity of the charging station is cut off, it is like putting fire on other charged fires.
Electric vehicle driving: It mainly analyzes under various working conditions. This section mainly considers the safety design of the vehicle system.
B. Traffic accidents
Electric vehicle after collision
1. If the high pressure system of the detected vehicle is damaged
Vehicles should be stored in isolation
Stay away from buildings, other vehicles, or combustibles
2, can not be placed in the building
3. The doors and windows shall be fully opened and ventilated to avoid accumulation of flammable gas.
4. Isolation with obstacles, using steel and concrete structures, four-sided obstacles
5, try to consider the discharge
C. Maintenance scope
The electric car enters the maintenance area: The electric car entering the maintenance area is equal to the battery to be replaced, the damaged battery, and the maintenance area of ​​the 4S shop as a whole becomes a fire-sensitive area.
Replacement battery in an electric vehicle repair station
Here put together that, in fact, for car manufacturers, the maintenance of an electric car after the sale is very terrible. Do you think about how the battery is handled?
D. Transportation
During the transportation process of an electric vehicle: a vehicle is burned once during transportation. Overall, this aspect needs to consider certain risk aversion. These cars are all packed together. Even if it is a trailer, how can it be extinguished?
The problem of battery packs in the transportation process: air transportation, land transportation, etc. Actually, the former has a very good approach, and there are many opportunities to explore the process of land transportation.
The 10kg battery changer is a concept that may be an option on electric bikes and future vehicles, but the risk spreads all the way to office and home areas. It is more difficult for consumers to recognize this issue and the potential risk of doing so is really too great.
| Summary1) In the summer, the first batch of electric vehicles aging, the owner’s perception of electric vehicles will increase the exposure record of the problem. When our inventory reaches 60W+, the problem is sure to continue.
2) From the blueprint of the system, we need a little bit to see how to find the problem and how to solve the problem. Open up and throw a brick out
Reference materials
Best Practices for Emergency Response to Incidents Involving Electric Vehicles Battery Hazards: A Report on Full-Scale Testing Results
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