Why is it so difficult to put out a fire when a new energy vehicle catches fire?

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Why is it so difficult to put out a fire when a new energy vehicle catches fire? [Copy link]

It turns out that Mr. Zhang, the chief designer of electric vehicles, said that the design of lithium battery packs for electric vehicles is very important. The safety and reliability of the heat dissipation design of lithium battery packs must be guaranteed, and the battery management system (BMS) must monitor battery overheating in place. Generally speaking, safety problems with lithium battery packs manifest as combustion or even explosion. The root cause of these problems is thermal runaway inside the battery. In addition, some external factors, such as overcharging, fire sources, extrusion, puncture, short circuits, etc., can also cause battery fires and explosions. Therefore, the design of lithium battery packs is very important. If it is not done well, it will cost lives. Let's review those electric vehicle fire incidents. In 2014, an electric car in Texas caught fire on the road, with flames as high as 2 meters, and was finally burned to an empty shell.

In 2015, at about 9:30 pm on November 20, a rear-end collision occurred under the Keyuan pedestrian overpass on the North Ring Road in Nanshan District, Shenzhen, from east to west. A van rear-ended a BYD e6 electric taxi (license plate number: Yue B·H8L49) that was driving normally, and the front of the van was stuck in the rear of the taxi in front. The accident caused a fire in the front of the van behind, and liquid was left. Both vehicles were burned, and there were no casualties.

At 12:22 on May 1, 2017, a series of electric bus fires broke out in the parking lot of Beijing Xiedao Resort. Due to the May Day holiday, more than 100 new energy electric buses were parked. According to on-site visual observation, about 80 buses caught fire.

Through the review of the above electric vehicle fire incidents, we can find that once an electric vehicle catches fire, the fire will be extremely fierce. Even if the fire is extinguished, the final result is basically that the entire vehicle is completely burned.

Why is this so?

First, let's take a look at the scene of a single lithium battery catching fire in the figure below. (This single battery is not lithium iron phosphate. After being punctured by a needle, the genuine lithium iron phosphate battery will generally emit smoke and will not catch such a big fire.)

As can be seen from the above figure, once a single battery in the electric vehicle battery pack catches fire, the fire will be short and large. A single problem may quickly cause the lithium batteries in the entire battery pack to catch fire. Just like what some friends described, an electric car caught fire, and after putting out the fire here, another fire started somewhere else, but in the end, the fire could not be put out.

Let's take a look at the distribution of these lithium batteries in the body of an electric car:

The lithium battery pack of an electric car is generally installed at the bottom of the car body. Once the lithium battery pack catches fire, it may directly threaten the safety of the passengers in the car. Therefore, once the electric car has signs of fire, the passengers in the car should leave the electric car immediately. If the power can be cut off, it must be cut off immediately, and the car key must be placed in a signal shielding bag and the bag must be placed 10 meters away from the vehicle.

Here, it should be noted that when lithium batteries burn, they will release a large amount of toxic and harmful gases. Pedestrians should try to stay away from the burning electric vehicle and not to watch the burning vehicle to prevent poisoning by toxic gases. Firefighters should wear gas masks. Lithium battery fires should be extinguished with a large amount of water. After the fire is extinguished, monitoring should be continued to prevent the fire from catching again.

Although the energy storage density of ternary materials is very large, its safety is not as good as that of lithium iron phosphate. Therefore, commercial vehicles generally require lithium iron phosphate batteries to ensure the safety of passengers. In short, when an electric vehicle is hit, or the battery management system (BMS) alarm shows that the temperature of a single cell is too high, attention should be paid to prevent the lithium battery from catching fire. Once a fire is discovered, do not try to extinguish the fire and move away from the burning vehicle as quickly as possible.

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cbyellt

The electric car caught fire, and it was just a run.

alan000345

cbyellt posted on 2018-7-14 13:36 If an electric car catches fire, just run away

You are right. At present, if a lithium battery catches fire, the owner can only stay away from it as soon as possible. At the same time, try to notify passers-by to stay away.

Harburr

This may be due to the material of the battery... I don't understand either, but my company is engaged in automation equipment. A while ago, I heard from a colleague that they had set up a Feneng automated production line, which is responsible for testing the 18650 lithium battery pack line. I think if it is tested before being used in the car, it should not be easy to break...

wex719

Harburr posted on 2018-10-9 15:34 This may be due to the material of the battery... I don’t understand it either. It’s just that the company is engaged in the production of automation equipment. Some time ago, I heard from a colleague that they specially made a Finneng...

It has nothing to do with whether it has been tested or not. It is determined by the characteristics of the battery!

chijiaoshenshi

Thank you for sharing your knowledge. It turns out that lithium battery fire is so serious.

MagicBeans

Thanks for sharing your knowledge