Batteries lithium : un risque d’incendie très faible mais difficile à maîtriser

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Electric buses burning in Paris, scooters emitting smoke before burning, cargo ships sinking following a fire in the electric vehicles transported… These cases of fire remain very rare. But their fire control is still a headache for firefighters and manufacturers.

In April 2022, a electric bus caught fire in Paris. Last July, a cargo ship caught fire off the coast of the Netherlands. On board were 3,783 cars, of which nearly 500 were electric models. Three years earlier, the cargo ship Höegh Xiamen sank after a fire in the second hand battery of a car.

Videos were also posted on social media showing scooters or smartphones catching fire. These cases are very rare but increasing, because there are more and more electric vehicles. According to the report on the activities of the Montreal Fire Department (SIM), 24 fires caused by lithium-ion batteries took place in 2022, or 3.5 times more than in 2021.

Contrary to popular belief, the quality of Chinese batteries is not always the main cause of these fires. This is the very conception of batteries lithium-ion which poses a problem.

Most lithium-ion cells combine highly reactive materials in a very compact space that, to make matters worse, are near volatile and highly flammable electrolytes.

Drown a car

When the barriers separating these reactive materials are damaged, a chain of chemical reactions generates heat. This creates a domino effect where the temperature can reach a difficult to control value of 700 to 800°C. The material separating the anode and cathode will melt and cause a short circuit.

This is called thermal runaway. But how can we avoid reaching this fateful threshold? “Some vehicles are equipped with forced ventilation, however less effective than the cooling circuits that can be found on more high-end vehicles”notes Lilian Chavanon, who runs Chavanon Conseil, a company specializing in risk management.

Another often overlooked risk is that a battery can catch fire 72 hours after an impact. The sensibility [des batteries, NDLR] to mechanical shock (following an accident or a fall if it concerns the battery of a smartphone or an e-mobility device) or electrical shock is, in fact, very high. It can cause internal damage: cell deformation, liquid leaks, risks of overheating and again short circuits.

The situation is all the more worrying since firefighters today do not know how to quickly extinguish a burning electric car… Conventional extinguishing agents are generally ineffective, because these batteries produce their own oxygen, thus fueling the fire.

“The best thing we can do is to send water inside the battery in order to cool the modules and avoid the risk of propagation to other modules. The cell will thus be completely consumed without affecting the others. But you can never be sure that a battery has completely burned and that the fire will not start again. This is why one of the recommended options consists of drowning the car with complex logistical and environmental constraints. The Monaco firefighters have an isolation container in which they place the car once the extinguishing is complete in order to ensure monitored monitoring of the battery, coupled with an extinguishing device.specifies Lilian Chavanon.

Second-hand cars

According to Tesla, it generally takes between 11,000 and 30,000 liters of water to put out a fire in an electric car.

But the case of vehicle batteries is not the only one to pose problems. Businesses are also affected. And the risks are also significant. At the beginning of 2023, a fire in a building of the Bolloré Logistics company in Grand-Couronne mobilized around a hundred firefighters for several hours.

The fire started in a lithium battery storage facility and then spread to a nearby warehouse where tens of thousands of tires are stored. “This fire was the revealing element for many industrialists. Logisticians who store car batteries, scooter batteries or those connected to photovoltaic panels must set up detection systems”warns Lilian Chavanon.

But still too many companies are not aware of the risks. However, they accept that employees come to recharge their vehicles in their parking lot but also bikes and scooters on the premises, without integrating these fire risks into their Single Risk Assessment Document, the head of Chavanon Conseil told us.

These various cases suggest that these batteries present a threat to businesses but also individuals. In fact, they are very safe if properly used and maintained. It is important to read the instructions for use carefully to minimize the risk of fire.

“If we follow good charging and discharging practices, normally there is no reason for it to catch fire. On the other hand, I will not buy a used electric car, because I do not know how the previous owner managed his battery on a daily basis and how the battery will react after several years of use. This is the reason why Renault’s formula which rents batteries is interesting”note Lilian Chavanon.

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