Electric cars and fire: real situation, causes and solutions

Electric cars and fire: real situation, causes and solutions

Electric cars and fire

For several years now, hybrid and purely electric cars have been available on the market, solutions that are rapidly gaining important market shares thanks also to the possibility of buying them with purchase incentives that lighten the price. While a few years ago it was very difficult to find and recognize, on the road, a car with a different fuel supply than the classic endothermic one, now hybrids and electrics far exceed the two million cars registered in our beautiful country; this is a small number compared to the current fleet, but still significant if we consider that only recently has there been a progressive incentive to purchase.

The diffusion of electric (and hybrid) cars has led with it a breath of fresh air, positive and negative, on several levels: from infrastructure to services, from equipment to use up to, of course (and fortunately), safety so as to limit possible risks in the event of an accident and/or malfunction .

Do electric cars catch fire more often?

We often report news of electric (or hybrid) cars affected by spontaneous or accidental combustion on our pages, causing continuous reactions (positive and negative) from our readers. The question we get asked most frequently is always the same: do electric cars catch fire more often than petrol ones?

We tried to answer this question by analyzing the numerous reports available and accessible to the public and the quickest conclusion is that endothermic cars are the most subject to situations of this type.

The most recent and complete study is that of AutoInsuranceEZ, a US portal that carries out a brokerage and comparison service between various insurance companies; in 2020, in the USA, many more petrol-powered cars caught fire than battery-powered ones. Numbers in hand, out of over 215,000 cars on fire, 200,000 are liquid fuel, 15,000 hybrids and just 50 or so battery-powered ones.

Clearly electrics are less widespread and it's not difficult to think that the result could be offset in this sense; looking at the percentage data, it turns out that every 100 thousand units sold, the cases of fire are 1,500 for petrol cars, 3,400 for hybrids and 25 for electric ones. Of course, there are some rare cases that could have, if not corrected in time, raised these numbers such as, for example, the problems related to the Chevrolet Bolt and its mega recall campaign of over 140,000 units.

Credits: Dominik Sostmann via Unsplash

The causes of a possible fire

The films of action broadcast on TV in the 90s and 2000s taught us, even emphasizing some aspects, that combustion cars can catch fire very easily especially when the liquid contained in the tank is ignited with some heat source. If you have ever seen an episode of Cobra 11 you have surely understood what we are talking about but you will also be aware that in truth it is not so simple and fast that a car can catch fire or even explode. But what are the causes related to electric cars?

In the common imagination, an electric car uses a "large smartphone battery" installed directly in the platform from which it recovers (and stores) energy to operate. Over the years there have been numerous recalls related to faulty and fire risk smartphones, is it possible that this also happens in cars?

What is a lithium ion battery made of

Lithium batteries are found in a large number of devices, they are safe but their use can involve a number of risks. Conceptually we can imagine lithium rechargeable batteries as a sandwich: the two slices of bread represent the plates (anode and cathode), while the ham is the electrolyte capable of conducting electricity.

At the start, the ions of lithium are positioned on the anode and only when the battery starts working the positive ions move, crossing the electrolyte, reaching the other surface. During the recharging phases, on the other hand, the "path" covered is in the opposite direction, bringing everything back to the starting situation.

The possible explosion of a battery is fundamentally linked to the overheating of the anode and cathode and the achievement of the of the “ thermal runaway ”. Each lamina, generally made of graphite, is covered with a special filter which prevents the electrolyte from corroding the anode and bringing it to temperatures capable of causing it to produce excessive heat (thermal imbalance). In these extreme and dangerous situations, the temperature can increase by up to 5 degrees Celsius per minute, causing the batteries to explode in the most extreme cases.

How is thermal runaway obtained? Simple, from a trivial short circuit of the electrical components, overheating from external sources, mechanical problems (such as a strong impact) or overloads.

Electric car on fire: how do the Fire Brigade work?

Managing "limit" events of this type requires special precautions, ad hoc equipment and prompt intervention, so as to avoid the risk that the electric car could burn for a long time and possibly even explode. To make a burning electric car safe, the Fire Brigade must not only wear all the appropriate protections, but also be able to safely disconnect the battery and observe it, with a thermal camera, to avoid a possible internal short circuit.

In this regard, as reported in this official document, some manufacturers (such as Renault) have installed special thermofuse covers also known as "Fireman access" on the battery pack to facilitate rescue maneuvers and operations extinguishing a possible fire.

If the problem should occur during the recharging phases, however, it is necessary to cut off the power supply, place the vehicle in a ventilated area.

Fireman access on Renault Zoe

The extinguishers that work better

A study on Effective Fire Extinguishing Systems for Lithium-ion Battery carried out in 2018 by the Sapienza University of Rome, ENEA and Nucle o Investigativo Antincendi, analyzed the real effectiveness of the most widespread extinguishers:

a stream of water; water mist (water mist); foam; CO₂; dry powder. Without going too far into technicalities that are difficult to understand, according to what emerged by simulating the cooling of a thermally runaway lithium-ion battery, water and foam are the most effective methods for cooling a battery. The water mist, introduced only in recent years to save on the liters of water consumed and to limit the damage created by the powerful jet of water, does not allow for proper cooling.

And what about CO₂? Carbon dioxide succeeds, as one might think, in suffocating the flame in a relatively short time, however, it does not allow the battery to be cooled promptly so as to interrupt the reactions that take place inside it.

Liters of water are never enough

Having established how to put out a fire in an electric car, one may wonder how many liters are needed; several news reports have appeared on the net in the last period regarding several Teslas that went completely up in flames. The two most striking cases come from the United States where 115,000 and 45,000 liters were needed respectively to put out the flames: these are extremely high values ​​especially if we consider that, on average, a tanker contains just over 10,000 liters and that for one between 2,000 and 4,000 liters of water are needed in the endothermic car.

Naturally, it took several hours to dispense all these liters of water. Furthermore, as if that weren't enough, the batteries can catch fire even after hours when perhaps the carcass is in a warehouse together with other cars or near a building, thus representing an unpredictable danger.

At the moment there are no reports of trucks or heavy electric vehicles in general that may have required an even greater number of water; however, we fear that in that case the effort on the part of the rescuers could be even greater.

The builders' strategies

While most of the builders have worked to offer "shortcuts" to the competent bodies to cool the most dangerous components, others, such as Audi, have managed to patent fire-fighting systems directly integrated into the lithium batteries. There are two solutions thought of at the moment and they operate in a distinct manner. The first is a system capable of recognizing and isolating malfunctioning cells, while the second provides for the integration of an extinguishing system capable of "sucking" the oxygen inside a module to directly "suffocate" the start of fire .

The structure of a battery pack

Can I park the electric car anywhere?

One may ask oneself, also with a view to possible help, whether it is possible to park the electric car in every parking lot or if, similarly to natural gas cars, there may be possible limitations. At present, in Italy and in Europe there are no limitations in this sense, but only generic guidelines (advice and indications) for public garages and recharging systems that must be installed to favor rescue operations.

Different speech for the transport by ship which, following the fire of the Felicity Ace, has opened a huge debate on safety on board. In this regard, it seems that new-concept cargo ships capable of containing and taming potential fires caused by electric cars will be built; the first will be called Aurora and should enter service in 2024.

Is there a real danger in electric cars?

Absolutely not and the risks that can be run are the same as those of endothermic, with the only difference linked to the extinguishing system which requires a decidedly higher effort in battery-operated ones.

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