Are electric cars at particular risk of catching fire?

The risk of electric cars catching fire was both a popular and emotional topic of discussion in the media long before the fire on the Freemantle Highway cargo ship at the end of July 2023, for which electric cars were prematurely suspected of being the cause.  In this post, we try to get to the bottom of the issue as objectively as possible by examining the actual fire risk of electric cars and possible causes of fire, as well as the ins and outs of battery fires.

Electric cars also catch fire, but less often

Even if media reports sometimes suggest otherwise, insurers around the world have no evidence of an increased fire risk for electric cars.[1] Statistical analyses show that the fire ratio for electric cars is around 1:10,000.[2] Petrol and diesel vehicles, on the other hand, are seven times more likely to catch fire. However, this comparison should be viewed with caution, as it usually compares newer electric vehicles with petrol and diesel cars of any age. It will only be possible to make really well-founded statements in a few years’ time. Nevertheless, it can be said that electric cars cannot catch fire any more frequently than petrol and diesel vehicles.  In addition, field studies involving petrol, diesel and electric vehicle fires have shown that there is no significant difference in the fire energy released from vehicle to vehicle.[3]

However, the greater concern regarding electric cars is due to the fact that a completely different process takes place when an electric car battery catches fire, which also requires a different extinguishing method.

Electric vehicle fires are different, but no more severe

The undesirable scenario when a lithium-ion battery catches fire is a so-called thermal runaway, when one battery cell catches fire and then triggers a chain reaction in the other battery cells as it heats up.

When a battery cell ignites, the oxygen that accelerates the combustion process does not come from outside, but from the battery cell itself. So while a fire in a petrol or diesel vehicle can be halted by removing oxygen using conventional CO2 fire extinguishers, a battery fire can only be put out by intensely cooling the cells from the outside. This requires a lot of water over a longer period of time. Fire services have developed new methods for this, such as fire and waterproof bags that can be pulled over a burning vehicle and flooded with water.

What causes a battery fire?

The primary cause of a short circuit and therefore a potential fire in a battery cell in an electric car is severe external damage – if battery cells suffer mechanical damage due to an accident or external component fire, for example. In addition, lithium-ion batteries are generally subject to internal fire factors, such as construction defects or excessive charging currents, which have also caused problems with mobile phone batteries in the past. However, in the case of electric car batteries, spontaneous ignition without any external influence is unlikely to pose a real risk, as they are in a different category in terms of safety. The products used undergo rigorous testing procedures, and various safety mechanisms are installed to protect vehicles and occupants. Battery manufacturers use special materials that act as a kind of firewall in the event of fire in order to make the batteries more resistant to thermal runaway. A major difference between lithium-ion batteries in electric cars and mobile-phone batteries, for example, is the vehicle’s battery management system that constantly monitors and regulates the battery.

Can charging cause a fire?

In theory, overcharging or excessive charging currents could actually cause a short circuit in a battery cell while charging a lithium-ion battery. In the case of electric car batteries, however, this is highly unlikely, as the charging process is always controlled by the vehicle’s battery management system (BMS), which requests the required power from the charging station. So if there’s something wrong with the BMS, there will be no power. We are not aware of a single case in practice involving today’s electric cars when a battery fire has occurred due to the charging process. In addition, charging stations are fitted with effective fire protection mechanisms. Our certified systems are equipped with sensors that identify overheating or a faulty battery management system and can immediately interrupt the power supply regardless of the software.

Summary

Realistically, we can conclude that electric cars, like most appliances and machines, can also catch fire of course. But they do not catch fire any more frequently and are no more dangerous than petrol and diesel vehicles. The uncertainty is due to the fact that a battery fire develops differently to one that involves the components of a petrol or diesel car. Because the oxygen required for combustion does not come from outside but from the battery cell itself, a battery fire cannot be extinguished by oxygen deprivation, but only by external cooling. Fire services are prepared for this and have developed appropriate extinguishing methods. In addition to the fire protection materials used, the battery management system is also a major safety feature in electric cars. Among other things, it regulates the temperature, detects faults and also regulates the charging power. In addition to safety-approved charging stations, the functionality of the battery management system is another reason why the charging process is rarely a cause of fire. Ultimately, technology must be treated with due care and respect, even when it comes to electric cars. But panic is neither justified nor helpful.

Risk posed by charging stations in public underground car parks

As described above, rapid charging stations in underground car parks generally do not pose a fire hazard. Before installing our systems, however, a risk analysis is carried out and fire protection permits are obtained from the relevant authorities.

If a fire were to occur in a public underground car park, these have double protection in the form of fire alarm systems and sprinklers. Large underground car parks are also divided into fire zones that can be separated by fireproof shutters. When the fire protection system is triggered, the fire service is automatically alerted – it has the equipment to extinguish electric and petrol cars or other sources of fire in a controlled manner.