EV batteries or gasoline car. Which is more dangerous?

Do EVs really spontaneously ignite?

You could be mistaken for believing that electric cars are bursting into flames everywhere you go. The media coverage makes the viewer believe that EVs are dangerous. But are they?

It might surprise you to know that official data in the US from 3 different national agencies (including the US National Transportation Safety Board and Bureau of Transportation Statistics) for 2022 came to a completely different conclusion:

The number of car fires in 2022 were as follows for every 100,000 cars sold:

• 25 fires in electric cars
• 1,530 fires in petrol or diesel cars, and
• 3,474 fires in hybrid cars

There! I told you that you would be surprised. The main cause of fires in electric cars is most likely to be a bad accident and not (as the media would have you believe), and I repeat, NOT spontaneous combustion!

In that same year, here’s the TOTAL number of fires per vehicle type:

• 52 fires in electric cars
• 199,533 fires in petrol or diesel cars, and
• 16,051 fires in hybrid cars

Whichever way you cut it, the fire risk of electric cars seems to be minimal. Remember, fires do happen.

Safety Compliance is for All Cars

The media would have you believe that there is a problem with battery safety.

Car batteries are not a big cavernous bucket of chemicals that transport electrolytes that slosh around. The battery architecture is a complicated and complex arrangement of cells and modules within the platform. Its function is managed by the Battery Management System (or BMS) which oversees safe operation and which includes the management of heat (thermal energy).

It is interesting to think that there are millions of people who distrust high-tech batteries, even though they are happy to drive at high speeds in a petrol or diesel car. It doesn’t take much to realize you are sitting on top of many gallons (or liters) of highly flammable gas, all the while moving around at the same time that literally hundreds of thousands of explosions occur beneath your butt.

EV Safety

Be that as it may, for any car to be on the road, it has to comply with countless regulations that ensure it is safe to operate, safe for occupants, and safe for other road users. EVs have gone through that process too. And if those stats above are anything to go by, you could argue that EVs are indeed safer than ICE (gas/diesel) cars. Those same regulations have meant that modern cars (and no longer just the expensive ones) have incorporated many design features such as airbags, ABS, electronic stability control, lane assist, collision avoidance and much more.

Fire Risk in EVs

There have been some electric vehicles recalled over fire risk. These recalls were a mix of issues of concerning parked cars, EVs being charged, being driven or with a perceived greater risk in the event of an accident.

Reports include that of an exploding car in Montreal (in the garage of a private home), an exploding Tesla after a high-speed accident, a couple of BMW EV variants recalled due to the battery with a manufacturing defect (before accidents occurred). Hyundai Kona 2018 and 2020 models and the MG HSEV (2021/22) had battery manufacturing defects. But hey, the list of recalls of gas and diesel cars is huge and growing. The older a gas car gets, the higher the fire risk. The wear and tear on the thousands of tiny parts of an internal combustion engine, the wear on the wiring which become loose and frayed over the years are all areas of concern and must be checked frequently.

It’s probably important at this point to look at the fire risk of gas cars, so you can be really objective about it. EV fires get so much attention. You rarely see news of a gas engine catching fire. Probably because they are so commonplace. Almost 200,000 fires per year (minor to dangerous) is over 500 fires on average per day. You see more EV fires reported because at the moment, the EV industry is under greater scrutiny because it’s in a state of massive growth and the technology is advancing at lightning speed.

Fire Risk in Gas Cars

Here’s a little snapshot of the problems often encountered with gas cars:

• There are several flammable and dangerous fluids are under the hood. These include gasoline or diesel, engine coolant, power steering fluid, brake fluid, and engine oil.
• A bad gasket means flammable liquids drip onto a hot engine.
• The most common cause of all vehicle fires is leakage in the fuel system.
• Over 20% of car fires are due to electrical failures or malfunction of the electrical system.
• Leaks, frayed wires and faulty wiring, broken parts, leaky seals, are all items that need to be frequently checked and if found, fixed.
• An overheating engine causes the temperature of fluids such as oil and coolant to rise, expand, and spill out of their contained areas. They escape and drip or spurt into the engine bay. Many fires are caused by contact of these flammable liquids on the exhaust system or hot engine.

Tesla has claimed that gas cars are eleven times more likely than a Tesla to catch fire. They have suggested that the best way to compare safety data is to look at fires per billion miles driven. That’s an interesting viewpoint. There are five EV fires per billion miles, compared with 55 fires per billion miles traveled in gas cars. As the uptake of EVs increases, more data will be available to make a more reliable comparison.

Gas Versus EV Cars. Which is Safer in a Crash?

Accidents do happen, and outcomes with EV batteries have been poor. Notably, extinguishing a battery fire can be difficult. Batteries experience a phenomenon called thermal runaway. This creates the possibility of a battery fire restarting, even after it appears to have been put out. The most effective way to extinguish an EV fire is to manage the fire, then cover the car with a special car fire blanket for 24 – 48 hours. Doing so will minimize risk of a further electrical fire.

These days, EV batteries undergo many compliance tests; chemical, thermal, electrical and mechanical safety tests. One such test is a nail penetration test where a nail forcibly penetrates the battery. It simulates internal short-circuiting. If the battery does not catch fire or burst, then it is deemed safe. Batteries are constantly being developed and improved to have increased resistance to fire events, and have systems to cope with punctures of the battery (and other incidents) to maintain safety.

Temperature Control

Lithium-ion batteries have an ideal range of operation and optimal use, efficiency, longevity, and for safety the battery is designed to stay within that range. This is where the Battery Management System (BMS) comes into play with sophisticated heating and cooling algorithms (which are more complex than the type of battery you would find in your phone or even an electric scooter). Temperature is constantly monitored, and the battery is cooled with the use of air cooling (with air ducts) and liquid coolant around the battery cells and modules.

Thermal Runaway Explained

Thermal runaway (as it pertains to EV batteries) is a chain reaction that occurs when the heat generated within a battery is greater than the heat it is releasing to the surroundings. It is caused by mechanical or thermal failures brought about by puncture, short circuit, overheating and even an excessively high discharge rate. The temperature above which this reaction becomes a risk is 140F or 60C.

EV batteries are more and more high-tech. They are designed to avoid thermal runaway and limit damage in the event of malfunction. Runaway is very rare these days because of advancements in battery tech. A cooling shroud of liquid surrounds the battery to prevent overheating. But it’s not just this shroud that does the work. The battery is made up of cells. Groups of cells make up modules within the battery pack. These modules (also called clusters) are separated by firewalls. The concern is that thermal runaway could take over, because of the inherent energy stored in the battery, which could make a fire last longer than expected.

So, to sum up, battery design has virtually eliminated the risk of internal short circuits to cause problems such as fire and thermal runaway. However, the risk of external short circuits due to an accident may not be unavoidable.

Thermal runaway doesn’t occur with gasoline and diesel cars. The fire risk is different. It is far more common. Gasoline fires have a high risk because the gas ignites the instant fuel encounters a spark of flame. And this is how a gas car actually works. It relies on explosions being created constantly. It’s part of the wonder of an ICE car but also one of its biggest problems. EVs solve that issue because even though a Li-ion battery in an EV can (rarely) catch fire, there is a hugely and significantly lower risk of fire or explosion. An EV accident might damage the car itself, but most accidents do not involve the battery. It takes a rare and major accident to cause severe damage to pierce or affect the battery pack itself.

Physical Design of EV Batteries

There are ways to physically reduce risk. All the following factors are of benefit to the driver, passengers, other people, including emergency service workers.

• Thick metal battery casings are a barrier. (They add to the weight of an EV battery and why EVs can be comparatively heavy.)
• Battery is positioned away from the common (accident) impact zones.
• Batteries of different battery chemistry. One emerging technology is lithium-ferrous-phosphate or lithium-iron phosphate or LFP or blade battery.
• BMS of modern batteries automatically disconnects the battery at various points when airbags are deployed (when triggered by an accident). In this way the risk of the high voltage starting an external fire is greatly mitigated.

Lithium-Ferrous-Phosphate Batteries

LFP batteries have a reduced runaway risk and a wider optimal operating temperature range. BYD (Build Your Dreams) the Chinese EV manufacturer, uses its LFP Blade Battery. They claim their batteries have superior safety characteristics. Take a look at this video demonstrating the nail penetration test. They have successfully subjected the blade batteries to these varied physical tests without producing fire, smoke or exploding:

• Nail penetration
• Bending
• Crushing
• Extreme high temperature
• Over-charging

Tesla, Volvo, Ford, VW, MG and GWM have started (or have imminent plans) to use LFP in certain models.

An interesting titbit: In Australia, the car safety regulatory authority has not reported any battery fires from all the BEV models in that country since 2011.

Battery Location and Accessibility

The position of the battery deep within the car, and low down to give the whole car a low center of gravity, is both a positive and negative aspect. Positive when the battery is not involved in an accident, and a negative could be that access is more difficult if the battery ignites for any reason.

In an accident, first responders need to know how to deal with high-voltage situations. The fire-fighting industry has had to be educated on many factors, including how to isolate the low voltage (LV) and high voltage (HV) systems. The 12V accessory battery is likely located under the hood or under the floor of the boot. There may be a marked cut loop or pull fuse. Manufacturers have different ways to make this information available including smartphone apps for rescuers or even QR codes fitted to the vehicles. Fighting an EV fire does take specialized equipment. In Holland in 2019, firefighters attended a fire in a HYBRID (and remember these are far more flammable than a gas car) and the car was lowered into and submerged in a water bath for 24 hours.

For a handy guide of what is important for first responders to recognize, take a look at this Australian website. It has some very interesting graphic descriptions you may find useful. The corresponding US information has links that may interest you.

Battery accessibility is a current field of improvement in EVs!

Electrolyte

Much research and development continues to evolve battery chemistry. R&D tackles the issues of energy density of the battery, thermal runaway and the flammability of electrolytes and the physical structure of the battery itself.

The problem with electrolytes in lithium-ion batteries is that they potentially can catch fire. This is why batteries are not just a single module container with electrolyte sloshing around allowing movement of electrons between cathode and anode. Car batteries are made up of thousands of cells, and those cells make up modules or clusters. There are firewalls that separate the units to prevent a chain reaction and fire spread. At best, these contain the fire. At worst they delay the spread to other portions of the battery.

The chemistry itself is the focus of R&D. Breakthroughs are constantly being reported of laboratory success using ‘safer’ electrolytes (less flammable, and which produce less harmful chemicals). LFP batteries are one such advancement. Sodium-ion batteries are another battery type that is likely to evolve to the point of manufacture in the future. Solid-state batteries are being tested.

Fire Risk Compared

For the moment, and according to official stats from the US, the proportion of EV fires is minuscule compared to gasoline/diesel cars and even more tiny when compared to hybrid vehicles. The 2022 stats concluded that from every 100,00 sales of EVs, there were only 25 fires. The stats for gas and hybrid cars were shocking. See the table. The stats are even more alarming when you look at overall fires, but there are many more ICE vehicles than either EV or hybrid. Here are those stats again at a glance:

When gasoline and diesel engines ignite for any reason, the very nature of liquid fuels, means ICE fires can spread and engulf neighboring property and endanger lives of people standing by.

At the moment, it seems evident that while it is far less likely for an EV to become engulfed in flames, the fire is more difficult to extinguish. Safety in EVs, and the risk of battery damage and fire, is taken very seriously. Advances in technology in combustion engines (ICE) and EVs, are constantly being made that are steadily reducing the incidence of fires. The big take-home point is this: The hype and propaganda around fires in electric vehicles is grossly overstated.