The safety and reliability of electric cars has unfortunately been questioned thanks to nerve-wracking terms like ‘thermal runaway’ and headlines on burnt EVs that seemingly ignited for unknown reasons.

However, these fears should be put to rest. An electric car motor is actually less likely to set on fire than an internal combustion engine, with no liquid petrol or diesel present and fewer flammable lubricants like oil in and around the vehicle.

Of course, the top new EV models have to meet stringent safety regulations. Manufacturers are continually working to improve safety levels and cut risks even further through intelligent vehicle design and methods to isolate the high-voltage components.

 

Charging in the rain

Charging in the rain is one concern that can easily be dismissed. Electrical Safety First explain that the charging components of EVs are rain-proof, including outdoor public charging stations.

You should never use an indoor extension lead outdoors to extend the range of your charging cable. However, you shouldn’t use a standard domestic extension cable under any circumstances, so using a cable to charge the vehicle in the rain shouldn’t be a concern.

 

The lithium-ion battery

The lithium-ion battery (or batteries) used in electric vehicles are combustible, and short circuits are one way for damage to occur. Keeping the battery cool helps to tackle the risk of combustion, which is why more recent EVs often have refrigerant cooling systems like air conditioning for the battery and motor.

Older EVs might not have an active cooling system, but will normally have air inlets in the front grille. They may also have an aerodynamic underside to help guide the air flow pass over the hottest components.

Battery cell positions can have an effect on the risk level too. It's common for the cells to be arranged in an array rather than a solid block, distributing the heat further and reducing the risk of any individual cell receiving damage from a malfunctioning neighbour.

 

Safe temperature range of EVs

All of the above is about keeping the lithium-ion battery within its safe temperature range. This is typically between 15-45 Celsius. In comparison, the vehicle as a whole can be designed for anywhere from -30 to +50 Celsius or more.

Cooling, insulation, and other design tricks are all key to ensuring the battery stays at the right temperature. This helps to avoid safety risks when it gets hot, but also to prevent it from getting too cold and losing efficiency, which can affect the maximum driving range of the vehicle.

 

What is thermal runaway?

Thermal runaway is a process that can start when a high-capacity lithium-ion battery gets too hot. The battery ignites in a reaction that fuels the fire from inside the battery, resulting in a blaze that is extremely hot and almost impossible to extinguish from outside.

Clever vehicle design can help reduce this risk. There are fire protection systems for EVs that quickly dispense a cooling foam when a fire is detected, bringing the battery's temperature down and starving the fire of oxygen before thermal runaway can set in.

 

Centre of gravity

The location of heavy batteries under the floor of electric vehicles has an unexpected benefit during a crash. Because so much of the car's weight is so low down, the vehicle has a very low centre of gravity, making it more stable than a typical internal combustion engine vehicle. In a crash, EVs are less likely to flip or roll, and much more likely to stay on their wheels.

A report from the Road Safety Observatory noted concerns that, in a crash between a hybrid EV and an ICE vehicle, the ICE car might be expected to suffer greater deceleration forces, a consequence of the EV's greater weight. The report stated:

"There is some evidence to suggest that the probability of injury in a hybrid is lower than that in a non-hybrid, possibly due to the greater weight of hybrid vehicles.”

 

What additional safety features do electric cars have?

While electric cars have few features added solely for the purpose of safety, they have been designed to ensure they offer similar crashworthiness to ICE vehicles, including at the front end of the vehicle in the absence of a traditional engine.

Automatic braking and battery cut-off features exist on some models, and regenerative braking systems can also have safety benefits. Because the vehicle is designed to recover energy under braking, an EV may slow down slightly faster than a conventional vehicle would when you stop accelerating, reducing the risk to the driver if they are taken ill at the wheel.

 

What new safety features will electric cars have?

Looking to the future, electric car design will continue to develop and improve, although they are already very safe. 

As an example, a Tesla Model S was involved in an accident in 2013, which led to its battery combusting. Tesla responded by adding a titanium barrier to the vehicle design, creating a physical shield to prevent similar incidents in the future.

These kinds of 'bulkheads' are quite common and help to compartmentalise the battery, motor and high-voltage components. Awareness is improving during servicing too, with HSE guidance telling engineers to be wary of remaining energy stored in the batteries, as well as unexpected movements caused by electromagnetic forces acting on ferrous metal parts.

All of this means drivers can be confident about EVs. While there are safety risks, manufacturers continue to mitigate these as much as possible, and they are comparable with those of a conventional ICE vehicle. If anything, the research and real-world evidence so far shows that the top electric car models are safer than their ICE equivalents.