Electric vehicles (EVs) are no longer a thing of the future – they are rapidly taking over our roads and changing the face of the transportation industry as we know it. For centuries our transportation industry has been fueled by fossil fuels and internal combustion engines. However, in 2022, we saw a massive pivot as the integration of electric vehicles was highly prevalent. In a year when new car sales dropped dramatically due to the economic climate, Tesla sales skyrocketed. Year over year, Tesla saw a growth rate increase of more than 77% [1]! Alternatively, internal combustion engine manufacturers like Ford, Toyota, and Honda, saw sales dip at a rate of -2%, -9%, and -33%, respectfully, in the same year.
As more new electric vehicle owners are introduced to the road, it is imperative that they are aware of the unique failure mechanisms that exist within an EV. Understanding these failure mechanisms will ensure safety while operating and storing the electric vehicle and will lead to a prolonged lifetime on the road.
EV Anatomy
EVs are equipped with the following unique electrical components to enable the vehicle to be solely powered by electrical energy:
- Electric Motor: Electric motors are used to power the wheels while driving. These motors are located above each axle.
- Battery Pack: A Lithium-Ion battery pack stores electrical energy to power the electric motor. The battery packs are generally located underneath the passenger compartment.
- Charging Port: Charging ports allow the battery to recharge after consuming its electrical energy. These port locations are unique to each manufacturer and/or model.
- Onboard Charger: Converts the AC power received from a charging station to DC power to charge the battery pack. Located between the charging port and the battery pack.
- Regenerative Braking System: Converts energy developed during braking to charge the battery pack while operating. Located on each axle.
- Thermal Management System: Regulate the battery pack temperature, ensuring it is kept within safe operating temperatures. Located throughout the vehicle.
EV Failure Mechanisms
Electric vehicle failures can be catastrophic because of their unique design. Electrical energy is designed to be active at all times, and the battery pack is protected from its exterior. However, like any device, they are not immune to failure. Understanding the potential failure mechanisms of EVs and their unique components is essential for maintaining the vehicle’s and its owners’ safety.
The most abundant failure mechanism within an electric vehicle lies within the lithium-ion battery pack. A process called “Thermal Runaway” can cause an EV to spiral out of control, resulting in an uncontrollable and continuous production of heat. This can quickly result in toxic gas release and a fire that can be very difficult to extinguish. The following are examples of how a battery pack can enter a thermal runaway state:
- Over-Charging: Causes reduced lifespan and battery performance. Additionally, over-charging a battery can create excess heat within the battery. This, paired with additional external heat sources, can lead to thermal runaway, and potentially lead to a fire.
- Charging Stations Failures: Charging station wiring is exposed to the elements, meaning they are susceptible to degradation over time and continuous use. Additionally, supercharging a vehicle with a higher amperage than recommended can significantly reduce the battery and, in some instances, cause battery failure.
- External Heat Sources: High temperatures can cause the battery pack to degrade quicker, reducing its performance and lifespan. Extreme high temperatures can cause the battery to expand, leading to a failure and potentially a fire.
- Physical Damage: Physical damage caused by a vehicle collision can be catastrophic for an electric vehicle. Significant collisions can lead to battery puncture, exposing the flammable electrolyte within the battery. This can quickly lead to a heavy fire. Short-circuiting can also occur within the battery if an anode/cathode separator is broken. Following this, heat is rapidly released, and the thermal runaway process is enabled.
- Spontaneous Combustion: This type of failure is possible in all batteries that are not maintained or monitored correctly. This can accelerate the thermal runaway process leading to a significant fire.
Electric Vehicle Safety Practices
As a result of the many unique failure mechanisms of an electric vehicle, multiple safety practices are required to ensure proper use and to reduce the risk of a catastrophic failure and/or fire. The following safety practices should be performed based on their corresponding failure mechanism:
- Over-Charging: To avoid over-charging, it is crucial to monitor the charging status of the EV and only use a charger designed specifically for use with the vehicle. Using a ‘smart’ charger can automatically stop charging once the vehicle is fully charged or reached a specific charge. This can be programmed to reach the desired charge level at a designated time. If an EV is not used for an extended period of time, avoid charging to full capacity. Charging to 80% is ideal.
- Charging Station Failures: Ensure all wiring at charging stations are undamaged and in good condition. Additionally, a supercharger should only be used periodically to maintain battery health. Vehicles should only be regularly charged with their recommended charging ports and amperage.
- External Heat Sources: Parking an EV in a shaded or covered area when it is not in use can significantly reduce the potential for an external heat source fire. The ideal storage temperature for storing EVs is between 15-25 C. It is recommended to avoid having an EV parked in direct sunlight for an extended period of time. Installing a sunshade can also help ensure the vehicle remains at safe temperatures if storing in shaded areas is unavailable.
- Physical Damage: If an EV is involved in a severe collision, the vehicle should not be operated. It should be turned off, and the fire department should be contacted as an ignition event is possible. The vehicle should be moved to an isolated area, away from people, buildings, and other vehicles. The manufacturer should be contacted for further instructions based on the circumstances of the collision and the associated damage.
- Spontaneous Combustion: The manufacturers’ instructions must be followed for charging and maintaining the EV. Avoid overloading the EV by carrying heavy loads, as this can cause the battery to overheat spontaneously. Regular maintenance, specifically to the battery, should be conducted to ensure all components are in good working condition. This can help identify potential fire-causing problems before they become serious.
As the transportation industry continues to rapidly transition to the regular use of electric vehicles, it becomes imperative that all new drivers know the unique hazards within their vehicles. Like all electrical devices, EVs are prone to failure if not correctly handled and maintained. Following the listed safety practices while understanding the unique failure mechanisms of electric vehicles will allow for the rapid increase of use within the industry as we transition away from fossil fuels and to a more sustainable future where electric vehicles dominate the transportation industry.
Sources
[1] https://www.goodcarbadcar.net/2022-us-vehicle-sales-figures-by-brand/
