Everything you need to know about the safety of an Electric vehicle
EV safety is guaranteed by technological advancements and stringent regulations enforced globally and in India
Crash Safety: EV battery comes with a strong protective casing which makes it safe during a Crash
Fire Safety: Thermal stability of EV is maintained by cooling & battery chemistry improvements
Electrical shock safety: Advanced multi-layer insulation, waterproofing & stringent regulatory standards ensure EVs are safe from Electrical shocks
💥#1 Crash Safety
Active safety features help prevent accidents. EVs are less prone to accidents, hence EVs score high on Active safety.
In an electric vehicle, the battery is the heaviest component and since batteries are placed beneath the floor, centre of gravity of an EV is lower than a petrol/diesel car. It serves as an inbuilt safety system and makes EV quite stable while driving and cornering.
In EVs the ability to control torque at each of the wheels is far more precise, this helps to reduce tyre slippage and hence the number of accidents
EV vehicles are heavier than conventional Petrol / Diesel cars, which leads to higher kinetic energy. This challenge is addressed by tuning the active safety features like ABS - Anti-lock braking system, ESP - Electronic Stability program, etc to suit the requirement
Weight distribution of Electric vehicles is nearly uniform across the front and rear axles compared to heavier front axle load on petrol cars, this helps EV to remain stable during hard braking.
Passive safety features help save the occupants after the accident.
Electric vehicles go through similar crash safety tests like ICE (Internal combustion engine) cars. Viz. Frontal Crash, Front offset, and Side impact. The most important EV component which needs to be protected in the event of a crash is the battery box.
Different OEMs address this issue differently,
a) Polestar: Polestar, the brand owned by Volvo cars have designed a SPOC Block specifically to minimize the intrusion of the wheel, tire, and other objects towards the battery pack
b) Tesla has securely encased the battery box in a crash-proof steel box that can withstand front, side, and rear impacts. This reduces the damage to battery components and hence avoid spillages and fire
In addition to the above, the absence of a heavy mass, viz. engine, in the front improves the functional crumple zone of the electric vehicle. This helps to avoid rupture of the firewall/bulkhead into the passenger compartment improving the safety of the occupant
🔥 #2 Fire Safety
Preventing fire hazard:
Lower Flammability: Electric vehicles are safer than ICE vehicles due to the lower flammability of Li-ion batteries.
Battery Chemistry: Battery cells have separators between Anode and cathode, these separators are coated with select inorganic materials to enhance the thermal, mechanical, and electrochemical performances of the battery.
Cooling: Most automakers have shifted to liquid cooling technology to keep the temperature of the battery, motor, and power electronics in a safe operating temperature range.
Test: Batteries undergo the following abusive test to ensure they are safe from any fire hazard:
The probability of an EV catching fire is lower than cars with internal combustion engines (ICE). According to the Fatality Analysis Reporting System, the fire was found in 2.6% of EVs and 4.4% of ICE vehicles, in cases of fatal vehicle crashes. These cases were analyzed in the US from a database of 60,000 annual crashes.
Post Fire safety:
In case of an unfortunate fire incident, Gasoline fires start almost immediately and spread rapidly. Whereas EV Battery fires typically take some time to achieve the heat necessary to start the fire. That delay can let the occupants of an EV to get out of the vehicle in-time.
Tesla provides an extra aluminum plate for fire protection between the battery pack and passenger compartment. Though not mandatory, it helps to keep the vehicle safe.
⚡#3 Electrical shock Safety
Electric vehicles operate at a very high voltage compared to petrol/diesel cars. ICE cars run on a 12V battery system, whereas electric vehicles operate at a voltage band of 400 to 800V. To ensure safe operation and handling of electric vehicles, the high voltage cables and connectors are protected with multiple layers of shield and insulation.
In the event of flooding:
The electrical components in an EV are well protected to avoid dust and water ingress, the regulatory standard which ensures ingress protection is called the IP standard. EVs need to clear IP67 certification before they can be sold. IP67 protects electrical components from dust and water ingress up to 1-meter depth. OEMs do extensive validations including 'water wading tests' to ensure IP compliance. Below image demonstrates a Nexon EV undergoing the water pond test
In the event of damage:
Electric vehicle batteries are connected to the Motor through a secure connector. This connector is switched ON/OFF via a pyrofuse attached to the battery box. This pyrofuse or battery disconnector helps isolate the battery box from the rest of the vehicle during an accident, this way both the occupants and rescuers remain safe from any electric shock post the accident.
Pyrofuse is a semiconductor device which “blows out” the cable connection to the high-voltage battery by means of a miniature explosion, thereby quickly and effectively shutting off the power circulation. This way pyrofuse eliminates the risk of electric shock or fire post-accident.
Charging cables and the charging stations are water-proof and are fully insulated from any electric shock. Plus features like undercharge and overcharge protections add to the safety. Charging connectors also come with a theft-proof lock mechanism, which prevents anyone from disconnecting the cable from a vehicle while charging.
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Team "EV Quotient"
(EV Quotient is a platform to discuss and learn about electric vehicles. It’s an initiative by a team of experienced Automotive professionals with Global Exposure)