How Safe are Electric Vehicles?
In March this year, Federal regulators in the US proposed the introduction of new protective measures to prevent drivers of electric vehicles (EVs) from suffering an electric shock. According to the Transportation Department’s National Highway Safety Administration (NHTSA), the measures are intended to prevent drivers from suffering harm in the event of crashes and during everyday operations such as charging the car. These requirements would also extend to emergency services personnel attending the scene of accidents.
This might seem as if there is some special risk associated with green vehicles, but actually, according to the Department of Energy’s Alternative Fuels Data Centre (AFDC), green vehicles are much like any other vehicles as far as maintenance and safety is concerned, although electric vehicles (EVs) generally have fewer maintenance requirements than hybrid electric vehicles (HEVs) or plug-in hybrids (PHEVs).
This is because HEVs and PHEVs retain internal combustion engines, while EVs operate off the battery, motor and associated electronics which require little to no regular maintenance. EVs don’t have that many fluids and brake wear is reduced significantly, thanks to regenerative braking. Furthermore, there are far fewer moving parts in an EV than there is in a conventional vehicle.
EVs are fitted with advanced batteries, usually of the lithium-ion type. These batteries have previously made their appearance in a smaller form in portable consumer devices such as mobile phones and laptops. Compared to other batteries and storage systems, they have a high energy per unit mass and a high power-to-weight ratio. They are very energy efficient and have a really good high-temperature performance with a low self-discharge rate. Most of them can also be recycled.
Nickel-Metal Hybrid batteries have also been fitted into EVs and they are also used in computers and medical equipment. They tend to be more widely used in hybrid electric vehicles. Compared with lithium-ion, they have a high rate of self-discharge, are quite costly and tend to generate heat at high temperatures.
The electrical systems in HEVs, PHEVs, and EVs are high-voltage, ranging from 100 to 600 volts. The batteries are encased in sealed shells. In the US, EVs have to meet Federal Motor Vehicle Safety Standards and they are subjected to rigorous safety checks, including tests that subject the batteries to overcharging, vibration, extreme temperatures, short circuits, humidity, fire, collision and water immersion.
The vehicles are also fitted with insulated high-voltage lines and there are safety features that deactivate the electrical system in response to a collision or a short circuit. One of the most important advantages of EVs, compared to many conventional vehicles, is that they tend to have a lower center of gravity, and that means they are less likely to roll over in an accident. They also have cut-off switches to isolate the battery and disable the electric system. The high-voltage power lines are instantly identifiable because they are all colored orange.
In recent years there have been concerns about magnetic fields emanating from EV electric systems. Unsurprisingly, given the number of conspiracy theories floating around the internet, these worries began appearing online the moment the first EV rolled off a factory production line. The major fears concerned the proximity of electrical systems to the vehicle occupants with references to previous studies on electromagnetic fields (EMFs) linking them to potential cancer risks, miscarriages and a higher occurrence of leukemia in children.
In 2008, Jim Motavalli wrote a report for the New York Times pointing out that these fears do indeed have a certain legitimacy, acknowledged by the National Institutes of Health (NIH) and the National Cancer Institute (NCI). However, much of the clamor about possible risks in EVs were generated by drivers taking their own readings with widely-available field strength detectors. Experts largely denounce such readings on the basis that ‘homemade’ assessments such as this are highly unreliable and inaccurate.
Then there are the people who announce their own version of ‘wind turbine syndrome’, claiming the electrical systems in EVs have made them ill. One complaint was made by a woman who employed a ‘wellness consultant’ to take a reading from her car using a Trifield meter, a device manufactured by AlphaLab in Salt Lake City. The gadget is generally used to detect electromagnetic fields from alternating current (AC), but the systems used in EVs are mostly direct current (DC).
Another EV driver tried to alert Honda to the problem, but Honda responded that all their vehicles are tested rigorously and that people conducting home tests mostly use the wrong type of equipment. In another statement, Toyota said that electromagnetic fields in its hybrid vehicles are more or less the same as those in its conventional vehicles, meaning that there are no additional risks to occupants of EVs or hybrids.
These fears concerning EMFs have recently provoked a study by Sintef, based in Norway, which has quickly dismissed such notions saying that they have been blown out of proportion. The tests focused on seven models of electric car, one hydrogen fuelled car, two petrol cars, and one diesel car. They were carried out in both laboratory conditions and during road tests. The research found that the highest EMF exposure came from the floor when starting the vehicle and also at a point close to where the battery is located. In all tests, the results were lower than 20 percent of the value recommended by the International Commission on Non-ionising Radiation Protection (ICNIRP).
It is also worth bearing in mind that EV models have many of the standard safety features fitted to conventional vehicles, such as ABS brakes, electronic stability control, pre-tensioning seatbelts, and airbags. Another common feature in EVs is the noise generator, which, in the absence of a noisy conventionally fuelled engine, generators noise to warn pedestrians when an EV is approaching.
Finally, there is the fear of ‘battery fires’ focusing on lithium-ion batteries. This kind of reports began to emerge several years ago when some lithium-ion batteries in laptops and mobile phones caught fire. The potential risk here concerns the high energy density of the battery, given that there is a huge amount of power contained within a relatively small area. This, in turn, carries a risk of overheating.
However, the good news is that EV manufacturers have compensated for this by cramming cars with all sorts of preventative technology, such as the fuses and circuit breakers previously mentioned that can disconnect the battery when sensors fitted to the car detect a collision is about to take place.
Other measures include coolant systems, such as the radiator-chilled coolant used by Tesla in its battery pack. This keeps the temperature as low as possible while the vehicle is running. Other manufacturers, such as Nissan in its popular LEAF model, use an air-cooling system. Another tactic is to locate the battery pack in the center of the car, underslung on the bottom of the chassis and away from the crumple zones at front and rear.
All that makes EVs very safe indeed, and certainly a lot safer than a conventional tin can with a load of petrol sloshing around.