How safe are the high-voltage electrical systems that power electric cars? What happens should they become immersed in water, which is a very real possibility during hurricane and flood season?
As GM and Nissan launch their EV’s, this is a real safety concern for potential consumers. Although the Volt has a small internal combustion engine that keeps the battery charged longer, both it and the Leaf incorporate high-voltage power that is engineered very differently than the familiar 12-volt battery that power the lights, stereo and other auxiliary systems in gas-fueled vehicles.
A jolt from a 12-volt can give you a bad buzz. An electric shock from a damaged high-voltage EV can kill, or can ignite stray gasoline. A regular car battery produces shocks because it is not a closed system and is grounded in the vehicle structure itself. In an EV, the electrical system is isolated and self-contained in its own circuit.
To mitigate the possibility of electrocution, GM and Nissan have installed the high-voltage wiring under their EV’s and not within the passenger cabin. In general, an impact automatically shuts down the high-voltage system that powers the car as the deployment of the airbags shut it down. The battery pack itself is completely sealed. Any loss of isolation within the electrical system shuts it down. A manual shut-off exists for first responders who may worry that the juice is still flowing.
In addition both General Motors and Nissan are providing information and training to emergency personnel in their EV target markets.
EV’s face the same federal standards for crash testing and the manufacturers have put the battery packs through some special ordeals to test their integrity. At Nissan, for example, engineers have dumped the battery pack into swimming pools, frozen it and hit it with high-pressure hoses.
Public safety is not a frivolous concern and countering consumer misperceptions and wariness about new EV technology is part of both the government’s and the car industry’s challenge.
So the bad news is that floodwaters can still quickly consume a vehicle and its occupants. The medium news is that it doesn’t much matter how the vehicle is powered. The good news is that the weight and location of battery packs may give EVs an edge because they create a lower (and heavier) center of gravity but also permit ground clearance that is higher than a typical sedan and closer to that of an SUV.
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