Do Water and Electric Cars Mix? A Look at the Safety Standards & Fire Service Response to Emergencies

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By Pamela Coyle ~Coyle on Cars

We all remember parental warnings about mixing electricity and water. Those cautions are reinforced, at least in my case, by watching entirely too many accidental or homicidal death scenes on television that involve a small electric appliance and a bath, or in high-end settings, a hot tub.

Cars and water don’t mix well. I’ve managed to avoid driving through high floodwaters in both New Orleans and Nashville, but I’ve seen the results for those less fortunate. Inundated with cool water, hot engine blocks crack. The 12-volt electrical systems freak out. People get injured or killed – but by the water, not the electricity. And the carpet and upholstery never, ever recover.

The 2010 hurricane and flood season is upon us. The U.S. rollout of some high-profile EVs is nigh. And a question nags at me: What about the water?

An electric vehicle is not a toaster. Toasters, at least the ones we use at our house, do not have sophisticated automatic shut-off and safety systems, and EVs hitting the U.S. market later this year will. Keith Schultz, GM’s senior manager of Global Vehicle High Voltage Electric & Battery Safety, and Mark Perry, director of product planning for Nissan Americas, talked to me about electric power systems in the Volt and the Leaf, respectively.

The high-voltage wiring is under the car and not within the passenger cabin. In general, an impact automatically shuts down the high-voltage system that powers the car. Air bag deployment shuts 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.

Both General Motors and Nissan are providing information and training to emergency personnel in their EV target markets. The Volt training begins next month in Chicago during the International Association of Fire Chiefs Fire-Rescue International Conference.

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 differently than the familiar vehicle 12-volt batteries that power the lights, stereo and other auxiliary systems.

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. “Any loss of isolation, the battery sucks down and the control system will open the main contactors and contain the energy in the battery pack,” Mr. Schultz says. “If there is a crash, sensors also instruct the computer to open main contactors.”

These cars also have manual electric system shut-offs. In the Volt, a module attached to the battery pack is pulled out and separated. Access to a similar manual disconnect in the Leaf is through a panel in the floor, under a piece of carpet.

Mr. Perry of Nissan describes it as “three-layer protection.” The charging port has similar safeguards. “If damage to the port, then no power,” he says. And all major EV manufacturers have agreed to use a standard plug port.

High-voltage wiring also looks different. It is orange. This is not an arbitrary designer choice. Because electric vehicles are, well, electric, they must conform to electrical industry standards for wiring, and those rules dictate orange wrapping for the high-voltage stuff.

Gas-electric hybrids already follow these rules and carry some mighty powerful battery packs, ranging from about 150 to more than 300 volts of direct current. The danger zone for DC power can be as low as 55 to 60 volts, compared to 110 volts for alternating current.

EMTs, paramedics and firefighters are trained to recognize orange as high voltage. Should they need to cut the wires, labels with helpful icons that include a red fire helmet and pliers point the way in the Volt. The cut points also are wrapped in bright yellow tape.

EVs will 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, Mr. Perry says.

Safety is not a frivolous concern, and countering consumer misperceptions and wariness about new EV technology is part of the industry’s challenge. “A lot of myths out there we are trying to dispel up front so we can get ahead of it,” Mr. Schultz says.

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