From the vehicle extrication e-Newsletter, sponsored by
Article and photos by Jason D. Emery, Emergency Training Solutions
Although hybrid vehicles can present significant hazards to emergency response personnel, proper education and strict adherence to standard operating procedures can alleviate these dangers. This article highlights two primary concerns of hybrids: the high-voltage electrical system and the potential for unexpected vehicle movement.
The high voltage batteries in hybrid vehicles range from 144 to 330 volts DC. Some manufacturers, such as Toyota, Lexus, and Nissan, use power converters to increase the operating system voltage to 650 volts AC to power the electric drive motors. Contact with these high-voltage systems during extrication or other emergency operations can result in serious injury. Emergency personnel should never attempt to cut or disconnect any high voltage wiring. In the event of a collision, hybrids have several safety features designed to shut down the electric system. Likewise, if the electrical wiring were to come into contact with the chassis, it would create a short and the system fuse would cut high-voltage power. Even with proper disabling techniques, always assume that the system is still energized.
The second danger is the lack of an outward sign indicating a vehicle’s ignition is engaged when it is in “ready” mode (Photo 1). Unlike traditional vehicles, hybrids have the ability to shut down their gasoline engine and start it instantaneously when it is needed. Some hybrids can use their electric motors to move silently at speeds up to 20-25 mph. Emergency responders must approach the vehicle only from the sides, never in a potential path of travel such as front or rear. Most hybrids have some type of indicator on the dash to indicate the vehicle is in its “ready” mode. This issue typically presents a more prevalent hazard to responders than the high-voltage electrical because of the electrical system safety features, and because the majority of motor vehicle accident (MVA) responses do not involve extrication operations.
Photo 1
Photo 2
Once an approach to the vehicle has been made, make sure to chock the wheels, place the vehicle in Park, set the emergency brake, and ensure that the ignition is turned off. At this point, disconnect the 12-volt battery to further secure the vehicle systems (Photo 2). By taking these basic steps, you have secured the vehicle from potential movement, shut down the occupant protection systems, and disengaged the high-voltage electrical system.
Photo 3
During extrication operations, there is little difference between a response to an incident involving a standard vehicle and one that is a hybrid. Although high-voltage wiring is not found in typical cut points, care must be taken during extensive extrication operations to avoid high-voltage wiring. The cable is typically bright orange (Photo 3), although some hybrids have blue cables to indicate a medium-voltage system. Wiring may be covered by black plastic and not be readily visible. (Photo 4)
Photo 4
Use caution when operating around a damaged high-voltage battery. Although the potential for electrolyte release is minor, it is still damaging to human tissue. The other concern is the electrical charge; even with a disabled high-voltage system, the battery still retains stored power.
Although hybrid vehicles do present some obstacles for emergency responders, the implementation of a full training program and a standard operation procedure will minimize those concerns and bring everyone home safe at the end of the day.
Jason Emery has been with the Waterbury (CT) Fire Department for 13 years and is currently assigned to city’s Rescue/Hazmat Company. He is an 18-year veteran of the fire service, a certified fire instructor, and holds a bachelors degree in fire science from the University of New Haven. He is the founder of Emergency Training Solutions, LLC. He can be reached at jason@etsrescue.com.
