By JASON EMERY, KEITH SCHULTZ, and CHRIS PEPLER
Emergency responders will begin to respond to more crashes involving electrically propelled vehicles, such as the Chevrolet Volt, highlighting the need for firefighters to learn more about how electric vehicles function and the necessary response procedures. Fortunately, many of the principles and procedures that responders have learned previously for hybrid electric vehicles also apply to the Volt. This article focuses on the Volt, its systems, and emergency response procedures.
The 2011 Chevrolet Volt (photo 1) was launched in select U.S. markets (including Los Angeles, San Francisco, Austin, metro New York City, and metro Washington DC) in November 2010 and is the first of a new generation of electric vehicles (EVs) with extended range capability. The Volt was released across the United States in 2011.
|(1) Photos by author unless otherwise noted.|
The Volt has several external and internal features that will aid first responders in identifying the vehicle. On the front fenders (photo 2) and on the rear hatchback (photo 3), the “Volt” badging is clearly visible. The vehicle’s charging port can be found behind an access door on the driver’s fender directly underneath the Volt badging (photo 4).
The vehicle’s interior can also provide some identification clues. The instrument panel area presents two digital display screens. One is the digital instrument cluster, which can be found directly in front of the driver behind the steering wheel. The other is the energy/audio system display found in the center of the dashboard (photo 5). Each display screen contains features indicating that the vehicle has a high-voltage system, such as an indicator for the level of charge in the high-voltage battery. The Volt is a four-passenger vehicle that features two bucket seats in the rear instead of a standard bench seat to accommodate the propulsion battery under the floor. Since this is not a common feature in a sedan, it can be a helpful visual indicator that the vehicle is actually a Volt.
Under the hood you will see the engine/generator and high-voltage electrical components including the industry standard orange-colored high-voltage wiring (photo 6). You will also find warning labels marking the locations of high-voltage components. In addition, there is a warning label that shows the location of the high-voltage battery, the 12-volt (v) battery, and the recommended 12v power cut point (which will be addressed later).
An additional means of identification is available through the integrated OnStar® system. The 2011 Volt is sold with a five-year subscription to the OnStar service. In a crash that activates the Automatic Crash Response system, the appropriate jurisdiction’s dispatch center will be notified not only of the crash but also of key information such as the potential extent of injuries and, most importantly, the fact that it is an EV. Over the next few years, the use of telematic systems such as OnStar and others will become more popular in vehicles and will help notify responders of incidents involving these vehicles.
The Volt is essentially built around its high-voltage battery, which is under the center of the vehicle and underneath the rear seats in a “T” shape configuration. The vehicle incorporates a great deal of high-strength steel into its structural design. Although the use of high-strength steels in vehicle construction is becoming more prevalent, the Volt’s frame consists of approximately 80-percent high-strength steel (photo 7), one of the highest percentages in the industry. This provides optimum protection for all the occupants as well as the high-voltage battery.
|(7) Photo courtesy of General Motors.|
Although it may appear that the high-voltage battery sits within the passenger compartment, it actually sits on a metal tray mounted to the bottom of the vehicle. The vehicle floorpan is also constructed of high-strength steel, providing a barrier between the high-voltage battery and the occupant compartment. Recent updates to the Volt’s design include additional reinforcement around the high-voltage battery to provide an increased level of protection for side impact crashes.
Although the use of high-strength steel provides an increased level of protection for the occupants, it can present an obstacle to rescuers using older or smaller hydraulic tools to cut through the vehicle structure such as the roof posts. It is highly recommended that if you are unsure of the capabilities of your equipment, you should contact your tool vendor to make that determination. Realizing your cutting tool is outmatched in a 2:00 p.m. phone call is better than finding out at a 2:00 a.m. crash scene. This concern about high-strength steel usage is not, however, limited to just the Volt. The use of high-strength steel has increased in a large variety of vehicles and will continue to do so in the future. As this is becoming a greater issue in extrication operations, firefighters are urged to seek additional training and information on the subject. Additional information on this topic can be found from a variety of sources including www.boronextrication.com.
OCCUPANT PROTECTION SYSTEMS
The Volt is equipped with dual seat belt pretensioners for the driver and front passenger and a total of eight air bags standard. Air bags around the vehicle consist of frontal, knee, and thorax bags for each front seat occupant as well as head curtain air bags that deploy from the roof rails on both sides of the vehicle.
The frontal air bags are a dual-stage design and work in conjunction with the knee bags to protect the head, chest, and lower extremities. The thorax bags are mounted in the outer side of the front seats; the head curtain bags are mounted along the roof rail from the A post to the C post with a compressed gas inflator located in the C post. As on any vehicle, before any cutting operations begin, always use the “pry and peek” approach by pulling back interior trim and inspecting the area to ensure there are no occupant protection systems or other components that may pose a hazard during extrication. The seat belt pretensioners are outboard of the front seats only. They are pyrotechnic devices; avoid cutting through them.
HIGH-VOLTAGE ELECTRICAL SYSTEM AND BATTERY
The Volt is considered an EV with extended range capability. It is propelled by the electric drive unit, which is powered by either the high-voltage battery or the engine/generator (when in extended range mode). The estimated range of this vehicle when using the high-voltage battery is approximately 25 to 50 miles on a single full charge, depending on driving conditions. The Volt has an additional feature incorporated into its design that gives it extended range capability. There is a 1.4-liter engine/generator under the hood designed to automatically turn on to produce electricity and run the electric drive unit motors should the battery charge become depleted. The engine/generator is not designed to recharge the battery but to produce electricity so that the Volt can travel an additional 344 miles before needing to be recharged.
The high-voltage battery can be recharged only using an external 120v or 240v power source. For an emergency responder, this makes the vehicle similar in response concerns to a hybrid; it contains both high-voltage electricity and gasoline. The gasoline tank holds 9.3 gallons and is behind the T-shaped propulsion battery. The battery is 5½ feet long × three feet wide, weighs approximately 400 pounds, and consists of three sections notched near the center to allow a cross car structural member to run through it, providing additional lateral stiffness during a crash. It is comprised of 288 Li-Ion cells, which produce a nominal battery voltage of 360v, just slightly higher than what some hybrids currently operate at (photo 8). The individual cells are heated or cooled using propylene glycol (antifreeze) flowing through the battery. This keeps the cells at a safe operating temperature to maximize energy usage and battery life.
|(8) Photo courtesy of General Motors.|
If the battery case becomes damaged in a vehicle crash, you may see reddish fluid leaking out. This is not battery electrolyte but the antifreeze material used to regulate the temperature in the battery and gasoline engine/generator. Battery recharging is through the use of a Level I (120v) or Level II (240v) charging station. From a fully depleted battery, it takes approximately eight to 10 hours to fully recharge using a Level I charging station and three to four hours using a Level II charging station.
Other key components of the electrical system include a direct current (DC) to alternating current (AC) converter, which takes DC power from the high-voltage battery and converts it to AC power to drive the electric motors. This inverter module is under the hood (photo 9). There is also a DC to DC converter called the Accessory Power Module (APM), which is under the rear cargo area of the vehicle. Since there is no alternator in the Volt, the 12v power to run the vehicle’s standard 12v systems and to charge the 12v battery comes from the high-voltage battery. This high-voltage power is stepped down to 12v by the APM.
It is more critical than ever that responders take the time to identify the types of vehicles involved in a crash. You can no longer take for granted that you are dealing with vehicles with standard internal combustion engines. As green technologies become more popular, the frequency that responders will encounter incidents involving alternative fueled vehicles, such as HEVs or EVs, will undoubtedly increase. The best thing to do is assume that you are dealing with such a vehicle until you either confirm or rule it out.
Controlling hazards. As with any vehicle, your first priority is securing it from potential movement. Do this by chocking the wheels, accessing the passenger compartment to set the parking brake, placing the vehicle in park, and shutting down the vehicle’s ignition system. Shut down the Volt’s ignition system by pressing the power button found just above the gear selector (photo 10) in the center of the instrument panel. Note that the Volt is equipped with a proximity key; if possible, remove it from inside the vehicle as part of the shutdown procedure. Keep in mind that the key may be difficult to locate, depending on the driver’s condition and his ability to communicate with responders. However, once the 12v power has been properly disconnected, there is no way for the vehicle to be turned back on, even if the proximity key is still in the car and the power button is pressed again.
After completing the ignition shutdown process, ensure the shutdown of the vehicle’s 12v electrical system. As with other EVs and HEVs, the 12v system controls the high-voltage system. By removing the 12v power, the battery’s relays, which allow the high-voltage current to flow through the vehicle, are opened and the circuit is broken. In the Volt, this is accomplished by using the special cut location provided in the rear of the vehicle. On opening the rear hatchback, an access panel can be on the driver’s sidewall of the cargo area. This access panel displays a logo of a firefighter’s helmet to indicate its purpose (photo 11). Behind the access panel you will notice a bundle of wires in a black wrap with GM’s “first responder yellow cut tape” attached to it (photo 12). Make two cuts, one on either side of the yellow cut tape, to take a section of the cable out. By cutting in this designated location, you isolate both sources of 12v power—the 12v battery and the APM—from the relays in the high-voltage battery. This is designed to ensure that the relays discussed earlier open and break the circuit. Also be aware that this designated cut point actually severs the 12v positive cable rather than the 12v negative cable. Although we have always been taught to first disconnect or cut the negative side of the battery, it is necessary to cut the positive side in this application to cut off both sources of 12v electricity.
Extrication. As with hybrid vehicles, there are no specific techniques used for extrication operations because the high-voltage orange cabling is routed in areas not traditionally considered vehicle cut points. It is important, however, that extrication personnel inspect the area they are cutting to ensure that they are not cutting through any high-voltage components. This visualization process is also important on conventional vehicles because of increased use of occupant protection system components such as stored-gas air bag inflators, which are placed in various locations. The days of blindly cutting through vehicles has long passed.
The key issue that responders must contend with during extrication is the extensive use of high-strength steel. As mentioned previously, the Volt’s structure, which includes the occupant safety cage, is comprised of approximately 80-percent high-strength steel. Responders need to be aware of their rescue tools’ ability to cut through these materials and should contact their local dealer or manufacturer representative to make that determination. The use of high-strength steel is not limited to the Volt and has been used on many different vehicle platforms in recent years. Its use, however, is becoming more common, and responders will begin to encounter it with more frequency.
There are various workaround methods available to responders should their tools prove incapable of cutting the high-strength material. For example, if your cutters are unable to get through the post material when attempting to remove a Volt’s roof, the fastest way to provide nearly the same level of access is to remove the center area of the roof using a reciprocating saw. Since there are no high-strength steel components running across the roof between the roof rails, you can make a cut inboard of each roof rail from the rear hatchback down through the windshield to remove the entire middle section of the roof.
Submerged vehicle. You can safely operate around a submerged Volt in the same manner that you would a conventional vehicle or a hybrid. The vehicle’s electrical system is not going to energize the water surrounding the vehicle; it is safe to open the doors to access the passenger compartment. Also, since the high-voltage system is designed to be independent of the vehicle chassis, the exterior of the vehicle is safe to touch. Should the normally isolated high-voltage circuit come in contact with the chassis, the fuse in the high-voltage circuit is designed to open and shut down the high-voltage system.
Vehicle fires. Traditional firefighting equipment and techniques are acceptable to extinguish a Volt that is on fire. As with conventional vehicles, firefighters should use full personal protective equipment and self-contained breathing apparatus to protect themselves from thermal injury as well as from inhaling any toxic substances produced by the burning of vehicle components. GM recommends the use of copious amounts of water during extinguishment operations, especially if the high-voltage battery is on fire. Should the high-voltage battery catch on fire, testing has shown there is no danger of explosion. The electrolyte in the battery cells is flammable and will burn rapidly when exposed to flame. Since both the DC and AC found in these systems do not have an earth ground reference, firefighters can safely use water as a primary extinguishing agent without a risk of electrocution. Firefighters should avoid direct contact with the inside of any high-voltage component during firefighting or extrication operations; this would potentially result in an electrical shock.
The Volt is considered the first of many entrants into the EV market. It can be identified using the Volt logos as well as other key features on the vehicle such as the external charging port on the driver’s side. As with any vehicle, be sure to immobilize the Volt on approach by chocking the wheels before you begin the shutdown procedure. In addition to your shutting down the vehicle’s ignition system, GM has provided responders with a location to disable the vehicle’s 12v system. This designated cut point is behind an access panel on the driver’s side of the rear cargo area.
Firefighters and other first responders must ensure that they understand the technology and operation behind EVs and HEVs. Those individuals with prior training on HEVs will find that many of the basic operating principles are similar to those for EVs. Follow the principles of identify/immobilize/disable when dealing with EVs and HEVs to ensure your safety and the safety of your crew.
For more detailed training on the Chevrolet Volt, access GMs online training program developed by the National Fire Protection Association (NFPA) at www.evsafetytrainining.org. Additional information about responding to crashes involving the Chevrolet Volt can be found in the Emergency Response Guide at www.gmstc.com. GM will continue to refine first responder training information for its vehicles as it works with the NFPA on research projects and participates with other vehicle manufacturers through recognized industry forums such as the Society of Automotive Engineers.
JASON EMERY is a 21-year fire service veteran and a lieutenant with the Waterbury (CT) Fire Department assigned to the Rescue/Hazmat Company. He has a B.S. in fire science from the University of New Haven and is a member of the International Society of Fire Service Instructors (ISFSI). Emery has lectured throughout the country on the subject of electric vehicles (EVs) and hybrid electric vehicles (HEVs), including the past four years at FDIC. He is a subject matter expert and development team member for the National Fire Protection Association (NFPA) and the lead instructor for its Hybrid and Electric Vehicle Training program.
KEITH SCHULTZ is a 27-year employee and manager of vehicle technology and safety policy at General Motors (GM). He has developed high-voltage safety strategies for future HEVs and battery systems for the GM Global Electrical Systems group. His contributions on the Global Vehicle Integration Electrical Safety Team helped establish high-voltage safety requirements, policies, and best practices. He has a B.S. in mechanical engineering from the University of Cincinnati and a master of science in mechanical engineering from the University of Michigan.
CHRIS PEPLER is a 21-year fire service veteran and a member of the Torrington (CT) Fire Department. Pepler is a certified fire instructor for the International Society of Fire Service Instructors (ISFSI) and the Connecticut Fire Academy and is an assistant director for the Wolcott State Fire Training School. With the NFPA EV Safety Training program, Pepler has lectured with the Chevrolet Volt training team to first responders across the country and is an instructor for its EV Train-the-Trainer program.
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