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SUBJECT: Hybrid Vehicle Update 2007 — Part 2
TOPIC: Safety Considerations at Gasoline-Electric Hybrid Vehicle Incidents
OBJECTIVE: Understand unique safety considerations involving specific 2007 hybrid vehicles mentioned in this update article
TASK: Given the specific hybrid vehicles mentioned to review and examine, the rescue team shall identify the components presented and shall develop operating guidelines for dealing with specific hybrid-vehicle challenges.
This University of Extrication column serves as an update on important design and operating features of several 2007 and 2008 model-year gasoline-electric hybrid vehicles.
GM's Saturn Division has introduced its Green Line hybrids, which include the 2007 Saturn VUE and the 2008 Aura. Both hybrids have a 36-volt hybrid electric system integrated into the gasoline-powered vehicle. The Saturn VUE is an SUV while the Aura is a sedan.
These hybrids use the color blue for their 36- to 42-volt wiring. Although there is no standard color-coding policy in the United States for hybrid-vehicle high-voltage wiring, General Motors has decided that blue is an acceptable color for what it classifies as these "intermediate" voltages. All hybrid-vehicle manufacturers route their high-voltage cables beneath the floorpan of the vehicle, out of the interior occupant area. On all other hybrids, however, the cables are color-coded "traffic cone" orange as they run beneath the vehicle. Be alert and be aware with the VUE and the Aura.
Our second safety challenge with these two new GM hybrids also involves the blue HV cables. The bright-blue cables carry a lower DC voltage after any airbag has deployed or the hybrid has been involved in a rear-end collision. What is even more important is that by either turning off the ignition or disabling the 12-volt power at the battery, the responder has only reduced the 36-volt current flow to an "acceptably low level" in the blue cable. In other words, that blue cable in the engine compartment and the same blue cable running beneath the vehicle inside the metal conduit still remains energized after a crash. It is not this way with any other manufacturer's hybrid vehicles.
All that GM safety personnel can say is to not cut the blue intermediate voltage (36-volt) cable because there is a higher arc potential. For these hybrids, we must access the actual high-voltage battery in the trunk or rear storage area and remove a black metal cover. As the cover opens, a spring-loaded button pops out. That button is the main disconnect switch for the high voltage and will shut down the current at the 36-volt battery. Once again, be informed and be aware!
One additional safety challenge with these two GM hybrids is that their standard 12-volt battery in the engine compartment is completely hidden beneath a large component called the ECM. The ECM, or engine control module, is covered by a large grey plastic shroud that has the word "HYBRID" printed on it. This gray cover has to be lifted off first.
Cover removal reveals the battery, but responders will also find that although there are two negative ground cables, one is almost completely obscured and the positive cables are not visible. GM engineers recognized how significant of a challenge this battery cable location will be for rescuers. In the emergency response guide produced for both these GM hybrid vehicles, the recommendation is to actually disconnect or cut a bare metal tab-type bracket along the top edge of the battery to shut down the 12-volt electrical power. The lower ground cable is all but impossible to access during a real-world incident, but is connected to this common point.
RON MOORE, a Firehouse® contributing editor, is a battalion chief and the training officer for the McKinney, TX, Fire Department. He also authors a monthly online article in the Firehouse.com "MembersZone" and serves as the Forum Moderator for the extrication section of the Firehouse.com website. Moore can be contacted directly at Rmoore@firehouse.com.