Isolate the Power

BY DAVID DALRYMPLE

Turn off the ignition. Remove the key to your apparatus. Discover and disconnect the vehicle’s 12-volt battery. Document these actions (photo 1).


1. Photos courtesy of author.

We all have heard this and have been taught it repeatedly. But how many of you and your crews do it regularly? Vehicle power is not your friend. It is even harder to isolate vehicle power today. We face numerous batteries, in different and unusual locations, and with unfamiliar configurations (photo 2). Additionally, vehicles have more power accessories than ever: seats, windows, doors, and hatches. Not only do we need to size up the vehicle quickly and comprehensively, but we also have to reposition power accessories and then isolate vehicle power.


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Why is power isolation so important today? Twenty years ago, power isolation wasn’t critical. However, with the advent of air bags and other vehicle safety systems, power isolation is now more complex. The brain of the vehicle supplemental restraint systems (SRS) includes power capacitors that store enough power to activate the system in case the battery is damaged in a crash. To drain those storage capacitors, we must disconnect the 12-volt battery.

Ignition. The first step is to locate the vehicle’s ignition and turn it off. Is the ignition a conventional key or a proximity key system? Although we usually think about an ordinary, conventional metal key, every year we see more and more vehicles with proximity ignition systems that are wireless and do not use a metal key (photos 3, 4). In some of these systems, the key itself does not need to be inserted into the dashboard or column; it just has to be within the confines of the vehicle. This means we might have to locate the key and secure it away from the vehicle (on the apparatus, perhaps) to ensure that the ignition is shut off and cannot be accidentally turned back on by the key. As a result, in today’s vehicles, this shuts the vehicle’s systems down and starts the drain time for the SRS energy storage capacitors—a good thing for us.


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Battery.Now, to ensure that we isolate power, we must locate the vehicle’s primary battery and disable it. Disconnect or cut the battery cables—both positive and negative. Although we might think this does it, it might not. Many vehicles today have multiple batteries, and some of them slave off each other. Also, other forms of power from other devices might “back surge” into the electrical system. Additionally, there can be static charge from a variety of sources, including our rescue tools as we work on the vehicle. After completing these procedures, document the action and time. This drains the energy in the SRS storage capacitors and in hybrid vehicles shuts down the high-voltage drive system and isolates the power of the high-voltage battery. The key thing to note here is that shutting down the ignition and disabling the 12-volt battery will shut down all hybrid vehicles, regardless of the manufacturer (photo 5).


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Locating the battery.Fine, you say. But the important issue is, where are the batteries? Remember this statistic: In more than 40 percent of today’s vehicles, the primary battery is outside the engine compartment. Think of that for a moment. If it’s not in the engine compartment, then more than likely the battery is in the trunk/cargo area in the rear of the vehicle or maybe inside the vehicle as well, or even in all three locations (photos 6, 7).


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Think about how this impacts rescue time, even if you know exactly where the battery is. Access to vehicle information on-scene, not just for those vehicles with SRS issues, is becoming more and more critical. Two helpful resources available to responders include Holmatro Rescue Equipment’s Rescuer’s Guide to Vehicle Safety Systems (Web site: www.holmatro-usa.com/rescue.htm) and the Moditech Crash Recovery System, a computer software database (Web site: www.moditech.com).

Two cAse studies

Let’s look at two recent incidents involving vehicle-power issues. Both occurred within the past six months, one at a training session in Europe and the other at an actual emergency in the United States. Both incidents involved vehicles with batteries in unusual locations; isolating them would require making space to create access in practice. Both vehicles were high-end with extensive and comprehensive occupant protection systems, and in both incidents the battery was not isolated.

The first incident occurred in Europe during an educational program in a controlled environment and involved a 2007 Audi Q7 SUV (photo 8). The students were attempting a side removal evolution, also called a B-post tear or maxidoor evolution. The students had forced the rear door latch, made a relief cut in the base of the vehicle’s B-post, and severed the top of the B-post. Using a power hydraulic spreader, the students spread the base of the B-post away from the rocker panel, and the relief cut in the base of the B-post started to widen.


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The wiring harness that ran into the B-post started to stretch and began to part. Suddenly, the door-mounted side-impact air bags on that side of the vehicle—front, rear, and side curtain—deployed. Although no one was injured, the tool operator was struck by two of the air bags and was quite stunned—not only by the incident but also by its rapid occurrence.

Now, where was this vehicle’s primary battery? Although this vehicle was a right-hand drive model, the battery is under the driver’s seat in both right- and left-hand drive vehicles (photo 9). The only accessible part of the battery was the negative terminal, which is not labeled or marked in any way. Accessing that one terminal requires removing the floor mat and pulling out the precut carpet section. Now, if you encountered this vehicle for the first time, would you have known where the battery was, and if you found it, would you have secured the power?


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In the second incident, a single-vehicle crash involving a 2007 Cadillac DTS occurred in the southeast United States. The vehicle hit a tree at a significant rate of speed and landed on the driver’s side. The tree intruded more than a foot into the vehicle and the vehicle was bent into a C, trapping the driver between the A-and B-posts. In this vehicle, the battery was under the rear seat.

On arrival, the crews found the driver heavily entrapped and began an extrication that lasted almost two hours. The only SRS that had deployed was the driver’s side side-curtain air bag. The crew performed patient management as the roof was removed using a roof trench evolution. During extrication, the driver’s seat back was removed, as was the passenger-side front door. The crew also attempted to displace the driver’s seat rearward but was unsuccessful.

To make space around the patient, personnel cut the steering wheel spokes with the power hydraulic cutter and removed the steering wheel ring. The crew also attempted to cut through the vehicle’s floor with an air chisel to facilitate seat displacement. During the floor cuts, the driver’s-side frontal air bag deployed, striking the firefighter who was providing patient care in the face and arm and knocking him completely out of the vehicle.

From the photos, would you have realized the battery was under the rear seat? Even if you did, would you have been able to access it (photos 10, 11)?


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Although both case studies are brief, I hope the photos have filled in any blanks. Consider the implications of these two incidents. We know it can be difficult to find batteries even in an undamaged vehicle. Add crash damage and, depending on where and how severe that damage is, the incident’s complexity is vastly increased.

Consider the tool evolutions described in both studies. Are they unusual or pretty much straightforward evolutions we all have done? In both situations, the battery was in places we would not consider “normal.” Can we ignore or minimize the importance of isolating vehicle power today? How about the redundancy in occupant safety systems, the complexity of vehicle electrical systems, and damage from a crash? And here we come with power hydraulic tools.

We are only seeing the tip of the iceberg just now. We need to aggressively mitigate vehicle hazards, whether at a motor vehicle crash, a vehicle fire, or even a medical emergency involving an occupant. We always need to err on the side of caution and protect our safety first and foremost.

DAVID DALRYMPLE is a 25-year veteran of the emergency services; an EMS provider for the Robert Wood Johnson University Hospital EMS in New Brunswick, New Jersey; and a rescue services captain for Clinton (NJ) EMS/Rescue. He is the education chair of the Transportation Emergency Rescue Committee-US (TERC). Dalrymple is certified as an international level extrication assessor and serves on the Expert Technical Advisory Board of the IETRI as road traffic accident advisor. He has taught and assessed in North America, Europe, the United Kingdom, and South Africa. He is also a member of the IAFC Specialized Technical Rescue Committee. He received the 2007 Harvey Grant Award for excellence in rescue. Dalrymple volunteers as a fire/rescue technician for the Sports Car Club of America-Northern New Jersey region and Rally America.

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