University of Extrication: Low-Voltage Vehicle Batteries

Topic: Low-voltage vehicle power shutdown

Objective: The responder will understand vehicle 12-volt battery technologies and review their ability to accomplish power shutdown of a crash- or fire-damaged vehicle

Task: The rescue team shall update its protocol for accomplishing low-voltage power shutdown of a vehicle at an incident scene

When you are assigned the task of powering down a vehicle, there are several new technologies that you must know. Questions that must come to mind should include, “Where is the battery in this particular model?” and “How many batteries does this vehicle have?”

With crews reporting that the vehicle is initially stabilized and was placed in Park and that the ignition is off, your work outside to power down the vehicle can begin.

Key fobs

The popularity of key fobs is something newer that responders must know can be in the mix. Because many vehicles utilize key fobs as part of their starting process, manufacturers, such as Hyundai Motor Company and Mercedes-Benz USA, now recommend that the key fob be moved out-of-range prior to shutting down the power. This prevents an accidental restart of the vehicle while you work in, on and around it. Also, the systems of many vehicles that include a key fob automatically will lock all of the doors when the key fob goes out-of-range. Because of this, the doors must be unlocked and opened before taking control of the fob.

Locating the battery(ies)

To begin locating a battery, go to the front area of the vehicle. This still is the most likely location for a low-voltage battery, particularly in the case of an automobile that’s powered by an internal combustion engine.

If a battery isn’t found up front and you’re sure that it isn’t hidden under a panel or cover right where you are, go to the rear trunk or liftgate area of the vehicle.

Check along the inside of a rear fender well area or under the floor or spare tire well. Rear fender well areas are common places for automakers to mount a 12-volt battery.

If nothing is found front or rear, you must get your crew to join you in your 12-volt battery “Easter egg hunt.” This is no fun. The battery can be situated almost anywhere. Most likely it’s inside of the passenger cabin somewhere—for example, under a floor panel by the driver’s seat, front passenger seat or rear passenger seat.

As an example of the 12-volt battery being “hidden” inside, the low-voltage battery of several Mercedes-Benz SUV models is located beneath the floor in the floorboard area of one of the occupants of the vehicle. Numerous Volkswagen models have their battery under the driver’s seat. The low-voltage battery of older General Motors vehicles is beneath the rear passenger seat.

This author uses the Crash Recovery System smartphone app to immediately locate the battery on every vehicle that ever was sold in the United States. It locates the battery in about a minute and also indicates whether there are multiple batteries.

Multiple/auxiliary batteries

The possibility of multiple low-voltage batteries in one vehicle is a real concern because of increased electrical demands that are placed on vehicle systems and new start-stop technology, particularly when dealing with newer-model vehicles. We can be lulled into believing that the vehicle has only one 12-volt unit, because that’s what we remember from a recent crash response or that’s what we were told during our extrication training.

The 2010–2014 Mercedes-Benz C250 sedans have two batteries; one is labeled as the starter battery, and the other as the main battery. One battery is under the hood; the second battery is in the rear trunk area.

If an automobile has multiple 12-volt batteries, you won’t be able to shut down electrical power until you reach all of them.

Pause before shutdown

If you are at the low-voltage battery, it’s wise for you to realize that once you “kill” the battery, all of the electrical components that are in the vehicle might cease to function.

With your hand tools ready—but before you actually shut down the power—pause, advise other responders what you are about to do and check with them. This momentary verbal announcement about powering down gives the other responders a chance to stop you while they operate any electrically powered devices that might be beneficial for them or for the patient care and extrication processes.

For example, they might want to press an inside button and unlock all of the doors, lower all of the windows with one press of a switch, set the electric parking brake or unlock and open a rear trunk or liftgate. If conditions are stable inside and it’s safe to do so, operating electrical systems such as these might give the patient and rescuers more access and more room inside.

When you are at the actual battery and you decide that you are ready to shut down the power, you want to begin working with the negative, or ground, cables. You can disconnect them from the battery terminals, or you can cut the cables.

After taking care of the ground cables, you immediately work on the positive, or “hot,” cables. When you get done, no cables should be attached to the battery.

If you do decide to use a cable-cutting tool, you should cut the cable in two places, or double-cut it, to take a chunk out of it. The small gap that’s created ensures that the fresh cut ends won’t reconnect and establish electrical continuity while you and your crewmembers work on the remainder of your rescue and extrication tasks.

1st Responder Cut Label

An identifier that might be visible somewhere in or on the vehicle is a specially designed label that’s referred to as the “1st Responder Cut Label.” This label is a bright-colored sticker or shiny tag that identifies the cable (usually a ground cable, but not always) that the automobile manufacturer wants you to cut during the process of shutting down its vehicle’s low-voltage electrical system. The presence of cut labels usually means that the battery(ies) is buried somewhere on the vehicle in a way that makes it almost inaccessible for rescuers.

Cutting on each side of the cut label not only takes that label out of the way, but it also accomplishes double-cutting.

Realize that there can be multiple cut labels for a given model of automobile. If this is what you run into, you must cut each identified cable on each side of each label.

You might sense that after the battery and its cables have been dealt with, your powering-down work is done. Not so fast.

If you’re assigned to power down a crash-damaged vehicle, it’s your responsibility to ensure that the automobile’s power is actually and fully off.

A final and most important step in the powering-down process is one that often is forgotten: You must confirm that the vehicle truly is powered down. No lights should be on, and no sounds should be coming from the vehicle: With a door open, the dash and instrument panel should be dark, the dome light shouldn’t be illuminated, and the open-door buzzer shouldn’t be sounding.

If something still is lit up or still working, there might be another battery tucked away somewhere. Find what still is powering the system and get it taken care of.

48-volt electrical systems

The common 12-volt battery and 12-volt electrical system most likely will evolve to become a 48-volt battery that’s integrated into a 48-volt electrical system. This change to a higher-rated low-voltage battery will bring additional changes in your vehicle rescue protocol for power shutdown.

Automobiles that utilize 48-volt power already are on the roads, so now is the time to begin preparing to encounter them.