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Part 1 of this series familiarized responders with the Mitsubishi i-MiEV vehicle – a plug-in electric vehicle (EV) equipped with a high-voltage lithium-ion battery. In this University of Extrication column, we will describe a recommended shutdown process specifically when working on an electric plug-in vehicle. The seven steps of the Electric Vehicle Lock-Out/Tag-Out procedures are as follows:
1. Identification of vehicle as EV
2. Stabilize: chock/block
3. Access interior
4. Place vehicle in “Park”/set parking brake
5. Turn ignition OFF
6. Check instrument panel lights/indicators
7. Shut down 12-volt electrical system
In the scenario we will use for this column, responders find a crash-damaged electric vehicle that needs to be powered down. Following our seven-step recommended Electric Vehicle Lock-Out/Tag-Out procedures, once the vehicle is identified as an electric vehicle (Step 1), responders quickly chock or block the wheels (Step 2). With wheels chocked, one responder will then access the interior of the vehicle, either through an already open door or a window (Step 3).
Once inside, the vehicle transmission is placed in the “Park” position and the emergency brake is set if these actions are possible (Step 4). Now, with these steps accomplished, the ignition is turned OFF (Step 5). The Mitsubishi i-MiEV being used for our research is equipped with a typical ignition key. Once turned off, the recommendation is to place the ignition key on the dash to signify that the ignition has been turned off. Instead of an actual key, the inside rescuer may encounter a keyless ignition system. With these systems, turning the ignition off is accomplished by pressing the Power or Start/Stop button located on the instrument panel to the right side of the steering column.
Once the ignition is being turned off, the inside rescuer should immediately see something change on the instrument panel (Step 6) – a light will go out, a needle on a gauge will drop, an indicator will dim, etc. At this point, most of the shutdown procedure has been accomplished, but we are not finished yet. We still have the vehicle’s 12-volt electrical system to deal with.
In our final step, we must locate and then access the 12-volt battery. Once the battery is located, responders have two choices. We can disconnect the ground and positive cables from the battery or we can cut the cables (Step 7). If the decision is made to cut the battery cables, then we should “double cut” the cables. Taking a “chunk” out of each cable ensures that the fresh-cut ends will not touch each other and re-establish electrical continuity. Cutting cables should be done if disconnecting the cables is not a viable option. Disconnecting is the recommended action.
The issue responders face with an electric vehicle, as well as with a hybrid vehicle, is that it can continue to function with its 12-volt battery completely disconnected. This is due to the fact that a second source of 12-volt power comes from the high voltage battery through a DC-to-DC converter. This power keeps the electric vehicle completely functional even though the 12-volt battery has been completely taken out of the system.
During the research project with Mitsubishi i-MiEV vehicle, testing was conducted to demonstrate the importance of following these steps in this specific order. The i-MiEV electric vehicle was placed in “Park” with the vehicle’s ignition in the ON position. In other words, although sitting still and in “Park,” the vehicle was fully functional at this time. The electric vehicle’s green READY light was clearly visible within the instrument cluster.
To show that all electric functions were operational, the headlights were turned on and the four-way hazard flashers were activated. Instead of following the recommended Lock-Out/Tag-Out sequence, researchers left the ignition switch in the ON position and all electrical accessories operating. The 12-volt battery was then worked with, disconnecting the ground and positive cables from the battery itself.