Article and photos by Jason Emery
The HS250h is the fourth hybrid model that Lexus offers and is its most efficient hybrid (figure 1). This is also the first compact hybrid luxury sedan. This model was just released as a hybrid and uses many of the same components as the third-generation Toyota Prius.
Since this model does not have any truly distinguishing design features identifying it as a hybrid, responders must look for external markings. These markings, or badging, can be found on both rear doors (figure 2) and on the right side of the trunk (figure 3). Responders can also look at the rear "deck" area behind the rear seat for the battery cooling vent (figure 4).
Looking at the dashboard, you will find that in place of the traditional tachometer, there is a gauge that indicates power output. The vehicle's "ready" light is to the right and above the power meter (figure 5). When the ready light is lit, it indicates that although the vehicle's engine may not be running, the vehicle is ready to move on its electrical motors alone.
The engine compartment contains several visual clues that a vehicle is a hybrid. Orange wiring is visible, as is the "Lexus Hybrid Drive" logo on the engine cowling (figure 6). This model also includes a sticker on the underside of the hood that indicates the location of the high-voltage and the 12v-batteries.
Hybrid Systems and Operation
The HS250h uses a 244.8v high-voltage battery for its electrical power storage. This battery module consists of 34 low-voltage (7.2v) Nickel Metal Hydride (NiMH) dry-cell batteries connected in a series. Since they are "dry-cell" batteries, they do not constitute a significant leak hazard, even if crushed. The battery pack is enclosed in a plastic case and is in the area behind the rear seat. Consistent with other hybrids, this battery is recharged using a process known as "regenerative breaking" as well as power from the engine. The HS250h is a "full" hybrid and can move at lower speeds (typically 20 mph or less) on battery power alone. At higher speeds and during acceleration, the electric motors and gasoline engine can work in tandem. This model uses both DC and AC electrical currents in its hybrid system. The 245v DC supplied by the battery is stepped up to 650v AC for use by the electric motors. This is done through an inverter/converter system located near the electric motor.
When approaching a vehicle involved in an accident, be sure to do so in a manner that does not place you in the direct line of travel (front or rear). This holds especially true for hybrids--it may sound as if the vehicle is immobile because there is no engine noise, but in reality it is in its "ready" mode. Should the driver accidentally take his foot off the brake or hit the accelerator, the vehicle can move without warning. To secure the vehicle from potential movement, be sure to engage the parking brake and place it into "park" if possible. Wheel chocks can also be deployed to secure the vehicle if you are unable to use the methods above. In the case of the HS250h, the gear shift selector does not have a "park" selection. Below the gear selector is a "park" button to set it in park. The vehicle also automatically goes into park when the power button is used to shut it off.
Disengaging the high-voltage and occupant protection systems should be the next step in making the vehicle safe for response personnel. The fastest method for doing this is to shut off the vehicle's ignition using the button on the dash (figure 7) and disconnecting the negative cable from the 12v-battery located in the right side of the trunk, behind a panel (figure 8). The other option, if you cannot access the passenger compartment, is to locate the fuse box on the right-hand side of the engine compartment and remove the IGCT No. 2 fuse (red colored 10 amp) (figure 9). If you are unsure of which fuse is the appropriate one, pull them all. Once the fuse is removed, disconnect the 12v battery in the trunk as well.
This model is equipped with a remote smart key system similar to the one found in the Prius. In addition to smart key fob, the owner also has the option of getting a card smart key (credit card size) that can be stored in a wallet. Both options have a hidden metal cut key that can be pulled out and used in the locks (figure 10). This smart key system allows the user to access the vehicle and start it up without using the traditional "key-intheignition" method. Once the vehicle detects the key in proximity, the driver can start the vehicle by pushing the ignition button. To prevent the vehicle from being started with the push of the button, remove the smart key at least 16 feet from the vehicle. If you cannot locate the key, be sure to disconnect the 12v-battery in conjunction with shutting off the vehicle using the power button.
After the power has been removed from the occupant-protection systems, anticipate that the air bags and other safety systems will be deactivated in approximately 90 seconds. This model is equipped with 10 air bags and active front headrests.
As with all hybrids, there are no specific techniques for extrications involving the HS250h. Responders must take care not to cut through the high-voltage cables or components. In the HS250h, the high-voltage cables run underneath the vehicle roughly in the center of the passenger's side, in an area not typically considered a cut point. The orange high-voltage cables are not visible on the underside of the vehicle; he area is covered with a black plastic. (figure 11) Responders should be aware of the large number of air bags (10) found in this model and identify their locations. Seat-belt pretensioners are also located in the base of the B post and near the C post for the rear seats. Finally, be aware that the inflators for the side curtain air bags are in the roof rails, in the area above the B posts.
The basic guidelines for the Lexus HS250h closely mirror those for many of the other full hybrid models currently on the road. Prior to extrication operations, responders should always be on the lookout for indicators of a hybrid or other types of alternative-fueled vehicles. When conducting extrication operations, be aware of the large number of air bags found in this model. Also be sure to address the smart or proximity key when securing the vehicle.
If you have been involved with an incident involving hybrid or alternative fuel vehicles please contact Jason@etsrescue.com. Case studies involving specific incidents will help further educate firefighters on the proper methodology for dealing with hybrids and other alternative fueled vehicles.
Jason Emery has been with the Waterbury (CT) Fire Department for 15 years and is a lieutenant with its rescue/hazmat company. He is a 19-year veteran of the fire service, a certified fire instructor, and holds a bachelor's degree in fire science from the University of New Haven. He has taught extensively on the subject of hybrid vehicles and is a FDIC lecturer. He is the founder of Emergency Training Solutions, LLC and is the lead PowerPoint designer for the soon to be released Fire Engineering Handbook for Firefighter I & II. He can be reached at email@example.com.
Subjects: Hybrid vehicle hazards and extrication