Extrication Tips: Hybrid vehicles
With soaring gas prices and the demand for more environmentally friendly vehicles, it’s no wonder the hybrid is gaining in popularity. For emergency responders, hybrid vehicles are no more dangerous than conventional vehicles if handled in the correct manner, despite the rumours you may have heard through uneducated media hype.
By Randy Schmitz
First off we will touch base on the different types of modern hybrids today by discussing, their basic design and function. We will then go into the step-by-step emergency response procedures.
When a vehicle uses combined propulsion systems to provide motive power, it is called a hybrid vehicle. There are many types of combined propulsion systems but the most commonly used is gasoline-electric, also known as a gasoline-electric hybrid. Electric hybrid vehicles use gasoline to power internal-combustion engines (ICE), and electric batteries to power electric motors.
Modern hybrid cars are driven by electric motors powered by both batteries and an ICE. They recharge their batteries by capturing kinetic energy called regenerative braking. As well, when cruising or idling, some of the output of the combustion engine is fed to a generator which produces electricity to charge the batteries. Nearly all hybrids still require gasoline/diesel as their main fuel source.
There are many types of hybrids, differentiated by how the electric and fuelled halves of the powertrain connect and at what times each portion is in operation. The two major categories are series hybrids and parallel hybrids.
With a series hybrid, only the electrical motor keeps the vehicle in motion. The gas-burning engine actually drives an alternator that will create the electricity that flows to the electric motor or to the high voltage (HV) battery for future use. When the car is running on batteries alone and starts to lose power, the gas-burning engine kicks in and recharges the HV batteries to a specified level so that the vehicle may once again run on its battery power. The Honda Insight is a series hybrid.
Parallel systems connect both the electrical and internal combustion systems to the mechanical transmission. These are the most common types of hybrids at present. They can be further sub-categorized depending upon how balanced the different portions are at providing motive power, i.e., a vehicle that can run on just the engine, just the batteries or a combination of both. The Prius and the Escape models are examples of this.
An assist or mild hybrid uses the engine for primary power with a torque-boosting electric motor connected to a largely conventional powertrain. This is essentially a conventional vehicle with an oversized starter motor, which allows the engine to be turned off whenever the car is coasting, braking or stopped. Yet it can restart quickly and cleanly. A plug-in hybrid electric vehicle (PHEV) is a full hybrid, able to run in electric-only mode, with larger batteries and the ability to recharge from the electric power grid. They are also called fuel-optional, or “griddable” hybrids. A hydraulic hybrid vehicle uses hydraulic and mechanical components instead of electrical ones.
Stored battery power
Aside from their 12-volt conventional lead acid battery that runs accessory power systems in the vehicle, most hybrids use high voltage Nickel Metal Hydride (NiMH) batteries for their light weight and internal design. These NiMH batteries can be discharged and recharged over and over again.
Most of these HV battery packs are made up of a series of smaller batteries that are connected together and can add up to a higher voltage, therefore these batteries can carry a large amount of energy! And a lethal amount of voltage. These battery packs can range in power from an intermediate level of 36 to 42, up to a high level of 60 to 650 volts. Some examples are 36 volts for the 2007 Saturn Vue; 42 volts for the GMC Sierra/Chevy Silverado truck; 144 volts for the Honda Insight; 330 volts for the Ford Escape Hybrid, and up to 650 volts for the Toyota Camry. This is more than enough juice to electrocute anyone that accidentally comes in contact with the HV battery, cables or other connecting high voltage components.
Car manufacturers generally try to protect the HV battery from becoming breached by a collision by putting them near, under or behind rear seat areas, enclosed in tough metal boxes.
The HV battery packs are designed to have relays that automatically open and disconnect the HV battery if a collision is severe enough to deploy the airbags or trip the crash sensor. The high voltage is also shut down as soon as the ignition is turned off or the 12-volt battery is disconnected.
Warning! The high voltage system may remain powered for up to 10 minutes after the vehicle is shut off or the 12-volt battery is disconnected or the safety disconnect switch is removed. This is because hybrid vehicles use a series of capacitators to store and release energy as needed. To prevent serious injury or death from severe burns or electric shock, avoid touching, cutting or breaching any orange high voltage power cable or high voltage component.
High voltage cables
From the HV battery pack situated near the rear of the vehicle are the orange colour-coded cables that carry the stored energy to the electric motor in the front engine compartment. The orange colour for the cables has by fluke become an industry standard for high voltage hybrid cables. The one exception is blue cable introduced by General Motors on its 2007 Saturn Vue and 2004 GM Silverado/Sierra truck hybrid models. This blue cable is classified in their emergency response guides as “intermediate voltage” cable 30-60 volts. The hybrid GM and Chevy trucks also use orange cable for their high voltage wiring harness which has 120 volts running through it.
HV cables run underneath the vehicle generally in the middle of the vehicle or near the driver’s seat area in tough plastic sheaths that protect the cables from damage. Rescuers should take caution as these cables are not always obvious because the plastic sheath may be white or black in colour which can make it difficult to see.
If the HV cables that are placed underneath the vehicle were to be stripped of their insulation – from running over something like an extruded maintenance-hole cover, the control module would sense this interruption, trip the system and shut it down. This happens because all the HV wires are individually wrapped with a ground wire.
High voltage disconnect switches are usually located near or on the steel protective covers of HV battery packs.
Depending on the make and model of hybrid, access to these switches may entail removing metal covers, rear seats, plastic trim, etc., to flip the switch to the off position. When turned, flipped or switched to their off position, all high voltage electrical flow to and from the battery is shut off and isolated within the battery itself.
Also built into the system are ground fault monitors (GFM) that will sense any circuit problems, shorting of wires or water submersion and shut down the flow of high voltage. Many hybrids also have inertia switches, crash or impact sensors that will interrupt the flow of power in the event of a collision and SRS deployment.
Note: To date no one has been injured or electrocuted by a hybrid electric vehicle. An extensive search of news articles by the author failed to turn up any reports of service technicians, emergency responders or motorists being zapped by a high voltage hybrid.
Be aware of hazards
Responders still need to be aware of the hazards of high voltage and treat this with respect. Rescue workers could, for instance, cut through an HV cable with their tools while attempting to extricate a patient from an accident situation involving a hybrid vehicle, and harm themselves or patients if the proper procedures are not followed prior to coming in contact with the vehicle.
The hybrid vehicles have been designed with many features for your protection. These features should help provide you with safe access to the vehicle under various emergency conditions. Furthermore, whenever you approach a high voltage vehicle, be it in a fire, rescue or recovery situation, you have to follow this golden rule: “Always assume the vehicle is powered up!”
Emergency response procedures
Personnel arriving at the scene of a fire or crash-related incident involving a gasoline-electric hybrid vehicle should complete the seven-step hybrid vehicle “Lock-Out Tag-Out” protocol as soon as practical after arrival and completion of initial scene assessment.
1. Identify the vehicle as a hybrid.
2. Immobilize, then stabilize, the vehicle.
3. Access passenger compartment.
4. Shift gear selector/park brake lever.
5. Turn ignition off.
6. Check that the dash indicator lights go out.
7. Disconnect/shut down 12-volt battery.
1. Identify the vehicle as a hybrid. This may not always be easy as most hybrids look nearly identical to their conventional non-hybrid models. With some hybrids the only external visible indication is a badge on the rear or the side of the vehicle; depending on the type of crash the badge may have been destroyed or cannot be seen. The interior will have some distinct features to help you identify it as a hybrid: the dashboard area will have hybrid switches or buttons with “hybrid” written on them, “battery energy level gauges” may be written on the instrument panel, and perhaps wording such as “READY” or “AUTO-STOP” may be visible in the instrument panel.
A thorough inner circle survey should be able to confirm a hybrid vehicle, if not initially apparent. Because you may not be able to identify all hybrids, these procedures should ensure the safety of emergency personnel and vehicle occupants in every situation.
2. Immobilize, then stabilize, the vehicle. Chock the wheels front and back even if the vehicle is on its side. Some hybrids are all-wheel drive and it is possible for the vehicle to move if only one wheel is chocked.
An important fact that emergency responders need to understand is that due to the nature of hybrids, they may appear to be turned off when in fact they are in “sleep” mode. Similar to the way a golf cart sheds its power when it comes to a stop and lays dormant, the hybrid may power back up and take off without hesitation should the driver press the accelerator pedal.
If we apply this same example to an accident scene, first responders could be placing themselves at risk by conducting initial surveys in front of or behind a sleeping hybrid vehicle. Should the driver accidentally step on the accelerator, the vehicle could silently lurch forward and run over emergency personnel.
For an upright vehicle, crib at four points directly under the front and rear pillars; be careful not to place cribbing under high voltage cables. If the vehicle is not on all four wheels, follow your department’s side or roof resting stabilization procedures, making sure you do not come in contact with the HV cables on the underside of the vehicle.
3. Access passenger compartment. Traditional methods of gaining access should be followed. Scan the vehicle interior for airbags, try to open doors (try before you pry). If they are inoperable, gain access by removing the tempered glass. You must be able to reach the gear shift selector and/or the ignition key.
4. Shift gear selector/park brake lever. Once you have access to the inside of the vehicle, move the gear shift to the park position (there could also be a button to depress near the dash with the word “OFF” printed on it), or if it is a manual transmission, move the shift lever to the neutral position. This will ensure that the vehicle cannot move accidentally. Pull the park brake lever or, if possible, depress the emergency brake pedal.
5. Turn ignition off. Some hybrids use a conventional type ignition key that can be removed as soon as the transmission is placed in park. Others have a “smart key” which utilizes a wireless transceiver that communicates with the vehicle, provided it is in close proximity. This feature allows the smart key to lock and unlock the doors, trunk and also start the vehicle without inserting it into the ignition switch. The proximity range of the key to the vehicle is anywhere within 16 feet (five metres). As long as the key is within the proximity range, the vehicle can be driven, therefore this key could also be found in the driver’s pocket.
If the smart key is not in its docking slot, there is usually a switch under the steering column that can be turned off to deactivate the smart key system. When this switch is turned off, all lights will go out on the dash. If the power is still on, the high voltage system is still active.
Turning off the ignition will accomplish many functions. It will shut down hybrid systems, open relays to the HV battery pack isolating it from the rest of the vehicle’s HV cables and components, shut off the fuel pump to the engine and eliminate low voltage power to the SRS control module.
6. Check that the dash indicator lights go out. If the vehicle is shut off, the instrument cluster gauges will be “blacked out” or not illuminated. At this time, turn on the emergency flashers as this will indicate to everyone in the area that there is still power to the vehicle.
7. Disconnect/shut down 12-volt battery. Locate the 12-volt battery; it may be under the hood or in the trunk. If your department’s policy is to disconnect the cables, find the negative cable terminal and unbolt the ground cable, then do the same for the positive cable. This will help ensure that there is no sparking. Tape off the ends of the cables with electrical tape so power cannot be re-introduced to the system.
If your department’s policy is to cut cables, double cut negative first, then double cut the positive cable, taking out at least a two-inch section of cable to make sure the two ends cannot make contact and re-introduce power to the system. When all the power is disabled on the vehicle, the emergency flashers will go out.
Note: As mentioned previously, hybrid HV battery packs utilize “high voltage service disconnect switches” at or near the HV battery pack. When they are switched off or removed they will cut all power to and from the system, and isolate and contain it to the battery pack. Only as a last resort and after all above options have been tried and have failed, should you attempt to remove or turn off the service disconnect switch. These are to be used for service technicians to repair or to do service work on the vehicle.
Extrication can now begin by following your department’s standard protocols for patient removal.
Following these few simple rules as noted above for hybrids should be enough to help first responders save lives and remain safe in the process.
Hybrid vehicle fires
Firefighters will not be shocked or electrocuted fighting a hybrid vehicle fire even if there is direct flame impingement on the battery pack itself. Putting out fires in hybrids does not generally differ from regular car fires. While attacking a hybrid vehicle fire, it is important to use copious amounts of water to cool the metal box that houses the HV battery pack and the internal plastic cell modules. Do not remove the metal cover of the high voltage battery pack. If the internal cells are actually on fire, testing has shown that they will burn themselves out.
According to Material Safety Data Sheets regarding NiMH batteries on fire, they will produce toxic fumes from materials such as nickel, cobalt, cerium, etc. (see MSDS sheets by Panasonic NI-MH batteries for more details). They also may produce hydrogen gas. As with all car fires, SCBA must be worn while extinguishing the fire.
For more detailed information involving hybrid vehicle emergency situations, contact your local Toyota, Honda, Ford and GM dealers. They will be more than happy to provide you with information about their hybrid vehicles. All vehicle manufacturers offer an “Emergency Response Guide” at no charge, to help you safely deal with their specific make and model of hybrid.
The above information and procedures are only guidelines and are intended to be generic in nature. I encourage you to seek all the information outlined in the emergency response guides available and develop your own department protocols. The information contained in this article, however, should give you a good starting point.
Randy Schmitz is a Firefighter/Vehicle Extrication Instructor with the Calgary Fire Dept. and has been involved in the extrication field for 13 years, competing at all levels, including world challenges. He is the Alberta chair for TERC Canada, a regional judge for TERC events and teaches extrication courses across North America. Contact him at email@example.com