Understand the unique service issues related to HEV high-voltage systems.
Correctly use appropriate personal protective equipment (PPE).
Explain hazards while driving, moving, and hoisting a hybrid electric vehicle.
OBJECTIVES: After studying Chapter 65, the reader should be able to:
ANSI • ASTM
CAT III • DMM • floating ground
HV • HV cables • IEC • Linesman’s gloves
NiMH • OSHA
HIGH-VOLTAGE SAFETY EQUIPMENT
Rubber Gloves Be sure high-voltage ( HV ) linesman ’ s gloves are available, rated at least 1,000 volts, class “0” by ANSI/ASTM.
Continued WARNING: HV cables and wiring are orange in color. High-voltage insulated safety gloves and a face shield must be worn when carrying out any diagnostics involving the high-voltage systems or components. The Occupational Safety and Health Administration ( OSHA ) requirements specify that HV gloves get inspected every six months by a qualified glove inspection laboratory. Use an outer leather glove to protect the HV rubber gloves. Inspect the gloves carefully before each use. High voltage and current (amperes) in combination is fatal. See Figures 65-1 & 65-2.
Figure 65–1 Rubber linesman’s gloves protect the wearer from a shock hazard. Figure 65–2 Wearing leather gloves over the linesman’s gloves helps protect the rubber gloves from damage. Continued NOTE: The high-voltage insulated safety gloves must be recertified every six months to remain within OSHA guidelines.
Before using the rubber gloves, they should be tested for leaks using the following procedure:
Figure 65–3 Checking rubber linesman’s gloves for pinhole leaks. Continued
Roll the glove up from the open end until the lower portion of the glove begins to balloon from the resulting air pressure. Be sure to “lean” into the sealed glove to raise the internal air pressure. If the glove leaks any air, discard the gloves.
The gloves should not be used if they show any signs of wear and tear.
CAT III–Rated Digital Multimeter Hybrid electric vehicles are equipped with electrical systems whose voltages can exceed 600 volts DC. A CAT III–certified digital multimeter ( DMM ) is required for making measurements on these high-voltage systems. Eye Protection Should be worn when testing for high voltage, considered by many to be anything over 60 volts. Most hybrid electric systems use voltages higher than this threshold. If the system has not been powered down or has not had the high-voltage system disabled, a shock hazard is always possible. Even when the high-voltage (HV) system has been disconnected, there is still high voltage in the HV battery box.
FIRST RESPONDER PROCEDURES
Identifying a Hybrid Vehicle To confirm whether a vehicle is a hybrid, look for the word “HYBRID” on the rear of the vehicle.
Figure 65–4 This Honda Accord hybrid is identified by the emblem on the rear deck lid. Figure 65–5 A hybrid electric vehicle can often be identified by looking for orange-colored cables under the hood, as well as other markings on the engine cover. Orange cables underhood or shielding bolted to the underside of the vehicle, indicates the vehicle is a hybrid.
Except for the Honda Insight and the Toyota Prius, there is very little difference in the exterior or interior appearance of hybrids, compared to those of their gasoline-powered counterparts.
Continued Power Source The main power source of all hybrids is a conventional internal combustion engine (ICE). During start-up and acceleration, an electric motor provides assistance to the engine. During braking and deceleration, the motor acts as a generator, recharging both high-voltage and the 12-volt battery. 12-Volt Battery A conventional flooded-type lead-acid 12-volt battery, powers all standard electronics. Most are nonspillable absorbed glass mat (AGM) designs. This battery also provides power to the high-voltage battery control systems. Disconnecting or cutting the negative cables to the battery may be necessary in some emergency situations.
Fuse Box Most hybrid electric vehicles have a fuse box in the engine compartment. Removing the main fuse from this box may be required in some emergency situations. High-Voltage Battery Module The electric motor is powered by a high-voltage battery module. Because the battery module is recharged by the electric motor whenever the vehicle decelerates or by the generator during cruise conditions, the battery never needs external charging. The high-voltage battery modules are often in plastic containers, and these cells are placed within a sturdy metal box. See Figure 65–6.
Figure 65–6 A Toyota Highlander hybrid battery pack with the cover removed.
Components in the battery box are completely insulated and isolated from the vehicle body.
Continued For safety, the high-voltage battery box is positioned behind seat backs or under the rear seat where it is well protected from potential damage in a collision. In the finished cells, electrolyte is nonliquid, nonflammable, nonexplosive, and creates no hazardous fumes or vapors in normal operating conditions and is sealed in a metal case. Small quantities of electrolyte, corrosive to human tissue, are used in NiMH battery cells.
High-Voltage Cables Electricity flows through either two or three heavy-duty orange cables. In some hybrid vehicles, high - voltage cables also deliver current to the air-conditioning (A/C) compressor. High-voltage cables are routed under the vehicle inside orange plastic protective shields. Where the cables lie close to the exhaust system, a metal thermal shield covers, the orange shield.
To reduce the risk of injury during the deactivation period, the following steps are recommended:
Keep out of the path of an undeployed front airbag, and do not cut into the center of the steering wheel or dashboard where the front airbags are stored.
Do not cut into the rear ( C ) pillar where the side curtain inflator is stored.
WARNING: Extreme heat (320–356°F [160–180°C]) can cause unintended airbag inflation. Follow recommended procedures to avoid possible injury from a deploying airbag or inflator. Airbags and Tensioners All hybrids have front airbags and seat belt tensioners. Most have side airbags for front-seat occupants; many with side curtain airbags. These systems use pyrotechnic devices with a deactivation time of up to three minutes.
ELECTRIC SHOCK POTENTIAL
Unprotected contact with electrically charged (“ hot ” or “ live ”) high-voltage components can cause serious injury or death.
Continued Receiving an electric shock from a hybrid vehicle is highly unlikely because of the following:
Contact with battery module or components in the battery box can occur only if the box is damaged and contents are exposed, or it is opened without proper precautions.
Contact with the electric motor can occur only after one or more components are removed.
High-voltage cables can be easily identified by distinctive orange color, and contact with them can be avoided.
The system main relays (SMRs) disconnect power from the cables the moment the ignition is turned off.
There are only three situations in which the cables can potentially be “ hot ” in most hybrid vehicles:
The ignition switch is on, the engine is running, and the vehicle is accelerating. In this case, the high-voltage battery module is sending current to the motor. (This is not likely to be a concern to first responders.)
The ignition switch is on, the engine is running, and the vehicle is decelerating. In this case, the motor is generating electric current and sending it to the high-voltage batteries.
The third situation in which the cables can be hot occurs when the ignition switch is on, the engine has been turned off by the auto idle stop feature, and the air conditioner is on. In this case, the high-voltage battery module is sending current to the air-conditioner compressor.
NOTE: The only condition common to all three situations in which the cables can be “hot” is that the ignition is on. Therefore, when the ignition switch is off, electric current cannot flow into the high-voltage cables because the system main relays that control the high voltage are turned off when the ignition is off. See the chart on Page 790 of your textbook.
Before attempting to rescue occupants or move a damaged hybrid vehicle, potential for current flow from the electric motor or battery module through high-voltage cables needs to be removed.
PREVENTING CURRENT FLOW THROUGH HIGH-VOLTAGE CABLES Continued Method One Turn the Ignition Switch Off This action turns off the engine and the electric motor, preventing current flow into the cables. It also turns off power to the airbags and the seat belt tensioners. Remove the key so the vehicle cannot be restarted. There are two recommended methods: NOTE: Turning the ignition key to the OFF position stops the flow of electricity in the cables.
Method Two Remove the Main Fuse Cut the negative 12-volt battery cable(s). This turns off the engine and the electric motor, preventing current flow from the motor into the cables.
Figure 65–7 The high-voltage disconnect (service) plug is located on the left side of the rear seat in a Toyota Highlander hybrid vehicle.
Locate the underhood fuse box, and remove the cover (see the owner’s manual for fuse box locations).
This also cuts power to the airbags and the seat belt tensioners, as well as to the high-voltage battery controllers, preventing current from flowing into the cables from the high-voltage battery. Continued
Locate the main fuse by referring to the diagram on top of, or inside, the fuse box cover. On a Honda Civic hybrid, use a Phillips screwdriver and unscrew the main fuse assembly and remove it from the box.
WARNING: Power remains in the high-voltage electrical system for up to 10 minutes after the HV battery pack is shut off. Never touch, cut, or open any orange high-voltage power cable or high-voltage component without confirming that the high voltage has been completely discharged. Continued
See the chart on Page 791 of your textbook. 3. Locate the 12-volt battery and cut the negative cables with diagonal cutters. See the 12-volt battery location chart below. NOTE: If neither method to stop the engine can be performed to prevent current flow into the high-voltage cables, use extreme care, do not cut into the cables, and do not touch damaged cables as they may be “hot.”
The vehicle computer determines the mode in which the vehicle operates to improve fuel economy and reduce emissions. The driver cannot manually select the mode.
Never assume the vehicle is shut off just because the engine is off. Always look for the READY indicator status. The vehicle is shut off when the READY indicator is off. The vehicle may be powered by: Silence is Not Golden 1 . The electric motor only 2 . The gasoline engine only 3 . A combination of both Figure 65–8 The Ford Escape Hybrid instrument panel showing the vehicle in Park and the tachometer on “EV” instead of 0 rpm. This means that the gasoline engine could start at any time depending on the state of charge of the high-voltage batteries and other factors.
SRS Airbags and Seat Belt Pretensioners Two electronic frontal impact sensors are mounted in the engine compartment. Front seat belt pretensioners are mounted near the base of the B -pillar. A frontal dual-stage driver airbag is mounted in the steering wheel.
Continued WARNING: The SRS computer is equipped with a backup source that powers the SRS airbags up to 90 seconds after disabling the vehicle. The front-seat side airbags and the curtain-shield side airbags may deploy independent of each other.
Both positive and negative high-voltage power cables are isolated from the metal chassis, so there is no possibility of shock by touching the metal chassis. This design is called a floating ground. High Voltage is Insulated from the Vehicle Body A ground fault monitor continuously monitors for high-voltage leakage to the metal chassis while the vehicle is running. If a malfunction is detected, the vehicle computer will illuminate the master warning light in the instrument cluster and the hybrid warning light in the LCD display. The HV battery pack relays will automatically open to stop electricity flow in a collision sufficient to activate the SRS airbags.
On arrival, emergency responders should follow their standard operating procedures for vehicle incidents.
Continued WARNING: Never assume a hybrid vehicle is shut off simply because it is silent. After disabling the vehicle, power is maintained for 90 seconds in the SRS system and 10 minutes in the high-voltage electrical system. Extrication 1. Immobilize the vehicle (chock wheels and set parking brake). 2. Disable the vehicle . 3. Stabilize the vehicle . Crib at four points directly under the front and rear pillars. Do not place cribbing under the high-voltage power cables, exhaust system, or fuel system.
Continued 4. Access the patients . Use normal glass removal procedures.Door removal/displacement. Doors can be removed by conventional rescue tools such as hand, electric, and hydraulic. 5. Door removal/displacement . Doors can be removed by conventional rescue tools such as hand, electric, and hydraulic. 6. Roof removal . The vehicle may contain optional curtain-shield airbags. If equipped and undeployed, it is not recommended to remove or displace the roof. CAUTION: Responders need to be cautious when working in close proximity to undeployed airbags and seat belt pretensioners. Deployed front dual-stage airbags automatically ignite both stages within a fraction of a second.
Continued 7. Dash displacement . The vehicle may contain optional curtain-shield airbags. When equipped, do not remove or displace the roof during a dash displacement to avoid cutting into the airbags or inflators. 8. Rescue lift airbags . Responders should not place cribbing or rescue lift airbags under the high-voltage power cables, exhaust system, or fuel system. 9. Fire . Approach and extinguish a fire using proper vehicle firefighting practices as recommended by NFPA, IFSTA, or the National Fire Academy (NFA). Water has been proven to be a suitable extinguishing agent. Perform a fast, aggressive fire attack. Attack teams may not be able to identify the vehicle as being a hybrid until the fire has been extinguished.
Spills Hybrid vehicles contain the same common automotive fluids used in other vehicles, with the exception of NiMH electrolyte (potassium hydroxide) used in the HV battery pack. The NiMH battery electrolyte is a caustic alkaline (pH 13.5) corrosive to human tissues. The electrolyte is absorbed in the cell plates and will not normally spill or leak out even if a battery module is cracked. A catastrophic crash that would breach both metal battery pack case and the plastic battery module would be a rare occurrence. Similar to using baking soda to neutralize a lead-acid battery electrolyte spill, a dilute boric acid solution or vinegar is used to neutralize a NiMH battery electrolyte spill.
Handle NiMH electrolyte spills using the following personal protective equipment (PPE):
Splash shield or safety goggles (Fold-down helmet shields are not acceptable for acid or electrolyte spills.)
Rubber, latex, or nitrile gloves
Apron suitable for alkaline materials
Neutralize NiMH electrolyte using a boric acid solution or vinegar; boric acid solution is 5.5 ounces boric acid to 1 gallon of water (800 grams boric acid to 20 liters water).
There are no unusual hazards if a hybrid electric vehicle is involved in a fire. It should be noted, however, that extremely high temperatures (320–356°F [160–180°C]) can cause undeployed airbags to deploy.
NOTE: If a fire occurs in the NiMH HV battery pack, the incident commander will have to decide whether to pursue an offensive or defensive attack. Continued
Offensive Fire Attack Flooding the HV battery pack, located in the cargo area, with large amounts of water at a safe distance will effectively control fire by cooling the adjacent NiMH battery modules below their ignition temperature. The remaining modules on fire, if not extinguished by the water, will burn themselves out.
Continued Defensive Fire Attack If the decision has been made to fight the fire using a defensive attack, the fire attack crew should pull back a safe distance and allow the NiMH battery modules to burn out. During this defensive operation, fire crews may utilize a water stream or fog pattern to protect exposures or to control smoke.
Pull the vehicle out of the water; use one of the procedures for preventing current from flowing through the high-voltage cables.
SUBMERGED OR PARTIALLY-SUBMERGED VEHICLE NOTE: There is no risk of electric shock from touching the body or the framework whether in or out of the water. Submersion Handle a hybrid vehicle fully or partially submerged in water by disabling HV battery pack, SRS airbags, and fuel pump.
Remove vehicle from the water.
Drain water from the vehicle if possible.
No. The computer of all hybrid electric vehicles monitors the connection between the high-voltage circuits and the body or frame of the vehicle. If water or an accident were to cause an electrical connection between high voltage and the body of the vehicle, high voltage is immediately turned off. Will I Get Shocked If I Drive My Hybrid Into Deep Water?
COLLISION AND REPAIR INDUSTRY ISSUES
Jump-Starting The 12-volt auxiliary battery may be jump-started if the vehicle does not start. The 12-volt auxiliary battery is often located under the hood but can also be located in the cargo area of some HEVs.
Continued Using a jump box or jumper cable from another vehicle, make the connections to the positive and negative battery terminals. Figure 65–9 Jump-starting a 2001–2003 Toyota Prius using a 12-volt supply to boost the 12-volt auxiliary battery in the trunk.
On the 2004+ Toyota Prius vehicles, there is a stud located under the hood that can be used to jump-start the auxiliary battery, which is located in the truck. The trunk has an electric latch and cannot be opened if the auxiliary battery is dead.
Figure 65–10 The underhood 12-volt jump-start terminal on this 2004+ Toyota Prius has a red plastic cover with a “+” sign. The positive booster cable clamp will attach directly to the vertical metal bracket. NOTE: The high-voltage HV battery pack cannot be jump started on most HEVs. One exception is the Ford Escape/Mercury Mariner hybrids, which use a special “jump-start” button located behind the left kick panel. When this button is pushed, the auxiliary battery is used to boost the HV battery through a DC-DC converter.
MOVING AND TOWING A HYBRID
If a disabled vehicle needs to be moved a short distance (to the side of the road) and the vehicle can still roll on the ground, the easiest way is to shift the transmission into neutral and manually push the vehicle. To transport a vehicle from an emergency location, a flatbed truck should be used if the vehicle might be repaired. If not available, the vehicle should be towed by wheel-lift equipment with front wheels off the ground (FWD hybrid electric vehicles only). Do not use sling-type towing equipment. In the case of 4WD HEVs such as the Toyota Highlander, only a flatbed vehicle should be used.
Moving the Hybrid Vehicle in the Shop After an HEV has been serviced, it may be necessary to push the vehicle to another part of the shop or outside as parts are ordered. Make sure to tape any orange cable ends. Permanent magnets are used in all the drive motors and generators and it is possible that a high-voltage arc could occur as wheels turn and produce voltage. Another way to prevent this is to use wheel dollies.
Figure 65–11 Use of a warning cover over the steering wheel helps others realize that work is being performed on the high-voltage system and that no one is to attempt to start or move the vehicle.
A sign that says “HIGH VOLTAGE—DO NOT TOUCH” could also be added to the roof of the vehicle. Keep the keys out of the vehicle and safely stored.
Figure 65–12 A lock box is a safe location to keep the ignition keys of a hybrid electric vehicle while it is being serviced. Notice that this lock box has two separate locks so it would require two people to open, helping to insure that no harm is done by accidentally attempting to start a HEV. Continued
Removing the High-Voltage Batteries The HV battery box should always be removed as an assembly, placed on a rubber-covered work bench, and handled carefully. All parts, especially capacitors, should be checked for voltage while wearing HV rubber gloves.
Figure 65–13 Insulated tools, such as this socket set, would provide an additional margin of safety to the service technician when working around high-voltage components and systems. Continued Always check for voltage as the components become accessible before proceeding. When removing high-voltage components, it is wise to use insulated tools.
Storing the High-Voltage Batteries If a hybrid is to be stored for any length of time, the state of charge of the HV batteries must be maintained. If possible, start the vehicle every month and run it for at least 30 minutes to help recharge the HV batteries. This is necessary because NiMH batteries suffer from self-discharge over time. High-voltage battery chargers are either not available or are hard to find even at a dealer. If the HV battery SOC was over 60% when it was put into storage, the batteries may be stored for about a month without a problem. If the SOC is less than 60%, a problem with a discharged HV battery may result.
Hoisting a Hybrid Vehicle When hoisting or using a floor jack, pay attention to the lift points. Orange cables run under the vehicle just inside the frame rails on most hybrids.
Figure 65–14 The high-voltage wiring on this Honda hybrid is colored orange for easy identification. Continued
Some Honda hybrid vehicles use an aluminum pipe painted orange that includes three HV cables for the starter/generator and also three more cables for the HV air-conditioning compressor. If damage occurs to any high-voltage cables, the MIL will light up and a no-start will result if the PCM senses a fault. The cables are not repairable and are expensive. The cables can be identified by an orange outer casing, but in some cases, the orange casing is not exposed until a black plastic underbelly shield is removed first.
Paint Ovens Nickel metal hydride (NiMH) batteries may be damaged if exposed to high temperatures, such as in a paint oven. The warning labels on hybrid vehicles specify that the battery temperature should not exceed 146°F (63°C). HV Battery Disposal The hybrid electric vehicle manufacturers are set up to ship NiMH battery packs to a recycling center. There is an 800 number located under the hood or on the HV battery pack that can be used to gain information on how to recycle these batteries.
NiMH batteries do not store well for long lengths of time. After a repair job, or when the HV system has been powered down by a technician and powered up again, do not be surprised if a warning light(s), codes, and the MIL are illuminated. If everything was done correctly, a couple road tests may be all that is required to reset the MIL. The HV battery indicator on the dash may also read zero charge level. After a road test, the HV battery level indicator will most likely display the proper voltage level. High Voltage Battery SOC Considerations
Whenever a hybrid electric vehicle is in an accident or has been submerged in deep water, the insulation should be tested before the high-voltage circuits are activated. An insulation tester, often called a megaohmmeter, such as the Fluke 1587, is used. One meter lead is connected to one of the high-voltage cables and the other lead is connected to a good, clean body ground. There should not be any continuity.
The tester applies a test voltage on the meter leads.
The tester then measures the voltage and the current.
the tester then calculates the resistance and displays the reading.
PHOTO SEQUENCE HV Glove Use
PHOTO SEQUENCE HV Glove Use
( cont. )
Personal protective equipment (PPE) for work on hybrid electric vehicle includes the wearing of high-voltage rubber gloves rated at 1,000 volts or more worn with leather protective gloves to help protect the rubber gloves.
A digital meter and meter leads that meets CAT III standards should be used when working around the high-voltage section of a hybrid electric vehicle.
Safety glasses and a face shield should be worn whenever working around the high-voltage circuits of a hybrid electric vehicle.
The high-voltage system can be shut off by disconnecting the high-voltage circuits and being sure the ignition is off.
Disconnecting the 12-volt battery is additional security that the high-voltage circuits are depowered.
For most situations, first responder actions should be the same as if the vehicle were conventional.
When servicing a hybrid electric vehicle, always observe recommended safety procedures.