by Jeff Poole
An increasing number of hybrid vehicles entering the bays of automotive and collision repair facilities means that you need the proper training to ensure accurate repairs and keep yourself safe.
The first commercially successful hybrid was the Toyota Prius, introduced first in Japan (1997) and then in the U.S. (2001). Hybrid vehicles, now available from most manufacturers, are common on the roads and are showing up in collision repair facilities.
Electric vs. Hybrid
Whereas an electric vehicle (Nissan’s LEAF) sends power to the wheels directly from electric motors, a hybrid electric vehicle (HEV) sends power to the wheels from electric motors, a gas motor or some combination of the two. One is propelled only by electricity; the other includes a gas-powered engine for assistance in moving the vehicle.
An electric vehicle may have a gas engine also, but its purpose is to function as a generator. This is referred to as an extended-range electric vehicle (E-REV) because it can generate its own electricity on board. As long as there’s fuel in the tank, the batteries can be recharged and electricity can propel the vehicle farther than batteries alone.
The 2011 Chevrolet Volt is an extended-range electric vehicle. It drives without gas or emissions for about 40 miles with a full charge and normal operating conditions. When the batteries are about 70% depleted, the gas engine starts and extends the range by providing energy for the drive motor, and excess energy is used to charge the batteries.
When convenient, an electricity source can be plugged into the vehicle to charge the batteries. The 16-KWH lithium-ion battery pack is backed by a 100,000-mile, eight-year warranty. EPA ratings are slightly different for this E-REV, showing 93 miles per gallon (mpg) running on electricity only, 37 mpg with the engine running and a combined 60 mpg using both under normal conditions.
A full hybrid vehicle is capable of complete electric propulsion under certain conditions. When needed, the internal combustion engine starts up and provides assistance. A mild hybrid is propelled by the internal combustion engine with assistance from the electric motor. Some hybrids can be recharged with a plug-in electrical source.
The Toyota Prius is a full hybrid. It can operate solely on battery power at lower speeds, depending on power demand and battery charge level. The 2011 Prius has an EPA rating of 51 mpg in the city (due to start-stop systems) and 48 mpg for highway driving (due to more gasoline being used).
Honda hybrids are all mild hybrids. The gas engine may get assistance from electric motor power under the right conditions. The ’11 Honda Civic Hybrid has an EPA rating of 40 mpg city/43 mpg highway.
These various designs have several things in common. Each has:
An engine stop/start system to conserve fuel when stopped or under other conditions;
A regenerative braking system, changing kinetic energy back into electricity;
Technology to monitor and control all the different systems on-board; and
A 12-volt system that controls the high voltage system.
Each also requires specific information, procedures and training to properly and safely repair them.
A typical D-size flashlight battery provides 1.5 volts, and putting your fingers across the terminals barely causes a sensation. However, put several of them together and you can receive a noticeable jolt. Add enough of them and they can produce a lethal shock.
A Ford Escape battery pack contains nickel-metal hydride battery cells (NiMH) containing 1.2 volts each. With 250 NiMH cells connected in series, the total charge would be 300 volts (250 x 1.2). This level of voltage is needed to move the vehicle, but can also be dangerous or lethal to human beings.
How much current does it take to cause an electric shock? When your body completes a circuit and becomes a conductor, electricity is flowing through your body. With each index finger on a typical D-size flashlight battery terminal, electricity is flowing through your body, but not very much.
Higher electrical pressure (voltage) can provide an increased flow of current (amperes) through your body, depending on resistance (ohms).
According to Ohm’s law, lower resistance causes higher electrical flow. With a high-voltage source such as a hybrid vehicle battery and a low-resistance circuit such as your uninsulated body, amperage could easily be high enough to kill you.
NiMH batteries are the current leader in production hybrids, but with a greater energy storage capacity per pound, lithium-ion batteries are “making a charge.” With either battery composition, safety is your No. 1 consideration.
High-voltage batteries typically contain a warning that states, “You will be killed or hurt.” Notice the emphasis on the word “killed.”
Remove all jewelry when working around electrical components. These metal pieces are excellent conductors, and lower resistance means increased current. You don’t want your rings or wristwatch melted, especially while you’re wearing them.
Wear the right gloves for the voltage. Lineman’s Class “0” gloves are rated to protect you up to 1,000 volts. Leather gloves over lineman’s gloves will help protect them from punctures or tears. Electricity will find even the smallest pinhole, and with that voltage, current can be deadly.
Your gloves should be inspected before each use with an air test (inflated). If air can’t get out, electricity can’t get in. OSHA regulation 29 CFR 1910.137 requires that all insulating gloves must be electrically tested before first issue and re-tested every six months thereafter.
A quality digital volt-ohm meter is essential to determine that voltage isn’t present before touching a wire or component. You don’t want to discover dangerous voltage the hard way.
Quality electrical tape is useful for temporarily wrapping exposed wires and connectors to avoid unintentional connections or current flow.
In case of fire, keep a proper fire extinguisher nearby. Make sure it’s a class C, ABC or CO2 that will put out an electrical fire.
In the unlikely event that the battery pack is damaged and leaking electrolyte, wear appropriate protective clothing and equipment to avoid coming in direct contact with it. The electrolyte in NiMH batteries is highly alkaline and can be neutralized with a boric acid solution.
Both electric and hybrid vehicles have safety disconnects that provide an additional level of safety for repairers. Minor body repair operations may not require their use, but more involved work requires more personal protection, including a high-voltage system disconnection.
Typically, the sequence is: turn the ignition off, disconnect the 12-volt battery and then remove the high-voltage service disconnect. Of course, each automaker does this a little differently, so check the specific OEM procedures to observe proper waiting periods and to avoid setting trouble codes by a wrong sequence.
Even with the vehicle shut down and disconnected, dangerous high voltage is still contained in the battery pack. It may also exist in other components of the high-voltage system, including capacitors or other devices. These have the capacity to kill you. They may take 5 to 10 minutes to discharge before operations can be performed safely.
Don’t forget your gloves. Use a DVOM to make sure that a wire or component is safe before removing your lineman’s gloves to work on it. A “touch test” here could be deadly.
Some vehicles use a “smart key” that can activate vehicle systems just by being in proximity of the vehicle. Be sure it’s an appropriate distance away from the vehicle or, better yet, deactivate this feature. This may be done with a deactivation switch or by disconnecting the 12-volt battery.
Know your wire colors!
Red and black are typically power and ground for 12-volt systems. Blue wires on Saturn and Malibu hybrids are for the 36-volt starter/generator system. Yellow wires for electric power steering systems may be 27 to 42 volts. Orange cables carry power for the high-voltage system.
High voltage cables may be damaged in a collision event. There are no repair procedures for these. Replace damaged cables.
Electric power steering is becoming more common on not only electric and hybrid vehicles, but also conventional vehicles. Voltage for these systems can also be dangerous. There are specific procedures to determine proper operation an important part of damage analysis as well as post-repair quality inspections.
When reassembling the vehicle, be sure to properly torque all connections and reinstall all safety assurance interlocks.
A few hybrid vehicles have conventional air conditioning compressors, and traditional service procedures apply. Electric air conditioning compressors can also be found on electric and hybrid vehicles. They may also have a belt drive.
High-voltage electric compressors require a unique insulating refrigerant oil that’s specific to the challenges of an electric compressor. Most systems don’t allow for a leak-checking dye. Understand the manufacturer-specific service procedure to avoid contamination of the system, which could be a costly mistake.
From 2004 to 2009, the Toyota Prius had a coolant storage reservoir mounted outside the left front lower frame rail. This is a double wall canister designed to store hot coolant to help the gas engine warm up under certain conditions. In that position, it’s vulnerable to collision damage and is frequently replaced. There are specific procedures needed to properly bleed the system after replacement.
Many hybrids have two separate cooling systems. They may require two different bleeding procedures for proper operation of both.
As part of their drive systems, many of these vehicles have motor generators connected to the drive wheels capable of generating electricity during deceleration and braking.
Motion of the wheels creates an electric current which can be captured to recharge the batteries. That also means that an electric current is generated when the vehicle is pushed or rolled in the shop.
To avoid a potential hazard, use wheel dollies to safely move the vehicle.
As the number of hybrid electric vehicles increase, you can be assured of seeing more of these vehicles damaged and in your shop’s bay for repairs. Remember stay educated on the technology, and think safety first.
Jeff Poole is an I-CAR trainer who has been part of the collision repair industry since 1989. Prior to 1989, he gained valuable exposure to the industry through his father, now a retired vocational instructor from Silver Spring, MD. Poole joined the I-CAR team in 1995 and is currently working in the role of performance training coordinator, providing training and support to instructors throughout the U.S.