Tackling hybrid electric vehicle repair

Jan. 1, 2020
EV and HEV repair can be a very dangerous, even life-threating workplace environment if proper precautions are not taken.

Though hybrid vehicles have been around for some years, each year new variations are introduced. In some hybrid electric vehicles, a small gas engine produces the electricity, which drives the vehicle. In others, an electric motor assists the gas engine, which propels the vehicle. There are plug-in hybrids; they can be plugged in at home or at public charging stations (though there are not very many of these yet) to charge the high voltage battery, thus giving the vehicle a longer range and much better gas mileage. (Some claim over 100 miles per gallon.) There are pickups and trucks with electric-assisted transmissions, and also full electric vehicles (without any gas engines to charge the batteries), and even high performing, high speed full electric sports cars.

In short, there is a staggering array of electric vehicles (EV) and hybrid electric vehicles (HEV) that collision repair technicians will encounter. The good news is that the skills needed to repair the bodies and frames of such vehicles are not much different than those needed to repair any other vehicles, though new types of equipment must be checked. The bad news is that EV and HEV repair can be a very dangerous, even life-threating workplace environment if proper precautions are not taken. High voltage batteries (300 volt or more, depending on the vehicle) can kill a technician who has not disarmed the high voltage system properly. Regenerative breaking systems, even with the battery disconnected, can produce enough electricity to injure a tech, just by his or her pushing the disabled vehicle around the shop. Heat from the booth can damage or reduce the life expectancy of a high voltage battery if the manufacturer recommendations are not followed. Even the equipment that keeps us safe as we disarm a high voltage (HV) battery must be tested and handled properly, or it may fail.

High voltage PPE
As technicians, we are familiar with personal protective equipment (PPE), such as glasses, gloves and respirators; but with HEVs and EVs, the PPE gloves take on a new dimension of importance. First needed, and possibly most important, is a set of rubber-insulated lineman’s gloves.  The gloves should be rated at 1000V AC (class 0) (Fig 1) and tested before each use. Some simple but vital cautions should be

observed when using lineman’s gloves. Because they are rubber and they will be used around metal, they could become damaged, and even a pinhole could allow high voltage in. Before they are used, they should be checked for leaks by rolling them up from the cuff and inflating them (Fig 2). Also, if they get wet or your hands are damp when using them, they may not provide the protection that is needed. I have even seen a recommendation that a second pair of work gloves be worn over the lineman’s gloves to protect them from damage while in use (Fig 3).

Figure 4

In Figure 4, orange high voltage gloves are being worn for electrical protection, with leather gloves over them to protect the electric gloves from damage as a high voltage fuse is being removed. Other PPE needed for HV vehicles are standby safety persons armed with a tool, which looks like a giant shepherd’s hook (Fig 5) that can be used to pull the technician away from high voltage danger, in case of emergencies. High voltage wires have been marked with a bright orange outer sheath (Fig 6) to let anyone working on a vehicle know that they carry high voltage current. Caution should be strictly observed if the vehicle’s high voltage system is not disconnected.

Figure 5

Disarming a high voltage vehicle
Generally, the vehicle is always assumed to be live unless you have disconnected it yourself. The vehicle should have the key removed; many technicians place it on the dashboard so that it can be easily seen through the windshield (Fig 7). Before removing the key, one should check the high voltage malfunction indicator lamp (MIL), which is usually separate from the engine MIL. This may indicate a malfunction in the high voltage system that will need to be investigated. The parking brake should be set and all the trim removed to access the high voltage disconnect switch. The high voltage switch and cables are marked with bright orange color for ease of identification. This Ford Escape switch is round

Figure 6

and found in the back hatch (Fig 8). With personal safety equipment on, the technician can rotate the switch to the left to the unlocked position and then lift it to remove (Fig 9). Then it can be put back in the service shipping position to keep debris out during repairs, and the vehicle will have no voltage coming from the HV battery. Switches on other vehicles, such as the Toyota in Figure 10, are also easy to find and disable. On this one, the lever is pulled down and then pulled straight out (Fig 10).

Even after the switch is off and high voltage is blocked by system condensers, technicians should maintain a waiting period followed by checking with a high voltage meter to confirm that the system is safe before any additional work is performed. If the vehicle has been damaged and the switch in the back is unreachable, most vehicles can be disabled by removing a fuse, (Fig 11) relay or service plug. This alternative method can be found in a vehicle’s service manual.

If the HV MIL was on before the system was disconnected, the HV wires should be checked for breaks, cracks and potential shorts. The wires are all bright orange and on the underside of the vehicle, with a plastic protective cover over the orange wire protector. If the high voltage wire is in need of repair, the manufacturer’s recommendations should be followed. Most recommend not using vinyl electrical tape for permanent repairs. The specific vehicle’s service manual should always be consulted.

Figure 7

Heat effect on HV batteries
The next precaution is one that many may want to disregard. However, it not only is physically dangerous, but if the precaution is not followed, it also may severely impact the HV battery life

expectancy. High voltage batteries, especially Nickel-Metal Hydride (NiMH), are sensitive to heat. In fact, on some vehicles, a separate air conditioner system is installed to cool the battery during normal operating conditions (Fig 12). Because of this sensitivity, the manufacturer recommends that the HV battery be removed before the vehicle is placed in the paint booth. Most HV batteries are heavy and difficult to remove, often needing special lifting tools and always with very

Figure 8

specific directions so that the expensive ($4,000 and more) battery is not damaged. Also keep in mind that although the battery is disconnected from the vehicle, high voltage remains stored in it, and caution must be followed. Intuitively, a vehicle that is painted but not baked should not overheat the battery if heat is the only condition at work. A call to the manufacturer’s tech line for confirmation is a prudent alternative. Most of the recommendations have been changed to not have the temperature exceed 140 degrees F for more than 40 minutes. An alternative is to let the vehicle cure without baking. Of course, the vehicle manufacturer’s recommendations should be read, understood and followed.

Figure 9

Regenerative braking systems
A regenerative braking system is a way of slowing a vehicle and converting the kinetic energy into another form of energy, which could be immediately used or stored into energy to be used later. In other words, instead of slowing a vehicle by applying friction to the wheels as in a normal hydraulic braking system, the vehicle is slowed by using the forward movement to turn generators on the wheels to produce electric power that is stored in the HV battery. Though this is a great advantage in energy savings, it can pose a problem for a disabled vehicle. An EV or HEV vehicle that is pushed in a shop will generate electricity and pose a potential danger to persons around it, even if the battery is disconnected. Therefore, if a vehicle must be moved, the wheels should be placed on a dolly so it can be moved without turning the wheels.

Figure 10

Acid vs. alkaline batteries
Though we have become very accustomed to lead acid batteries and how to neutralize them with bicarbonate soda (common baking soda); the batteries in some hybrids, such as Nickel-Metal Hydride (NiMH), are alkaline, and pose as much of a health hazard as lead acid. Therefore, an alkali- and acid-resistant face shield needs to be worn in addition to your safety glasses. Some recommendations state that if any fluid leaks that is suspected to be battery electrolyte, synthetic rubber coveralls or an apron and boots should be worn, along with the lineman’s gloves and face shield. The fluid could be acid (from the 12V battery) or alkaline (from the HV battery), and unidentifiable until it is tested.  Each requires different neutralizing and cleanup. If a battery leak is suspected, a respirator should be worn and a fan used to remove the potentially explosive gasses. The vehicle’s high voltage system should be disconnected before cleanup or any other work is performed.

Once it is confirmed that the vehicle has been disabled, the battery leak can be tested,

Figure 11

neutralized and cleaned up. First, while wearing protective equipment, the technician needs to test the fluid with litmus paper by dipping the paper into the leaking fluid. If the fluid is acid, the paper will turn red and when compared to the chart will give a number from 6 to 0. If the paper turns blue and results in a match from 8-14, it is base, or alkali. An acid spill, such as with the 12V battery, is neutralized with baking soda or ammonia. If the spill is alkali, it is neutralized with boric acid or vinegar. Once the spill has been neutralized, the remaining liquid can be cleaned up and disposed of according to local, state and national restrictions.

Figure 12

Though these many procedures and precautions might sound complex and cumbersome, it truly is no more difficult to protect yourself from the risks of a hybrid vehicle than it is to protect you from isocyanides in paint. With a little investigation, training, some added safety equipment and a few new tools, soon we will be repairing hybrid vehicles like they were old school.

However, keep in mind that the repair procedure becomes truly dangerous as we become accustomed to the dangers and possibly lax with our safety precautions. So, as I have been telling my fellow workers for the past 40 years,  “Let’s go to work, and be safe out there.  I want to come to your 100th birthday party!”

About the Author

Al Thomas

Alfred Thomas is associate professor and department head of Collision Repair at Pennsylvania College of Technology. His technical experiences include 15 years in the collision industry as a technician and shop manager, 12 years as a secondary vocational instructor, and the past eight years as lead instructor at Penn College.

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