Five steps to tame the dangers posed by these vehicles
STEP 1: TRAIN. So what should we do to stay safe around HEVs? Training is always a good place to start, specifically general training for hybrids through I-CAR or the vehicle manufacturer. You also will need a service manual since there are specific directions for finding the HV disconnect switch.
STEP 2: SUIT UP. Personal protective devices are essential. Arguably the most important is a set of rubber-insulated lineman's gloves (see Fig. 1). The gloves should be rated at 1,000V AC (class 0) and tested before each use. Observe some simple but vital cautions when using them. Because they are rubber and will be used around metal, they could become damaged. Even a pinhole can allow dangerous high voltage to pass through. Before using them, have them checked for leaks by rolling them up from the cuff and inflating them (see Fig 2). If they get wet or your hands are damp when using them, they may not provide the necessary protection. I've seen recommendations that after putting the gloves on, the technician should wear a second pair of work gloves over them to protect against damage to the rubber gloves.
Use an alkali- and acid-resistant face shield in addition to your safety glasses. Some recommendations state that any fluid leaks suspected of being battery electrolyte, should only be approached by a tech wearing synthetic rubber coveralls or an apron, along with boots and the lineman's gloves and face shield. Note: Until the spill is tested, assume that the fluid could be acid (from the 12V battery) or alkaline (from the HV battery). Each fluid requires different neutralizing and cleanup. If a battery leak is suspected, wear a respirator and use a fan to remove the potentially explosive gasses.STEP 3: POWER DOWN. Disconnect the vehicle's high voltage system before cleanup or any other work. The best way to disable the system is to follow the procedure described in a service manual.
Disabling the high-voltage system is a two-person job, according to some recommendations. One person wearing high-voltage protection safety gear disables the HV battery while a second technician with a long, oversized tool that looks like a giant shepherd's hook, stands by to yank the other away in case of mishap (see Fig. 3). An undrivable hybrid vehicle should not be moved with the drive wheel on the ground. The HV battery is so sensitive to heat that some manufacturers recommend that it be removed before the vehicle is painted in a booth (Ford TSB 04-17-14).
Always assume the vehicle is live until you have disconnected it yourself. 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, which you will need to investigate. Next, remove the key (see Fig 4). Many technicians place it on the dash so that it can be easily seen through the windshield.
Set the parking brake and remove all the trim to access the high-voltage disconnect switch. The switch along with the cables are marked with a bright orange color for ease of identification.
The Ford Escape switch is round and located in the back hatch (see Fig. 5). While wearing the appropriate safety equipment, the technician can rotate the switch to the left to the unlocked position and then lift to remove. It can then be put back in the service shipping position in order to keep debris out during repairs, and the vehicle will not have any voltage coming from the HV battery.
Other switches, such as ones found on Toyotas, also are easy to find and disable (see Fig. 6). On this one, the lever is pulled down, and then pulled straight out.
Though the switch is off and no high voltage is getting to the system because of the system condensers (see Fig. 7 where there are three condensers), you still need to complete both a waiting period and a follow-up by checking with a high-voltage meter to confirm that the system is safe. You need to complete this before performing any additional work. If the vehicle has been damaged and the technician is not able to get to the switch in the back, most HEVs can be disabled by removing a fuse, relay or service plug. This alternative method can be found in the vehicle's service manual. Some vehicles are equipped with an inertia switch (see Fig. 8). In some models there is more than one switch.
STEP 4: IDENTIFY AND CLEAN. Once you confirm the vehicle has been disabled, test and neutralize the battery leak, then clean it up. With your protective equipment on, test the fluid with litmus paper by dipping the paper into the leaking fluid. If the fluid is an acid, the paper will turn red. Compare the color to the litmus chart, which will rate the acid on a scale from 7 to 0. If the paper turns blue, you know it is a base and alkali and will register anywhere from 8 to 14 on the chart.
Neutralize an acid spill, for example a spill from the 12V battery, with baking soda or ammonia. Neutralize alkali spills with boric acid or vinegar. Once the spill has been neutralized, clean up and dispose of the remaining liquid according to the local, state and national restrictions you adhere to at your shop.
If the HV MIL was on before the system was disconnected, check the HV wires for breaks, cracks and potential shorts. The wires are all bright orange and on the underside of the vehicle, covered with a plastic protective cover over the orange wire protector. If the high-voltage wire is in need of repair, follow the manufacturer's recommendations. Most recommend that vinyl electrical tape not be used for permanent repairs.
STEP 5: STAY COOL. This last step is one that many may want to disregard. However, if not followed, you may severely impact the HV battery's 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 (see Fig. 9). 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 requiring special lifting tools and very specific directions to avoid damaging the expensive ($4,000 and more) battery. Also, though the battery is disconnected from the vehicle, high voltage remains stored in it, and caution must used when moving the battery. Contact the manufacturer's tech line for information before moving the battery or placing the vehicle in a paint booth.
Though all of these cautionary measures may seem overly complex and cumbersome, it's actually not much different than the steps shops took to protect workers when Isocyanates were introduced into paint systems. With a little investigation, training, some added safety equipment and a few new tools, you can soon be repairing hybrid vehicles like they were "old school" — though you don't want to become so comfortable you forget about the dangers they pose.
Keep in mind what I've been telling my fellow workers for the past 30 years, "Let's go to work and be safe out there. I want to come to your 100th birthday party."