With a number of OEMs declaring that they will only produce and sell EVs and will cease the production of gasoline-powered vehicles in the not-too-distant future, the chance of an EV showing up at your shop increases every year. If the vehicle is in for some repairs on minor scratches or a few door dings, not much will change in the way the vehicle is taken into the shop and processed before work starts on it. But what if the vehicle has been involved in a significant collision? This is where the handling of an EV will differ greatly from a gasoline-powered vehicle and where training is going to once again be critical for everyone involved. Most of today’s EVs, including hybrids, use lithium-ion batteries. There are millions of these batteries in service with a very low failure rate. However, in some circumstances, HV batteries may experience cell failure due to damage or other faults that can result in unsafe conditions.
It is if the utmost importance that proper Personal Protective Equipment (PPE) is used when high voltage is involved. This is not a recommendation; it is a must as the technician’s life is on the line. Only properly trained HV technicians who are familiar with the specific vehicle and the HV parts location should perform the initial inspection.
The initial intake or receiving of the vehicle is where it all begins. This is an initial inspection of the vehicle once it arrives at the repair facility. This is not the estimating or blueprinting process, that will come later. This is a first look at the vehicle for damage to the areas of the vehicle where HV system parts, cables, modules, etc. are located to see if the collision caused any damage to any HV system parts that can cause the potential for electrocution or a fire if not identified.
One of the first things to inspect is the condition and stability of the HV battery. First and foremost, always assume the HV battery is fully charged and that the parts of the HV system are fully energised. HV batteries have potential risks not just of an electrical nature, but due to their composition, there are chemical and thermal risks as well.
When inspecting an HV battery, look for evidence that the battery may be compromised. Some are obvious such as tears, punctures, or ruptures to the battery. Others may be less obvious, such as smoke residue, unusual sounds, or abnormal odours. In addition, look for discoloration, deformation, melted seals or connectors, or metallic splatter.
If an HV battery is compromised, or suspected of being compromised, certain precautions must be taken as a compromised battery has an inherent risk of overheating. This is due to the introduction of oxygen and moisture into the battery. This causes the battery components to oxidise, causing a heat reaction that can get excessive and cause the battery to combust.
The normal reaction in the battery produces heat and a coolant is used to keep the operating temperature of the batteries at an acceptable level. If there is a loss of this coolant and the heat builds and cannot be dissipated sufficiently, the battery can ignite. In addition, thermal runaway may occur when there is physical damage to a cell, overcharging, excessively high cell temperature, or an internal defect causing a short circuit inside the cell.
A burning lithium-ion battery will not easily be extinguished and can reignite. Calling the fire department in the event of an HV battery fire is a necessity. Keeping a safe distance and staying up wind of the fire will reduce exposure to the toxic chemicals and gases generated by the combustion of the battery and the rest of the vehicle.
As eluded to earlier, fire is not the only risk associated with a compromised HV battery. The electrolyte of lithium-ion batteries is not acidic, however, if the electrolyte leaks from the battery and it can pick up moisture from the air or come into contact with water and create hydrofluoric acid which is a strong acid that can cause severe burns. In addition, hydrofluoric acid and hydrogen fluoride gas are both produced when the battery combusts. This gas is poisonous, can be inhaled and absorbed through the skin, and can permanently damage the lungs and eyes.
This leads us to the next item to consider during the intake of an EV, storage. If the battery is compromised or the status of the condition of the battery is in question, it is best to store the vehicle outside “quarantined” at least 50 feet from structures, overhead wires, or other vehicles. A “Danger High Voltage” sign should be placed on the vehicle and remember not to roll the vehicle on the wheels as this can generate voltage to the battery system.
In the event of a battery fire, this quarantine will prevent adjacent structures or vehicles from catching fire and will also prevent the dangerous concentration of hydrogen fluoride gas inside a structure. Again, immediately call the fire department at the first sign of an HV battery fire. Keeping a safe distance while staying up wind of the fire will reduce exposure to the toxic chemicals and gases generated by the combustion of the battery.
Once a vehicle has been inspected and deemed safe by a certified HV technician, a pre-scan of the vehicle should be conducted to determine if there are any diagnostic trouble codes (DTCs) that indicate any unseen or underlying issues with the electronic system. The technician performing the scan should understand the codes that relate to the HV system. Some codes may identify issues such as loss of isolation, system interlock loop, or other HV system issues. These conditions may present a safety or electrocution hazard.
If no HV related DTCs are present, additional scanning can be done to observe live data of the HV system. Again, this should only be performed by a trained EV technician. The live scan can reveal abnormal variances in battery temperature or excessive voltage variations. Both of these occurrences may indicate a problem with the HV system.
As stated earlier, it is important for the HV technician to be familiar with the specific vehicle being inspected. In addition, it is important for the technician to know and follow all OEM specific procedures the vehicle maker has in place to evaluate and handle each EV. This includes battery disconnect and isolation procedures, as well as diagnostic procedures and checklists that will determine if a vehicle needs to be quarantined, or if other actions need to be taken.
Understanding the potential dangers of EVs and their HV systems, and having the training, equipment, and knowledge to properly service and repair them, including the initial inspection, is essential to a complete, safe and quality repair.
Author
DIRK FUCHS
Director
Technical Programmes & Services,
I-CAR
