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The electric and hybrid vehicle maintenance is, for several reasons, simpler when compared to the internal combustion engine vehicles. This technical article mentions the electric and hybrid maintenance and safety procedures, focusing the electrical system.
The major difference of both typologies of vehicles, on what concerns the maintenance, is the way that the power is delivered. For the electric and hybrid vehicles, the maintenance is simpler due to the electrical parts that composed the electric system. The benefits from the regenerative braking, the reduced quantity of moving components and fluids, means less costs associated to the maintenance of electric and hybrid vehicles.
Regarding the regenerative braking, the fact that the system recovers the kinetic energy associated to the vehicle motion, the energy that would dissipate on the brake pads and discs is converted in electric energy and stored in the high-voltage (HV) battery. Therefore, it is expected that not only the brake wear but also the costs associated are a lot less. However, it is important to be alerted to the brake system, in order to guarantee the safety for all vehicle occupants.
Concerning the fluids, the electric and hybrid components need less fluids to work and in most cases the maintenance is not necessary. Thus, some car manufacturers isolate the components, sealing it and making the fluids inaccessible. However, just like conventional vehicles, the HV battery coolant fluid, the braking fluids and the windscreen wiper fluid, must be maintained and verified in every maintenance procedures. In some car manufacturers the fluids from the gearbox needs to be replaced periodically.
The 12V battery is commonly used in all car manufacturers, including the electric and hybrid vehicles. In those vehicles the 12V battery supplies the HV system and secondary components of the vehicle, such as the on-board functions, windows, airbags and interior and exterior lights. Despite not being part of the manufacturer maintenance plan, this verifications must be guaranteed.
On what concerns the HV battery, this is not part of the maintenance intervals. However, as this component is responsible for the vehicle propulsion, it is important to guarantee that it is working properly. This component tends to be less efficient over time, however, the intervention in the HV battery is only recommended when the warning light shows up or when the vehicle has some anomalous behaviour. The HV battery intervention consists on replacing it for a new one or testing and replacing for new individual cells or internal battery modules.
The examples mentioned earlier led to the conclusion that, when compared to the traditional vehicle, the maintenance is simpler due to the fact that there is less components to be replaced or repaired. However, this does not mean that the technical capacity can be expendable. In terms of security during the intervention, also because of the electrical components of the vehicle, the safety procedures must be followed in order to prevent dangerous accidents.
Unlike traditional vehicles, the HV components can reach voltages up to 600V and can cause serious danger on the operators´ health. The danger is not caused directly by the high level of voltage but by the combination with other electrical factors and working condition, such as, the voltage with the electrical current, electrical effect, frequency, sudden variation of current, contact pressure and human body resistance. According to Ohm´s law and as it is showed in figure 1, the electrical tension (V) is the result of the body resistance (Ω) multiplied by the current intensity (I). This means that if the voltage is high, when combined with a reduced body resistance, led to a high current. On the opposite way, the bigger the body resistance or the contact resistance, for example rubber boots, the less current crosses the human body. So, the severity of the body damages is directly influenced by the combination of these factors.
The accidents with electricity can be avoided if correct precautions are taken into consideration. The operator should follow the recommended procedures avoiding the contact with the active parts of the materials or with electric components and also not touching mass cable that can accidently be electrified.
Meaning this, there is a list of measures that needs to be followed:
• Never touch in open components in an electric installation;
• Always confirm if the electric insulation is in good shape and never damage the cable insulation;
• Never pull the power providing cable to turn the system off;
• Do not create patched connections
Besides the usual safety procedures, the operators´ training and wearing of personal protective equipment’s (PPE), is essential.
The intervention on HV components must only be performed by level 3 technicians on medium and high voltage training.
Regarding the PPE, the intervention in HV components requires the usage of isolated equipment with high electric resistance. These equipment should be certificated and replaced in case of damage.
The gloves should be isolated and certified for “classe 0”, valid for 1 year. This means that the date of the first usage should be registered so the shelf life is not surpassed.
On what concerns the rubber boots, these should guarantee the SP3 certification. According to this certification, the boots cannot be made of any metallic material and the sole and toecap should be made of Kevlar or a similar non-conductive material.
Still in terms of security for the operator, it is recommended to wear glasses to prevent electrical arcs or battery chemicals’ and the glasses should be anti-fog.
As a complement to the PPE, the operator should follow the recommended procedures and use tools that personally protects the operator and that guarantees the deergenization of the vehicle.
All tools must be isolated to 1000V making possible to the operator to move and repair HV components.
Concerning the insulating blankets or mats, they are complementing the PPE too. The insulating blankets must guarantee insulating properties to over 1000V and the mats, which are used for damaged vehicles or interventions that indicate electrical problems, should guarantee insulating for 50000V.
In case of electrocution, it is needed the insulated rescue stick. This tool is used to rescue the operator in shock e should be composed of a non-conductive material with enough length to not occur electrical arc.
On what concerns the vehicle, before initiate any intervention in an HV component it is mandatory to put the vehicle in safety mode.
The working area fencing or safety barriers are the first procedures to be made before intervene the vehicle. According to figure 2 the retro-reflective warning signs must surround the vehicle whenever HV components are being moved or repaired. The working area surrounding the vehicle must be limited to 1,2m from the vehicle and marked with safety barriers, if possible with red and with stripes and not supported by water or any other conductive material.
During the intervention, the safety procedures should be followed in order to deergenizate the vehicle. It is extremely important that the procedures are executed by the following order:
1. Turn of the ignition and remove the key to an area where it cannot be detected by the smart key system (if applicable);
2. Remove the negative pole from the auxiliary battery;
3. Use the PPE, such as isolated gloves and footwear;
4. Locate and remove the safety lock (consult the car´s manual);
5. Wait for at least 10 to 15 minutes before the capacitors discharge completely;
6. Measure the voltage on the inverter´s terminal – 0V;
7. Isolate the HV connector with isolated tape.
Depending on the car manufacturer, the safety lock is located in different locations on the vehicle. By convention, all HV cables and safety locks are orange coloured.
In conclusion, in terms of maintenance, through the examples mentioned before, it is unmistakable that the after-sales companies from the future need to change their structure and rethink the intervention procedures in order to meet the market demands. The system´s characteristics lead to the necessity to adequate resources, training them about the specifications of each electrical components and, most important, about the safety procedures that need to be followed during the intervention. This article is available for consulting in: