What are the safety problems of high-voltage work in electric car repair workshops?

1. Safety management of high voltage maintenance workshop
In addition to the safety requirements of ordinary workshops, there are also some special precautions for the safety management of high-voltage maintenance workshops dedicated to electric cars.

(1) car welding maintenance
①First, cut off the low-voltage power supply and unplug the power battery.
②The operator must have a special operation certificate.
③ Clean up the surrounding flammable materials and apply for a hot work permit.
④Protect the car body to prevent splashing and fire.
⑤ Operate in strict accordance with the welding process.

(2) Use and inspection of fire extinguishers
①The occurrence of fire will cause immeasurable harm. Therefore, it is necessary to prevent the occurrence of fires such as car spontaneous combustion, and promptly deal with hidden dangers such as oil pollution, loose connectors or aging wiring harnesses in the engine room.
② Don’t panic after a fire occurs, and take correct measures to put out the fire in time to eliminate the fire in the bud. First cut off the power supply, all personnel immediately leave the car and stand in the windward position away from the car.
③ Always check whether the fire extinguisher on the car is in a fixed position and whether it is within the validity period. To fully understand the nature of this fire extinguisher and the correct use method. Immediately call the police (Tel 119, 110) while taking fire fighting measures.
④ When a fire occurs in an electric car, the most effective way to put out the fire is to use a large amount of water to put out the fire. Because electric car fires are mostly caused by short circuits, in this case, in order to ensure the safety of personnel, the use of water-based fire extinguishers can quickly reduce the heat generated by the short circuit, so that the electric energy is exhausted to effectively extinguish the fire.

2. High-voltage workshop site and facility requirements
The quality of the working environment will directly affect the probability of accidents. The site and facilities of the electric car high-voltage maintenance workshop are higher than that of the ordinary automobile maintenance workshop. Figure 1 shows the layout of a typical electric car high-voltage maintenance workshop.

What are the safety problems of high-voltage work in electric vehicle repair workshops?
Figure 1 Layout of a typical electric vehicle high-voltage maintenance workshop

(1) Usable area
The area of ​​the high-voltage maintenance workshop is determined according to the actual requirements and conforms to the relevant national regulations.

(2) Lighting
A bright workshop allows car maintenance personnel to observe the surrounding components and objects more clearly, avoiding accidents caused by accidental contact with high voltage due to poor vision, and also helps other personnel to observe possible hidden dangers in time.
The lighting of the maintenance workshop shall comply with the relevant provisions of GB 50033–2013 “Architectural Lighting Design Standards”. Lighting design should pay attention to the direction of light, and should avoid occlusion and unfavorable shadows to the work. For places that need to identify colors, lighting materials that do not change the color of natural light should be used.

(3) Lighting
When natural light is insufficient, artificial lighting sources should be configured. The artificial lighting source should choose a light source that is close to the color temperature of natural light. The lighting requirements of the maintenance workshop shall comply with relevant regulations. The illuminance of the work area of ​​workbenches, instruments, equipment, etc. for fine operations (such as scribing, metal finishing, gap adjustment, etc.) should not be lower than 500lx. When the illumination is insufficient, local supplementary lighting should be added, and the supplementary lighting should not produce harmful glare.

(4) Drying
Drying is to reduce the risk of electric shock to personnel in the service area. Because when the humidity increases, the insulation resistance of the human body and the air decreases, and at the same voltage, the risk of electric shock to the human body also increases. Therefore, the high-pressure workshop must be kept dry.

(5) Ventilation
Ventilation is conducive to the discharge of harmful substances generated during car maintenance, and in the event of an electric shock accident, a ventilated environment is more conducive to the injured person to breathe fresh air. Ventilation should meet relevant requirements.

(6) Fireproof
Fire protection shall comply with relevant regulations.

(7) Hygiene
Hygiene should meet relevant requirements.

(8) Safety signs
Safety signs should meet relevant requirements.

In addition, for the maintenance of high-voltage cars, many manufacturers have special requirements for maintenance stations. For example, BYD Auto requires a separate maintenance station when repairing its new energy cars. The equipment of this station adopts special colors and other stations. the difference.

When there is a high-voltage car on the workstation for maintenance, obvious warning signs must be arranged around the workstation to avoid danger caused by others not being allowed to enter the high-voltage workstation. Figure 2 shows the high-voltage warning signs formulated by some enterprises.

What are the safety problems of high-voltage work in electric vehicle repair workshops?
Figure 2 High voltage warning sign

(9) High-voltage safety protection regulations
①Safety regulations.
a. Disconnect.
b. Prevent reconnection.
C. Make sure it is in a no-voltage state.
d. Ground and short circuit.
e. Cover or block adjacent live parts.
②Personal protective equipment should be used. Appropriate personal protective equipment should be provided to maintenance personnel for work in the workplace.
③The requirements of the maintenance site should be followed. To avoid danger or damage, the car must be parked in a clean, dry, grease-free, spark-free location and avoid being too close to other car repair stations.

3. Layout of high-voltage maintenance stations
The layout of the high-voltage maintenance station shall meet the following requirements.
① Dedicated maintenance station.
②Clean, dry and well ventilated.
③ Please set up a safety isolation warning before maintenance work.
④The maintenance station must be equipped with protective equipment.
⑤ Avoid unrelated people approaching.

4. Requirements for workshop maintenance personnel
①Have the “Special Operation Certificate (Low Voltage Electrician Certificate)” issued by the State Administration of Work Safety.
② Must go through relevant new model training and pass the assessment.

5 High-voltage maintenance operation standards
Electric cars involve high-voltage electricity, and the maintenance process must be carried out in accordance with the work flow in order to protect the safety of operators and the safety of cars and equipment.

(1) Specifications for electric car maintenance
When maintaining high-voltage cars, you must follow the high-voltage safety operating rules and motor car maintenance operating rules.

The high-voltage safety operation and maintenance specification is shown in Figure 3, which includes the following contents (warning signs, insulating shoes, insulating gloves, insulating caps, insulating tools, goggles, guardians, and employment certificates)

What are the safety problems of high-voltage work in electric vehicle repair workshops?
Figure 3 High-voltage safe operation and maintenance specifications

① For the high-voltage parts removed during the maintenance of the car, an obvious “high voltage do not move” warning must be immediately marked, and it is forbidden to place the parts with high voltage in an unattended environment.
② During the maintenance of high-voltage cars, it is forbidden for maintenance personnel to carry metal objects such as watches and metal pens.
③ Non-professionals are strictly prohibited from removing and installing high-voltage components.
④ Maintenance personnel who have not received high-voltage safety training and obtained a license are not allowed to carry out maintenance and other operations on high-voltage components.
⑤ It is not allowed to disassemble and repair high-voltage components during the charging process of the car.
⑥ High voltage disable operation must be carried out before maintenance.
⑦Before turning on the power after maintenance, make sure that there is no operator in the car.
⑧ After replacing the high-voltage components, check whether the grounding is good.
⑨The cable interface must be tightened according to the standard torque.
⑩ During the period of car maintenance, there must be two personnel with employment certificates to work at the same time, one of whom is the guardian of the work, and his job responsibility is to supervise the whole process of maintenance. If an electric shock accident occurs, the guardian should immediately take effective measures for first aid.

(2) High pressure disable operation procedure
Before dismantling and servicing the high pressure system, the high pressure disable procedure must first be performed. The high voltage disable operation procedure is as follows.
①Remove: Remove all external power sources from the car, including the 12V battery charger.
②Pull out: Pull out the charging gun.
③Off: Turn off the ignition switch and put the key in a safe area.
④Disconnect: Disconnect the negative electrode of the 12V battery and keep it away from the negative electrode area.
⑤Remove: Take off the MSD (manual disconnect switch) and put it in a safe area.
⑥Wait: Wait for 5 minutes to ensure that the high-voltage energy is fully released.
⑦Check: Check whether the operator wears personal safety protection equipment, remove the high-voltage connector, and start the next step of voltage verification.

(3) Precautions for electric car rescue when going out
When going out to rescue a broken down electric car , you should pay attention to the following matters.
① When the car is active, move the car to a safe area that will not affect the passage of other cars.
② Turn on the double flashing warning light when conditions permit (it can also be replaced by a luminous body at night).
③ Immediately and correctly place the warning triangle according to the specified distance.
④If it cannot be repaired on site, please use hard connection to tow the car back to the repair point.
⑤ If it is determined that it cannot be moved, please contact the rescue car.
⑥ While waiting for rescue, all personnel should not stay in the car.

(4) Regulations on maintenance of cars
① Prevent the car from moving back and forth.
②Remove the key from the key switch lock before performing work in front of the car.
③ When carrying out work in the front cabin, be sure to use the fender pads.
④When working under the car, the negative electrode of the battery must be disassembled.
⑤ When jacking up the car, do not put it on the power battery.
a. Do not work under a car supported by only one jack.
b. The lifting requirements provided in the maintenance manual are applicable to the whole car. For a car whose drive motor or power battery is removed, the center of gravity changes, which makes the lifting situation unstable. At this time, the car should be supported or fixed on the lifting equipment. .
⑥ Do not leave tools and replaced accessories in or around the work area, and keep the work area clean and tidy.
⑦When welding on the car, the battery wiring must be removed to avoid damage to related parts, and the surrounding area should be equipped with appropriate fire-fighting equipment.

(5) Towing cars (take BAIC electric cars as an example)
If it is necessary to tow the car in a towing situation, use the following method. In order to be able to tow the car, a tow ring must be installed first, which belongs to the car-mounted tool.
The installation steps of the front tow ring are as follows:
①Pry out the traction ring cover: as shown in Figure 4 (Note: work carefully to prevent the paint surface from being damaged).

What are the safety problems of high-voltage work in electric vehicle repair workshops?
Figure 4 Prying Out the Tow Ring Cover

②Installing the traction ring: As shown in Figure 5, screw in the traction ring 1 in the direction of the arrow, and tighten it with the wrench 2.

What are the safety problems of high-voltage work in electric vehicle repair workshops?
Figure 5 Installing the tow eye

③After use, unscrew the tow ring and put it together with the on-board tool, and install the tow ring cover.

A note about “pulling and pulling” as follows:
①It is necessary to pay attention to the laws and regulations concerning car towing.
② Both drivers must be familiar with the characteristics of the towing process, otherwise the towing start or towing work cannot be performed.
③ If a traction rope is used, the driver of the tractor should pay special attention to operating the clutch slowly when starting and shifting gears.
④The driver of the towed car should pay attention to keep the traction rope tight at all times.
⑤ The hazard warning lights on both cars should be turned on and comply with regulatory requirements. The car key must be in the ON position so that the steering wheel is not locked and the turn signals, speakers, windscreen wipers and washers can be turned on.
⑥ The gear position of the towed car is in neutral, and the hazard warning lights are turned on. When the distance is long, the front of the car must be lifted. In the event that the transmission cannot be lubricated, it can only be towed with the drive wheels lifted.

(6) Jump start
Jump starting is not recommended, but in some cases it is the only way to start the car. In this case, the auxiliary battery after jump start discharge must be charged immediately to avoid permanent damage to the battery.

①Do not jump over the frozen battery, otherwise it will cause personal injury.
②Do not bridge the maintenance-free battery with black or white indicating window.
③ Do not bridge the battery whose electrolyte level is lower than the top of the plate.
④ Keep the battery away from open flames.
⑤ Put on goggles and take off the metal accessories on your fingers or wrists to prevent the battery from accidentally hitting fire and causing injury. ⑥ When using high-power starting equipment, do not make the battery voltage higher than 16V.
⑦The battery electrolyte is a corrosive solution, do not let the electrolyte come into contact with eyes, skin or clothes. Do not tilt the battery or allow the clips to touch each other when connecting the clips. If electrolyte splashes into eyes or on skin, rinse immediately with plenty of water.
⑧The battery may produce flammable and explosive hydrogen, so keep the flames or sparks away from the vent.
⑨ Do not use starting auxiliary battery or other starting auxiliary power supply with output voltage exceeding 12V.
⑩ When using another car to start, it is necessary to prevent the bodies of the jump-starting cars from contacting each other, otherwise the electrical system of the two cars may be damaged.

When connecting jumper wires to the battery, do not allow the jumper wires to touch each other or body ground. A fully charged battery, if it is short-circuited by the jumper, will discharge at a current higher than 100A, causing arcing and causing the temperature of the jumper and terminals to rise rapidly, and may even cause the battery to explode. Failure to follow these instructions could result in injury to the operator.