The annual rainy season is coming again. This time, not only the south will suffer from the problem of drying clothes, but also the heavy rain in the north will follow. In recent summers, I have seen many fuel trucks lying in the rain. Everyone joked that it was not a car but a boat in summer, and the owners of electric cars were shivering. After all, electronic components are more afraid of water. How many electric car owners looked at the weather forecast before going out and found it was rainy and snowy, so they gave up the idea of driving out. Then, is the electric car really so delicate that it will short circuit after soaking in water and even cause accidents such as fire?

Let's start with the conclusion: electric vehicles are not so "afraid of water" and even much better than fuel vehicles to some extent.

Let me talk about the shell structure of the battery pack first. Generally speaking, the shell of battery pack is made of carbon steel sheet metal box. After the sheet metal is stamped into parts, it is directly spliced and then spot welded. After molding, it must be reshaped and the surface roughness of the paint film on the connector installation surface must be maintained, all of which are to ensure the airtightness of the battery pack. At present, the most commonly used technology is aluminum profile extrusion+friction stir welding+cold metal transition (CMT) repair welding technology, and then welding is carried out at the position where air leakage or poor welding may occur.

In addition, when assembling the battery, a gasket should be added between the box covers to help form a more sealed structure. Gasket materials should have flame retardant properties, meet the standard requirements of prohibited substances in automobile industry, and avoid permanent deformation. In addition, the electrical connectors in the battery pack, especially the sealing design of the pin position, the smoothness of the connector installation surface, the permanent deformation of the O-ring and so on, will directly or indirectly affect the airtightness of the battery pack.

For the above configuration, firstly, the hard and waterproof shell material is selected, and the position that is easy to cause liquid leakage is welded during the processing, so the battery pack itself has been fully prepared for waterproofing. After the battery pack is produced, it will be tested by professional air tightness testing instruments to inflate the battery pack cavity. By observing the change of air pressure, the leakage value of gas will be calculated and the waterproof performance will be judged.

Simply put, the battery pack of electric vehicles, first of all, the shell has been strong and waterproof; Even if the shell leaks water in an accident, there is a gasket inside to protect it; Even if the shell and gasket fail, the device plug-in inside the battery has a sealed design and a three-layer waterproof design to ensure foolproof.

The General Administration of Quality Supervision, Inspection and Quarantine of China stipulates that the battery module should be fully charged, soaked in 3.5% NaCl salt water for 2 hours, and then observed 1 hour. During the whole process, the battery/battery pack is required not to catch fire or explode to ensure the waterproof safety of the power battery. In addition, the battery pack needs to be connected to the vehicle wiring harness in the assembled state, completely immersed in a water depth of one meter for 30 minutes, and it will not be officially delivered until the result meets the requirements, which also ensures the quality and safety of the battery itself to the maximum extent.

Secondly, we should know that vehicles will be evaluated by the automobile safety evaluation system when they leave the factory, and most car owners are worried about the safety of wading. One of the indicators to measure the waterproof performance of batteries is called Ingress? Protection, abbreviated as IPxx, the first X stands for dustproof (solid) grade, and the second X stands for waterproof (liquid) grade. The following figure shows the evaluation criteria of each level:

At the same time, the protection level of many electric vehicles has reached IP67. The new national standard requires that vehicles should undergo simulated wading test before leaving the factory. Vehicles are required to travel at least 500 meters in a water depth of one meter, and the insulation resistance can meet the safety requirements in wet state. It will take 24 hours to meet the requirements and meet the standards. The depth of one meter here is not the depth of the road, but the depth without electronic equipment, which is almost equivalent to the situation that the car has completely sunk into the water. ?

For pure electric vehicles in the market, the battery pack should be flame-retardant structure coated with isolation film and equipped with pressure relief valve to ensure the safety of electric vehicles in case of sudden collision and other accidents. From the perspective of the whole vehicle, the vehicle also needs to be equipped with a battery management system. Once water enters the battery pack, the insulation resistance drops, and the power supply will be cut off in time to stop the vehicle and ensure the safety of passengers. ?

To some extent, electric vehicles are even more reliable than fuel vehicles in waterproof, which is caused by the working principles of the two models. ?

The fuel truck is powered by the engine, and the fuel needs to be mixed with air before it can be ignited. The operation of the engine needs air intake. To some extent, the cylinder of the engine is connected with the outside world. Once water enters the engine through the air intake structure, it will immediately turn off or even explode the cylinder. At the same time, because water can't be compressed and forced to start immediately after flameout, the engine connecting rod may be scrapped, which is why many fuel vehicles dare not move easily after crouching in rainy days. ?

On the other hand, the pure electric vehicle is powered by the battery pack, which is transmitted to the motor and electronic control through the high-voltage circuit, and the motor does not need air intervention. At the same time, the internal high-voltage circuit and the external part of the electric control device are equipped with independent shells or insulating materials to ensure absolute work safety. The battery, electronic control, motor and their connecting wires of pure electric vehicle are a closed system. ?

Therefore, the wading problem of pure electric vehicles is more from the damage of other parts when the vehicle encounters water. Under the requirement of compulsory waterproof standard, pure electric vehicles can actually work under the condition of flooding. Of course, being able to work is one thing. For the sake of safety, the owners of pure electric vehicles are still not allowed to continue driving when the vehicles are flooded. ?

So when it rains, can the electric car be charged with confidence?

The answer is yes. There is an insulating sealing ring at each hole of the charging slot of the pure tram. If a short circuit is caused, the hole of the charging port needs to be completely soaked by rain. Because the charging port is vertically arranged, it is difficult for rain to soak the charging port. Of course, the premise is that people will not see the charging port flooded and put the charging gun in it.

Although the high-voltage system components, high-voltage wiring harness and high-voltage connector of electric vehicles are required to reach IP67 waterproof and dustproof level, if a seal is aging, there is also the risk of water ingress. When charging, try to ensure that the charging port is dry to prevent condensation and charging safety problems. This also requires regular inspection, timely replacement of aging parts, and more attention to the chassis and braking system after wading.

Again, electric vehicles wading in water will not cause safety accidents, which does not mean that they can be used as submarines! Slow down when driving and wading. If necessary, you can get off and explore the water depth. It is best not to flood the chassis, which can not only protect the battery safety, but also protect the vehicle safety. Once the car is deeply immersed in water for a long time, it should be overhauled in time to avoid internal structure corrosion.

Charging in rainy days does not mean that you can be fully charged in the open air, but you can sit in the car and play games in heavy rain! Isn't that car faraday cage? I'm a little excited to think about it. It is best to park and charge in an open place and try to avoid low-lying places, which is also for the sake of vehicle life.

Therefore, electric vehicle owners do not have to worry too much about the safety of vehicles in flood season. Pure trams with IP67 protection level are even safer than fuel vehicles in rainy days, at least there is no need to worry about engine water. But again, the ultimate goal is to check regularly and use cars scientifically so that everyone's cars can stay with them for a long time.

This article comes from car home, the author of the car manufacturer, and does not represent car home's position.