Introduction to failure mode of electric vehicle power changing technology

Many people have some complaints about the Chinese government's choice of "pure electric" technology for new energy vehicles, mainly because power batteries must be equipped with a large number of charging piles, which cannot be widely used along the road. So some experts actively advocate that the only best technology is the current mode of electrical change.

The author has been studying the electric power supplement mode of electric vehicles for a long time. The research conclusion shows that compared with the charging mode, the electricity-changing mode is more technically difficult, with larger investment scale and more difficult to popularize, and basically hopeless in investment and recycling. The failure mode analysis of electric vehicle switching technology is carried out below for the reference of concerned peers.

1. Why does China propose the new energy vehicle development route of "overtaking on curves"?

Energy conservation and emission reduction is a common task faced by all countries in the world. The development direction of automobile is electrification, which is the common understanding of the automobile industry all over the world. However, the implementation is different, that is, different countries have significant differences in the technical route of developing new energy vehicles:

A) at present, in Europe, diesel power is mainly encouraged. Mercedes-benz, audi and other brand manufacturers choose more energy-saving diesel technology route;

B) for many years, Japan has mainly advocated hybrid power, that is, under the existing refueling infrastructure, actively promoted hybrid power technology route, and made proud achievements;

C) the civil vehicle market in the United States is greatly influenced by Japan, and its basic trend is now approaching the hybrid vehicle routes in Japan;

D) after years of exploration, the Chinese government finally decided to develop the technology route of pure electric vehicles as new energy vehicles.

In summary:

A) Europe, America and Japan are now advocating to tap the potential of fuel vehicles to improve the effect of energy conservation and emission reduction. The first step of the new energy vehicle route of the current automobile power is the hybrid electric vehicle. Second step fuel cell vehicle; Step three: pure electric cars.

B) after the Chinese government experimented with hybrid technology, the final choice proposed by the Chinese government is the technical route of pure electric drive vehicles, that is, to adjust the technical route of the original vehicles and mainly promote pure electric (including plug-in hybrid) vehicles and then fuel cell vehicles.

The Chinese government put forward the basic reasons for the technical route of "overtaking on curves" :

First, the automobile development path in the past was dominated by Europe, America, Japan and other powerful countries, and China was a follower.

Second, China is now a big country in automobile production and consumption. As a follower, China has not become a powerful country in automobile industry through 30 years of efforts, but it lags behind in technology for a long time.

Third, the development of new energy vehicles, if continue to develop along the road developed countries, China will still not become a car power.

In other words, China already has the "" bottom gas" "to map out the development path of new energy vehicles. Can the development of Chinese automobile make China a powerful country? It is too early to say for sure. However, the fact that China's production and sales of new energy vehicles have exceeded 500,000 in 2016, making it the world's first major producer of new energy vehicles, shows that China's new energy vehicle industry has entered the fast development channel.

Second, the development of electric vehicles, vehicle battery energy supply?

The vehicle-mounted battery system is an energy storage component, and its energy supply mode is basically divided into two categories. The second is to rely on the ground power grid to car battery power supply. There are two ways of power supply from the power grid to the battery:

A) switching mode. On the ground to charge the battery, then charge the battery to the car, and then the "empty" battery for a down, to charge;

The analysis of failure mode of power changing technology since battery can't be separated from vehicle

B) direct charging mode. The vehicle-mounted battery is recharged after it is connected to the power system of the power grid through the charging gun (charger).

For the battery, whether it is in the mode of power change or directly charging the car battery through the charging gun (device), it is a power supplement. Different from the charging mode, the power changing mode can realize factory charging production, and can charge the battery in a concentrated and batch manner. Charging is like processing. The battery to be charged is better than the material to be processed.

In the battery factory-type charging mode, the charging time of electric energy is borne by the charging factory, while the time to directly charge the car battery is borne by the owner. Battery charging is an electrochemical process, while refueling is a physical process. As a general rule, the speed of electrochemical reaction is much faster than that of physical refueling simply for the speed of electric energy replenishment. But the speed of electrochemical reaction is too fast, and the cost of security measures is quite high. So in fact, the battery charge time is much longer than the refueling time, is based on the battery power supplement security fastidious. In layman's terms, battery power is many times more technically complex than physical fuel.

Iii. What kind of mode of electric energy supplement can satisfy electric vehicle users?

From the perspective of car users, it is required that the waiting time for electric cars to replenish their electric power should not be longer than the time for fuel cars at gas stations. The premise here is that increasing satisfaction does not increase spending. User satisfaction is a subjective feeling.

The current confusion is that the user has already had the experience and is basically satisfied with the refueling time. If the electric vehicle power replenishment time does not reach this level, users will certainly not be satisfied with this indicator.

In terms of technology, it is feasible to improve the supplemental efficiency of electric energy, no matter it is power changing technology or direct charging technology. However, it must increase the cost of improving the power supply efficiency. If the cost is borne by the user, the user will not be satisfied. From the perspective of user satisfaction, is there an ev energy replenishment mode that takes less time than refueling without increasing user expenditure? To be sure, no!

Technically, charging technology can improve the power supplement efficiency, but if the power supplement efficiency increases a little, the cost will increase exponentially. Of course, power changing technology can also improve the power supplement efficiency. The greater the efficiency is, the greater the cost and expense will be compared with that of charging technology.

Who will bear the cost of this increased efficiency? There is no main body to bear the efficiency cost of this electric energy supplement, and it has no economic significance to popularize the high-efficiency electricity changing technology or the high-efficiency charging technology.

Iv. Questioning of the news events reported by CCTV

CCTV carried a report on an enterprise in southwest China, which actively promotes the electric-changing technology. Its theme is "electric-changing technology", which can realize 5 minutes to complete the electric power supplement for electric cars. In other words, how is the electric changing technology more advanced than the charging pile technology?

The picture is that after the car adopts the power changing mode, the car is out of power. The owner service provider makes a phone call, and the special car for battery change arrives immediately. Two professionals change the battery and drive away in less than 5 minutes. The author makes logical deliberation as follows:

Premise: it's not the car that breaks down, it's just the car that's out of power.

Repeating:

A) if the fuel vehicle runs out of fuel, can you make a phone call and bring a fuel tank with the special vehicle to replace the original fuel tank? Technically, yes; But if the dedicated service vehicle with a small amount of fuel, to the car tank with a certain amount of oil? Which service are users more satisfied with?

B) if it is the charging way, can you make a phone call and come to a special car to charge the car without electricity for 10 to 20 minutes? Is the user satisfied with the power change or charging mode?

Is it better to change power mode or charge mode? Shall we continue the discussion?

V. comparison of power changing mode and refueling mode

The technical difficulty of changing electricity is much greater than that of refueling. The oil is liquid, can be transported through the pipeline, the tank is fixed to the car. There are safety requirements for fuel tank installation. Similarly, there are safety requirements for the battery case to be mounted on the vehicle. The installation technology level of car battery box is much higher than that of cell phone battery and electric bicycle battery box. The cell phone battery and electric bicycle battery box can be designed as plug and play parts. The car battery box is not allowed to be a plug and play parts, high-voltage electrical equipment installation is the installation requirements, one is mechanical, the other is electrical performance requirements. On-board power battery installation is by no means a loading and unloading process of on-board cargo.

In the practical example of power changing mode reported by CCTV, after the battery box is installed on the car, the battery box can be fixed by tightening the battery with a sliding soft belt. Its propaganda is no bolts, no nuts, no spanner. It seems simpler than installing plug-and-play components on a PC motherboard. In fact, plug and play is installed on the computer, but also to be fixed with a screwdriver.

The author questions:

A) when are national and industrial standards allowed for such installation? Advertising is ok, engineering is absolutely not allowed;

B) the installation reliability of automobile assembly parts shall be measured by tools and must meet the requirements of technical level, otherwise, its safety cannot be guaranteed.

C) dangerous goods in the vehicle-mounted power battery box, with high voltage on it, shall not be operated by non-professional personnel, and must be provided with technical support of preventive measures against mistakes. If you want to improve its safety installation efficiency, must be equipped with more professional equipment and professional personnel.

D) at present, the owners of oil-fueled vehicles can refuel themselves at gas stations, which improves customer satisfaction. Can the power change mode be self-service?

Six, some experts in the promotion of electrical technology often make common sense mistakes

Common sense error 1: charging pile charging is misguided. In fact, charging technology is the basic technology to recharge the battery of electric cars. For example, tesla electric cars are also charging mode. Why is charging electric cars with charging piles in China misguided?

Common sense error 2: it's a fantasy to popularize charging with charging piles. In fact, China's charging pile technology has been very mature. Having alternating current or direct current; Having a charging gun or a charger; There are centralized charging stations and individual chargers. At present, most of the 1 million new energy vehicles are in charging mode. Why whimsical?

Common sense mistake 3: separate the battery from the car, and replace the gas tank to meet the requirement of quickly replenishing electric energy.

"Batteries and cars" cannot be separated. This is not a technical issue, but a safety management issue. Batteries and cars must be "one-to-one", not "many-to-many". There is a problem of attribution of safety responsibility for civilian vehicles. Who is the subject of safety responsibility? Gas tank out of the safety responsibility accident, the responsibility of the main body of the division is not difficult, civil vehicle development safety responsibility accident, how to divide the responsibility of the main body is very difficult. But military vehicles can. National standard (" motor vehicle operation safety technical conditions ") will not allow the electric changing mode of vehicles on the road. Gas cookers are not on the same level as electric cars.

Common sense error 4: group the batteries and discharge them one by one, replacing the used battery pack each time.

The batteries are grouped, but the system works as a whole. There is no principle of separate discharge. Can be charged separately, is to improve the charging efficiency, but there is no group for the principle of battery.

Vii. Research conclusions

A) power battery production and maintenance technology is very complex. Similarly the power battery electric energy supplement technology is also the high technology content.

B) charging pile (charger) is a basic mode to supplement electric energy of electric vehicles, which can be improved and improve its efficiency, but it cannot be overturned.

C) both charging technology and power changing technology can overcome some technical bottlenecks to improve customer satisfaction, but the input end must be low-cost and the service price provided is acceptable to users.

D) electrical changing technology costs more, and users will not bear high costs for this high-level service. No matter what kind of high-tech and high-level power exchange mode factory is built, it is impossible to get the expected return from ev users in terms of its input cost.

E) under the premise that the power battery energy is more than 100 times worse than that of fuel oil, the popularization of power changing technology will complicate the simple problem.

The page contains the contents of the machine translation.