Analysis on Route Problem of Power Battery Technology for New Energy Passenger Car

The new energy vehicle power cell has a long history of controversy over the safety of three yuan and lithium iron phosphate. In particular, there have been different opinions on which type of battery should be used for commercial electric vehicles. Therefore, the author aims at the technical route of the new energy passenger car power battery. Special appointment to Wangzidong, director of the National 863 electric vehicle special power battery testing center.

The following content is written by Wangzidong.

Electric buses have caught fire from time to time, which has attracted much attention from the industry. These incidents are a reminder that there are still many problems with new energy vehicles. The road is still long and the industry should always keep a clear head. In particular, it is not possible to say that power batteries are not good at the first safety accident. This is a problem that the entire new energy automotive industry must face together.

Wangzidong: The Route of Power Battery Technology for New Energy Passenger Cars

Five major factors of battery insecurity

The cause of the bus fire in Hong Kong in December 2015 was apparently caused by power batteries, but the cause of the battery heat runaway is uncertain. The group technology, charging method, use method, maintenance method, reliability of the protection system, and effectiveness of the communication protocol of the electric vehicle battery will all have an impact on the safety of the battery. In my opinion, these problems are mainly reflected in the following five aspects, resulting in the current production and sales of new energy vehicles and the number of fire accidents show a high-speed growth trend!

The first is that the vehicle company has not formed a reliable strategic cooperation relationship with the battery manufacturer for a long time. The power battery manufacturer is treated according to the purchase of parts and components, and has not carried out joint development work according to demand, and mutual loyalty is not enough. For example, in the past, the phenomenon of frequent pressure on the working capital of battery manufacturers by vehicle manufacturers was serious. It was difficult for battery manufacturers to fully consider the entire vehicle enterprise, and they would not develop suitable products for vehicle manufacturers. Due to the tight working capital of power battery manufacturers, Often, materials suppliers are also owed money, and materials suppliers are also considered for their own interests. They often do not give the best materials to battery manufacturers. It's a safety risk!

Secondly, because of the excessive price reduction of the vehicle company, the battery manufacturer does not have enough profits, so the service is not in place. Although there is corresponding data accumulation, it does not analyze. There is no interest in investing manpower and material resources in the development of a fault diagnosis system for the vehicle company, so it has not been able to detect the accident in advance.

Third, new energy car fires mainly focus on electricity and heat. In the process of research and development, companies in various fields such as pack, motor, electric control, and complete vehicles generally lack deep technological accumulation, and some enterprise product development processes with poor capabilities are not perfect to meet basic functions. The characteristics of new energy vehicles and components are not studied in sufficient depth, especially in the design of safety functions. Without effective verification, it is difficult to control the thermal runaway of batteries.

Fourth, the link structure in the high-pressure system is unreasonable and unreliable, which also leads to the occurrence of these accidents.

Fifth, the daily rational use, maintenance, maintenance and safety monitoring of vehicles are not in place, resulting in too much load on batteries. When small problems occur, they can not be adjusted in time, causing problems to be superimposed, leading to safety accidents.

The safety of passenger cars is related to the safety of life and property of more people, and the risks cannot be ignored. At present, lithium batteries are in short supply, and what kind of batteries can be sold, and the quality of products is declining, and the probability of accidents is increasing. With the passage of time, battery performance and quality are mixed, how to deal with the upcoming battery performance degradation, quality assurance, maintenance, complaints and other issues? All business and local government departments should be prepared for this.

In order to avoid the phenomenon of battery heat runaway, it is necessary to carry out targeted research and verification on the technology of group technology, charging method, use method, maintenance method, reliability and effectiveness of BMS protection system. In order to avoid the thermal runaway of the cell, improve the safety of the battery pack!

Dependency of Vehicle Enterprises and Battery Enterprises

Now that the new energy vehicles are so hot, it is recommended that the vehicle companies should develop and design new energy vehicles according to the user's use requirements and according to the performance of power batteries, instead of removing the engines and fuel tanks from the traditional vehicles and replacing them with motors and batteries. Become a new energy vehicle! In the current situation where power battery technology is not yet mature, it is necessary to select suitable application fields and areas that can provide business models to demonstrate operations, rather than developing in multiple fields at the same time as it is now.

As a power cell manufacturer, it is important to understand that the safety and cycle life of power cells on electric buses is the first, not the energy density. In particular, cluster technology, charging methods, usage methods, maintenance methods, and research on BMS protection systems that are related to battery safety improve active safety protection capabilities.

When developing products, enterprises should broaden their horizons and seek solutions to problems from multiple angles. Battery needs to be solved: meet the power demand of the working characteristics of the electric vehicle, meet the environmental adaptation requirements, meet the safety requirements for use, meet the reliability requirements, meet the fixed strength requirements, meet the reliability requirements of the electrical connection, meet the internal heat management requirements of the battery, and meet the battery Team leader life use requirements, meet battery rapid charging requirements, meet battery maintenance requirements, may meet battery rapid replacement requirements, meet low-cost requirements, meet the requirements for providing battery state parameters, meet the requirements for terracing utilization, meet the requirements for recovery convenience.

Vehicle companies need to consider long-term and stable strategic cooperation with power battery manufacturers. I suggest focusing on: companies that understand the power cell structure more thoroughly, do only power batteries, companies that are not too large, do not have liabilities, have better growth, have a dynamic business team, and have power battery products for export. It is recommended that when the vehicle company determines the power battery supplier, it will be arranged according to 1(world leading level): 1(domestic advanced level): 1(company that participates in the joint venture).

Is the electric bus suitable for lithium iron phosphate or Ternary?

Personally, I don't agree with the controversy between lithium iron phosphate and ternary material cells, and I think it is very unlikely that we want to make the power cell a safe and reliable commercial battery pack energy density of 160 W/kg in the short term! Because at present we can't even commercialize batteries with energy density of 100 Wh / kg. Why are we now going to argue about lithium iron phosphate and triple-material batteries who are good and who are bad? Where is our current ruler for the performance of a battery pack? It's not a national standard, it's an evaluation standard.

Some people say that ternary materials have a higher energy density than lithium iron phosphate. In fact, this "comparison" is unfair and there are incomparable factors. Lithium iron phosphate can be used for large capacity, and ternary materials can only be used for small capacity. I recommend that the comparison of energy density must be compared with the same battery capacity and based on the same safety and cycle life. Such as 100Ah, 200Ah.

Lithium iron phosphate has better life, high temperature characteristics, and safety than ternary materials. The low temperature performance is similar to that of ternary materials. The volume energy density of lithium iron phosphate batteries is lower than that of ternary materials.

Lithium iron phosphate and ternary material who can be used on which electric vehicle? It depends on the requirements of the electric car. The following table allows you to compare lithium iron phosphate and ternary materials from another perspective who are more suitable for electric vehicles.

Wangzidong: The Route of Power Battery Technology for New Energy Passenger Cars

It is suggested that domestic vehicle production companies should have a strategic layout. You can consider adopting a 1:1:1 power battery supplier selection mechanism. You can not allow a certain battery manufacturer to be dominant, otherwise you will have no bargaining power.

I think the domestic power cell market madness will continue in the short term. In the long run, this kind of "rush" investment expansion model, but also hidden the crisis of overcapacity! Will certainly repeat the mistakes of the photovoltaic industry that year!

Demand and supply of power cells will reach temporary balance in 2016

Since 2016, many battery companies have increased their production capacity and expanded their scale. According to the current development trend of new energy vehicles in the domestic market, the emergence of oversupply is a high-probability event. Supply and demand for power cells will reach a brief equilibrium in 2016.

On the one hand, better power cell manufacturers will continue to release their output due to increased investment; On the other hand, new energy vehicles will enter a period of calm after a year or so of explosive market growth. At the same time, in the rapidly growing market will also fully expose the problems existing in the new energy vehicles, the market competition under the phenomenon of survival of the fittest, some brands will be eliminated. It will also ease the supply and demand for power cells in new energy vehicles.

For the domestic power battery industry, in addition to the need to prevent overcapacity, there are also some bottlenecks in technology, safety and other technologies need to break through. If we can not achieve technological innovation and breakthroughs, the development of the Chinese power battery industry will only be a huge amount of production capacity, excess production capacity, not superior production capacity!

In particular, government subsidy policies should encourage people to use more new energy vehicles, that is, subsidize operations, such as subsidizing users in installments. Instead of subsidizing new energy car manufacturers, mass production of electric vehicles that do not meet market requirements.

The subsidy policy itself is a catalyst for the development of new energy vehicles. The state and local governments are in full play, allowing consumers to purchase new energy vehicles for double benefits, which can effectively promote the sales of new energy vehicles. However, we should note that any industry, especially the new energy automotive industry, can not be developed by government subsidies for a long time!

The new energy subsidy policy has virtually killed the enthusiasm of car companies in research and development. Change the shell and add a battery to the market to sell and enjoy the policy dividend. Companies that could have gone to the ground for basic innovation have had to stay focused on the current market. After all, it is far better to fight for a future than to fight for iron.

In addition, electric vehicles as a new category, its production chain is also very different from traditional cars, with a unique and complete design and production system. For traditional car companies, the introduction of a new production model means capital evaporation, which also affects the traditional car companies to find a breakthrough in the field of electric vehicles.

Whether or not the promotion of electric vehicles can be successful, it is crucial to improve the performance of infrastructure construction, operating cost control, lightweight body structure, energy-saving motors and batteries in the early stages.

I personally believe that the promotion of the commercial model of electric vehicles is the key, according to different business models need to carry out a targeted design of the power cell characteristics, in order to give a correct evaluation of different technical routes.

The page contains the contents of the machine translation.