What is the reason for the new energy electric car selected 18650 lithium ion battery?

　　Author ：Iflowpower – Portable Power Station Supplier

18650 Battery is an early, mature, stable lithium-ion battery, widely used in electronic products. Over the years, Japanese manufacturers have accumulated a large number of related experiences in the processing technology of 18650 batteries, making the consistency of 18650 batteries, and the safety of high levels. In contrast, laminated lithium-ion batteries are far from mature, common with square batteries, soft bag batteries, even even dimensions, size, extreme ear positions, etc.

, the processing technology of battery manufacturers cannot meet the conditions Most of them are human-controlled, and the battery has no level of 18650 battery. If the battery consistency is not required, the management of a large number of batteries, and the management of the battery pack formed in parallel will not allow each battery to better play, and the 18650 battery can handle this problem. Summary, the monomer capacity of the 18650 battery is small, the number of monomers required will be much (Models has 7104), but the consistency is very good; the capacity of the stacked battery can be done large (20ah to 60ah), single The number of people can be lowered, but the consistency is poor.

In contrast, it is difficult to invest in a large number of human materials and battery suppliers to improve the processing technology of laminated batteries. Therefore, when R & D Roadster and Models are developed, Tesla's unique choice is to purchase batteries from the market, and develop battery systems. Developing a battery system for managing more than 6,000 units of consistent consistency and a battery system that has been more than 200 more than 200 more consistency, compared with the former's technical difficulty should be lower.

Even if the number of monomer batteries is increased, if the performance of these batteries is reliable, it is easy to manage. Compare another successful pure electric car, LEAF of Nissan, which uses a laminated lithium-ion battery. This is because Nissan and NEC cooperation for many years, accumulating in battery technology and has considerable skill in quality control.

Leaf's battery comes from AESC Nissan and NEC. Lithium-ion batteries produced comparison, daily, medium different regions of automakers in the development of electric vehicles, with battery manufacturers, the combination of battery manufacturers, is very interesting. The thickness of the heat dissipation capacity laminated battery is very thin, the surface is large, hot, and the heat dissipation ability is good.

Therefore, the daily LEAF has boldly adopted the passive thermal management system (in fact, not managing!), With the air of the natural pending heat away. From left to right, LEAF from the monomer, to four cell modules, two string of two strings, and then consisting of 48 battery modules, as shown below: It can be seen that there is no battery pack Any fan, cooling liquid pipe and other heat management system. Probably this is no victory.

In turn, Tesla, 18650 battery's head is relatively small, and the temperature difference between the monomer battery is not too large when normal charge and discharge. However, the temperature difference of more than 6,000 unit cells should also remain in the range of no more than 5c, this is a very difficult thing. However, Tesla did it.

How did you do it? Tesla's battery management system (BMS) What is the advantage of other electric cars? These pipes are the flow path of the coolant. The average distribution of the flow path is in the middle of the battery module. Each battery can be touched well, so that each of the cells taken away in cooling when cooling is almost the same, temperature difference It can also be effectively controlled within a small range.

Summary, due to the use of small capacity of 18650 batteries, Tesla's thermal management system has a great new increase. Also, if you consider the capacity of heat dissipation, use small capacity 18650 batteries is not excellent choice. About the energy density talks about energy density, non-distinguishing the energy density of the unit cell and the energy density of the battery pack.

In the energy density of the monomer battery, 18650 battery is higher than the laminated lithium ion battery. The energy density of the 33 AH lithium ion battery used by Nissan LEAF is 157WH / kg, and the energy density of the laminated battery used by GmVolt is about 150Wh / kg; and the energy density of the 18650 battery used by ROADSTER is about 211Wh / kg. However, the 18650 battery management system is more complicated, and thereby adding additional weight enables the energy density of the battery pack than the energy density of the monomer.

The capacity of RoadSter is 450kg, and the energy density is 118WH / kg, and the weight of the Leaf battery pack is 225kg, and the energy density is 107Wh / kg. At the battery pack, the energy density of the two is already up and down. There are also some shortcomings in front of the safety of the laminated lithium-ion battery, but it also has some shortcomings.

Since the laminated lithium ion battery is generally used in aluminum film packages, the thickness of the aluminum-plastic film is thin, the mechanical strength is poor, and the aluminum-plastic film is easily damaged by the automobile, and the aluminum-plastic film is easily damaged. This also explains why Nissan has to add a aluminum shell outside the battery module composed of 4 monomers. 18650 The battery is generally steel shell, more security; and mentioned above, as the 18650 battery process level is constantly improving, security is constantly improving.

Tesla also poured a lot of heart blood on the safety accidents that might appear in these 18650 batteries. If a single battery has a temperature over high abnormal situation, the battery or the module thereof will be powered down to spread the spread of alert accident based on the harshness of the abnormal conditions. Since the monomer capacity is small, as long as there is no spread, the severity of the accident will be lower.

About the cost 18650 lithium-ion battery has the characteristics of large capacity, long life, high safety performance, but also because of small size, light weight, convenient use, deeply loved by consumers. As people continue to deepen 18650 battery technology, the consistency and security of the battery have reached a very high level. As the early lithium-ion battery, 18650 battery is also currently a mature, stable battery in the world, still occupying priority.

my country's processing of 18650 batteries per year is about billion sections, far exceeding other materials. Tesla uses 18650 batteries, which can be processed using the processing lines before Japan Panasonic and other manufacturers. In the case where the 18650 battery competition used in the consumer electronics is increasingly violent, Panasonic cooperates with Tesla to upgrade the product, and the original processing line is improved and used for processing power lithium-ion batteries.

Industrial processing has a scale effect. After the scale of the processing product reaches a level, the cost will be greatly reduced. A new energy vehicle should make thousands of sections 18650 batteries, so the purchasing cost of the monomer is controllable.

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