At Tesla’s Battery Day event last month, Tesla CEO Musk unveiled a new power battery and released a new 4680 battery without poles. Low cost, fast charging, and long battery life, this battery is simply amazing! Recently, Musk revealed that the upcoming Model Y will be the first to use the 4680 battery, which has made the topic of this battery a hot search topic. Now it seems that it is very necessary to conduct a more in-depth analysis and discussion on the 4680 battery.
Maybe you will find it a bit boring, the prediction of the charging curve, the superimposed comparison of the packaging sizes of 2170 batteries and 4680 batteries, the configuration of series and parallel batteries, and the way Tesla connects batteries... But these contents will reveal to us a new car that is about to be launched and what kind of effects it can bring to us.
Is 4680 battery safer? Tesla’s 8-year-old battery cooling defect will be improved
Some foreign media commented that Tesla’s new 4680 battery pack will use a simpler and easier-to-assemble flat-plate cooling solution, abandoning the original There are cooling solutions. Although Tesla officials did not specifically emphasize that they will use a flat-panel cooling solution, because there is no way to effectively cool these larger-diameter batteries through the sides. The most efficient way to cool is through the ends of the battery, and the new earless batteries provide a good heat conduction path between the battery cover and the interior of the battery.
Regarding Tesla’s battery cooling defects, it was made public on June 30 this year after an internal Tesla email was exposed. As early as when Model S was mass-produced in 2012, Tesla already knew that there was a problem with battery cooling, which could even cause a fire. However, this problem has not yet been solved, and it has been eight years!
Tesla has commissioned three companies to test and investigate the battery cooling configuration, and the results all showed that there was a problem with the end connection accessories of the Model S cooling system. Tesla's battery cooling system is implemented by adding external coolant pipes to the battery. However, the end joints of the pipes use low-strength aluminum, which is easy to wear and crack, causing coolant leakage, causing the car battery to short-circuit and catch fire, or cause a fire in the car battery. Flammable residue is left inside the battery.
The copper anode electrode plate itself can play a very good role in heat dissipation, allowing the temperature to be more evenly distributed inside the battery. It seems that the eight-year-old safety hazard will be solved!
In addition, Musk said: The battery sheets are glued to the bottom and top plates of the battery pack. While increasing the shear strength of the battery pack, the top and bottom plates will also double as cooling plates. . In the Model 3 battery pack, the batteries are glued to the cooling plate.
How fast does the 4680 battery charge? It takes 15 minutes for 10%-80% and 7 minutes for 10%-50%.
Maximum charging speed: 275 kilowatts
The following is a comparative analysis of the 2170 battery pack and 4680 battery pack of Model 3 and Model Y.
When charging the 4680 battery pack at a temperature of 29.4 degrees Celsius (85 degrees Fahrenheit), the charging time from 10% to 80% was reduced from 25 minutes to 15 minutes. If you only need to charge to 50% of the battery, you can do it in 7 minutes, which is almost as fast as refueling a gasoline car.
The maximum charging rate is expected to increase from 250 kW for the 2170 battery to 275 kW for the 4680 battery. The charging rate of 275 kilowatts remains unchanged, with the charging rate gradually decreasing from 10% to 50% state of charge. The gradient begins when the battery reaches its temperature limit. According to Model? At higher ambient temperatures, the performance of your air conditioning system decreases.
The following is a comparison chart of the charging curve and time of the 2170 battery and the 4680 battery.
The following is a comparison chart of the relationship between the charging curves of the 2170 battery and the 4680 battery and the state of charge (SOC).
We can see that the size of the battery pack has been significantly reduced, and Tesla can pack the batteries more tightly after changing the cooling method.
This is an advantage because it reduces the polar moment of inertia and improves the vehicle's handling because mass is concentrated more in the center of the vehicle.
The following is a cross-sectional view of the 96S9P 76kWh 4680 battery pack.
A cross-section of a 4680 battery pack showing the top and bottom plate cooling and electrical connections to the cells. Tesla may cancel the concept of finger collectors and use wire welding and other methods, instead using simple plate collectors, which are directly welded to the battery body without anode or cathode connections.
In order to connect the anode of one group of batteries to the cathode of another group of batteries, the inversion technology based on Model S was re-used, that is, the batteries of each parallel battery group were flipped over. come over.
The following is a cross-sectional overlay of the 76 kWh 4680 battery pack and the 2170 Model? 3 battery pack.
As mentioned before, there is expected to be a top cooling plate and a bottom cooling plate, with the battery and cooling plates glued between them. The cooling plate will also add strength to the battery pack, with a 30%/70% heat transfer ratio between the cathode (aluminum) and anode (copper) ends of the battery.
The thermoelectric model includes all the specifics of the battery pack, including cell size, amp-hour rating, thermal conductivity, and more. One of the key factors is the battery's resistance, as this determines how much heat the battery generates. The new 4680 tipless battery has an initial internal resistance of 3 milliohms at 10% SOC and gradually decreases to 2 milliohms at 80% SOC. The resistance of the 2170 battery is 23/20/20? milliohms. We can see that the resistance of the battery is reduced by a factor of 10. In comparison, the technology marked in Tesla's patent application can achieve a reduction of 5-20 times.
In addition, the cooling capacity is also worthy of attention. The existing Model 3 cooling capacity is 2-3 tons, which depends on the ambient temperature. ?Tesla will likely increase the size of the stack refrigeration and AC compressors to provide better package cooling.
The thermal mass of the battery pack also comes into play. During the first part of charging at maximum charge rate, the battery generates more heat than the cooling system can keep up, so the battery pack starts to heat up. Thermal mass delays the onset of battery overheating because it stores heat. When the battery reaches its temperature limit of 45 degrees Celsius (113 degrees Fahrenheit), the charging rate begins to gradually decrease.
The above picture shows the relationship between A/C performance and ambient temperature. At higher ambient temperatures, air conditioning performance decreases, which is why the initial gradient point of maximum charging power occurs at lower SOC at higher ambient temperatures.
Dr. Zhang Ningxin (Secretary-General of Austria-China Science and Technology Exchange Association, working at a famous European technology institute)
The innovation of Tesla battery mainly comes from the innovation of peripheral non-core structure. For example, by increasing the size of the battery cell, the proportion of the casing is relatively reduced. The real improvement in energy density must and can only be achieved through material innovation. Innovations in production processes can reduce costs but have little impact on energy density. Innovation in battery positive and negative electrode materials will bring about a leap in the performance of lithium battery electrochemical systems, but this requires a long period of scientific research accumulation.
Engineer Jin Min (battery expert, working for a world-renowned automotive technology company, member of the Austrian Chinese Automotive Engineers Association)
The design of Tesla’s battery cell negative electrode is quite novel and traditional The internal resistance of cylindrical cells is higher than that of square cases and soft packs, about 20mΩ per unit. This new design can reduce it to less than 10, so that much less energy is consumed on the internal resistance of the battery.
The cross-section design of the battery pack removes the module and directs CTP (Cell To Pack), which is similar to what has been recently promoted by several domestic companies. ?However, looking at this cross-section, I am a little worried about the battery pack’s ability to resist extrusion and collision. The original internal reinforced upper and lower support structures are gone.
There are no specific investigation reasons and data. There are no Chinese companies and institutions in the above list. It can only be said that we need more efforts.
Wang Jun (senior engineer of a well-known European automotive technology company, president of the Austrian Association of Chinese Automotive Industry Engineers? ACSAE?) Top 25 battery technology patent registrations in the world from 2000 to 2018
Despite its advances in batteries, Tesla is considered a pioneer in electric vehicles.
?But the company doesn't even appear in the rankings for most patents in battery technology.
I have some views to share regarding battery recycling. From January to December 2019, my country's power battery production totaled 85.4GWh, a cumulative year-on-year increase of 21.0%. Battery recycling can certainly reduce the cost of new batteries. As far as the current development of the domestic automobile industry is concerned, NIO has started a business model of leasing batteries for electric vehicles, which provides a more centralized management of battery production, maintenance and recycling, and provides better conditions for battery recycling and reuse. conditions, I am very optimistic that the cost of automotive power batteries will continue to decrease rapidly.
Dr. Wang Yongli (ceramic battery material expert, working for the European branch of a world-renowned electronic raw material component company, member of the Austrian Chinese Automotive Engineers Association)
The recycling and reuse of battery raw materials requires very professional knowledge, skills and equipment, including a complete industrial system. Simply put, separating and regenerating the raw materials for battery production from old batteries may not be cheaper than refining new raw materials from ores under current conditions, so this is not only an opportunity, but also a challenge.
Of course, the recycling of old battery materials is of great significance from the perspective of sustainable development and environmental protection.
Tesla has begun to lay out the recycling and reuse of electrode materials, hoping to significantly reduce costs through localization and raw material selection (ranked third). Especially for cobalt materials, as a relatively expensive transition metal, my country's cobalt resource reserves only account for 1% of the global total. Therefore, cobalt resources are very scarce. The amount of self-produced ore cobalt metal is only about 1,500 tons per year, and the import dependence is 90 % or more, Tesla’s concepts in the development and manufacturing of electrode materials are worthy of reference and consideration by our battery industry.
This article comes from the author of Autohome Chejiahao and does not represent the views and positions of Autohome.