Through patent documents, why does Tesla dare to let car owners drive on 4680 batteries?
Latest update time：2022-02-14 14:21
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What technological innovations does Tesla’s 4680 battery, which will be mass-produced in the first quarter of this year, have?
Recently, a report released by InsideEVs, a well-known overseas electric vehicle media, answered these questions.
The media's reporter George Bower (who has a background in mechanical engineering) conducted an in-depth analysis of the soon-to-be-produced 4680 battery pack and the supporting CTC technology (battery cells directly installed on the chassis) based on newly exposed Tesla battery patent documents and actual photos of the two new factories in Berlin and Texas. The analysis involved multiple aspects such as battery cell packaging process, battery pack structural design, thermal runaway management, and heat dissipation.
From its analysis, the combination of 4680+CTC does have many unconventional operations:
For example, the bottom of the Model Y equipped with a 4680 battery pack is hollowed out - the battery pack serves as the floor of the vehicle, and even the vehicle's seats are directly mounted on the outer shell of the battery pack.
The 4680 battery pack acts as the "chassis" of the vehicle body, which can reduce the number of vehicle body parts, lower costs and weight. However, it will also bring new challenges to the rigidity and safety of the vehicle body.
This approach is not only different from the vast majority of electric vehicles currently using a load-bearing body design, but also different from other CTC technologies that stuff battery cells into the chassis.
To give an example, others put battery cells into the chassis of the car body, while Tesla puts the "chassis" into the car body.
For example, the 4680 battery pack is filled with 4680 cells, but there is no obvious gap around it to serve as a collision buffer...
On the contrary, Tesla has set up a honeycomb hollow layer at the bottom of the 4680 battery pack, which seems to be to deal with the gas generated when the battery cell has thermal runaway and to provide a buffer when a collision occurs at the bottom.
In addition, it was found in the patent documents that the 4680 battery pack also uses a new welding process and a more comprehensive thermal runaway management design.
Although it is still unclear how much the 4680+CTC technology can improve the battery life of the Model Y, it is also unknown how Tesla's unconventional operations will solve the problems it brings - such as how to ensure the rigidity of the vehicle body and collision safety.
But these patents and photos all show that Tesla is indeed constantly iterating its battery design, and even making great strides in iterating.
As the number one player in the electric vehicle industry and the pioneer and leader of smart electric vehicles, Tesla's iteration and progress in battery technology is clearly worth watching.
CTC technology shows the true appearance of the seat, which is actually installed on the battery pack shell
Tesla also exhibited photos of the 4680 battery pack and the 2170 battery pack being installed in the vehicle. The 4680 battery cell is the latest technology, so George Bower conducted an analysis based on the photos and patents displayed by Tesla.
Judging from the photos of the 4680 battery pack that Tesla previously displayed, there are many things worth noting.
First of all, the 4680 battery pack directly cancels the module. Judging from the public photos, the 4680 battery cells are densely arranged in the vehicle chassis, canceling the module design in the previous battery pack, the so-called CTC technology.
▲Photo of Tesla's 4680 battery pack
After adopting this technology, the assembly process of the vehicle has also changed. George Bower discovered through the battery structure and paint color in the photo that the vehicle's seats are directly installed on the battery pack shell, which can also be seen from the reserved interface above the picture.
All previous media reports have also stated that after adopting the 4680 battery pack, the vehicle's seats will be directly installed on the battery pack casing.
In addition, the 4680 battery pack continues to use two heat dissipation pipes to better disperse the heat. In winter, it can also heat the battery cells more evenly.
After carefully looking at the photos, George Bower also found a problem. Tesla's 4680 battery cells are laid directly inside the vehicle's chassis. From the pictures, it seems that Tesla did not leave a certain space around the battery cells.
Generally speaking, car companies will leave a certain amount of space around the battery pack. On the one hand, this is to leave room for buffering in the event of a vehicle collision and to protect the safety of the battery cells. On the other hand, this is to deal with situations where abnormalities in the battery cells may cause gas generation.
In addition to the photos, George Bower also referred to the power battery patent previously applied by Tesla. The patent numbered WO 2021/102340 A1 published by Tesla on May 27, 2021 also shows the Model Y's 4680 battery pack.
▲Screenshot of Tesla patent
Patent images show that after adopting the 4680 battery cells, the vehicle's seats will be directly installed on the battery pack shell, and the battery cells will be laid directly flat inside the battery pack, no longer using the previous four-module design.
▲Screenshot of Tesla battery patent
At the bottom layer of the battery pack, George Bower discovered that Tesla designed an integrated honeycomb network. He speculated that this design could absorb the gases produced by the battery cells and also absorb physical impact in the event of a collision.
At the same time, he also believes that the structure will be a complete casting that can also serve as a structural member to improve the overall rigidity of the battery pack. Although this structure cannot be seen in the photos released by Tesla, George Bower believes that this structure will appear in mass-produced products.
▲Screenshot of Tesla battery patent
According to Musk's statement in Tesla's 2021 financial report conference, the 4680 battery pack will be mass-produced in the Austin plant first, and this information has been verified recently. George Bower found that the chassis of the Model Y manufactured in Tesla's Austin plant is blank, which seems to be prepared for the 4680 battery pack and CTC solution.
▲Photo of the car body at Tesla's Austin factory
According to the currently known information, the 4680 battery pack will adopt the CTC packaging method, the vehicle's seats will be directly installed on the battery pack shell, and there will be two heat dissipation pipes inside the battery for heat dissipation.
However, since Tesla has not yet officially mass-produced models equipped with the 4680 battery pack, there are still many uncertainties about the Tesla 4680 battery pack, such as whether the final mass-produced product will be exactly the same as what is shown in the patent, and other issues such as battery safety are also still unclear.
New honeycomb welding process improves thermal runaway management
In addition to these, Tesla also disclosed a patent on power batteries in June 2021, "INTEGRATED ENERGY STORAGE SYSTEM (patent number US 2021/0159567 A1)". From this patent, we can also see more information about the 4680 battery pack and CTC technology.
In terms of battery cell assembly, due to the increase in current of the 4680 battery cell, the aluminum wire connection method previously used by Tesla is no longer applicable. Instead, it is changed to a welding method called Busbar to connect the battery cells. At the same time, the acquisition board of the battery management system is directly connected together to reduce the use of wiring harnesses in the battery pack and reduce costs.
Filling resin materials are used above and below the battery cells and between the battery cells to provide thermal protection and structural support. The patent shows that resin materials can usually be appropriately adjusted within the limits of chemical substances, fillers and process requirements. Therefore, technicians can configure resin materials based on one or more considerations of heat resistance and flame retardancy, tensile modulus, elongation, yield strength, adhesive shear strength, mixed viscosity, processing time and density.
▲ Tesla battery cells will be filled with resin materials
This feature also provides flexibility in the battery array approach. Depending on product requirements, the cells can be partially or fully filled between the cells, and the resin layers above and below the cells can be directly bonded to the skin.
Tesla has also done a lot of work in thermal runaway management. Previously, the battery pack only had two pressure relief valves behind the battery. After adopting the CTC solution, the company faced more challenges in thermal runaway management.
It can be seen from the patent and the photos released by Tesla that Tesla has equipped eight pressure relief valves on one side of the CTC solution battery pack, almost covering the side of the battery pack. The advantage of this is that once thermal runaway occurs, the pressure relief valve can be opened quickly to reduce the risk of battery fire.
In terms of liquid cooling, the serpentine tubes in the CTC battery pack are arranged parallel to the direction of the axle, which can reduce the length of the serpentine tubes, thereby reducing flow resistance and increasing cooling uniformity.
It can be seen that Tesla has made a lot of preliminary preparations for the 4680 battery cell and CTC technology. Judging from the previously released photos, Tesla has moved the contents of the patent into reality. There is no doubt that Tesla is launching a new round of battery revolution.
2170 battery fine-tuning Model Y range increased by over 20km
In addition to the 4680 battery pack, the 2170 battery pack also appeared in the photos officially exhibited by Tesla. Although the Tesla Model Y currently uses the 2170 battery pack, a closer look reveals that the latest 2170 battery pack on display also has some changes.
After carefully studying the official photos, George Bower found that Tesla's latest 2170 battery pack adopts a large module solution. It can be clearly seen in the photos that the 2170 battery cells are composed of four modules, which together form a battery pack, which is very similar to the packaging method of the current Model Y battery pack.
▲Tesla 2170 battery picture
Unlike the 4680 battery pack, the models using the 2170 battery pack do not have the solution of directly installing the seats on the battery pack shell. The picture clearly shows that the bottom plate of the car body is above the upper shell of the battery, and there are seat installation holes on the bottom plate crossbeam.
Even the paint scheme shows that the vehicle seats are not mounted on the battery pack housing; the floor and seat supports above the battery pack are painted white, the same color as the body, whereas in the 4680 battery pack, the seat supports are painted black, the same as the battery pack.
However, Tesla's latest 2170 battery pack and 4680 battery pack also have certain similarities. Both battery packs do not have obvious excess space to absorb the kinetic energy of the impact and the abnormal release of gas from the battery cells.
The 2170 battery pack was also mentioned in the patent with serial number WO 2021/102340 A1 published by Tesla on May 27, 2021. Some pictures in the patent also prove George Bower's speculation.
▲Screenshot of Tesla patent
Judging from the patent images, Tesla's latest 2170 battery pack still uses a four-module solution, which is basically the same as the currently sold Model Y. The lengths of these four modules are not the same, the lengths of the two modules in the middle are relatively close, and the lengths of the modules on both sides are also relatively close, but overall, the lengths of the two modules in the middle are longer.
▲Screenshot of Tesla patent
In addition, the patent images show that the seats of the Model Y, which uses the new 2170 battery, are directly connected to the body of the car, and not directly connected to the battery pack.
▲Screenshot of Tesla patent
At the bottom of the battery pack, there is also an integrated honeycomb network reserved to absorb the kinetic energy of the impact and abnormally released gases, but it is currently impossible to confirm whether this component is die-cast in one piece.
▲Screenshot of Tesla patent
According to previous information, Tesla's Berlin factory will still use the 2170 battery pack in the early stage. The long-range version of Model Y produced by the factory has a range increased from 537 kilometers to 565 kilometers compared to the domestic version.
Conclusion: 4680+CTC will be Tesla's future focus
Battery technology and autonomous driving technology are undoubtedly Tesla’s two most anticipated technologies at present, and the battery technology that is about to be put into production is even more worthy of attention.
Judging from the photos and earnings conference calls released by Tesla itself, both the 4680 battery pack and the 2170 battery pack will become Tesla's next major battery products.
Tesla's ultimate goal is to invest in 4680 battery packs and CTC technology on a large scale. At present, the output of 4680 battery packs is still relatively small. Whether Tesla produces it itself or purchases it from suppliers such as Panasonic and LGES, the Austin factory in the United States is geographically closer. In the European market, Tesla cannot obtain more 4680 battery packs in a short time, so it will temporarily use 2170 battery packs.
Despite this, the Berlin factory is also actively building a battery factory, and will replace it in the future when the production capacity is further released. Overall, 4680+CTC will be the main development direction of Tesla in the future.
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