Pengpai News reporter Senning
How difficult is the 4680 battery pack of Tesla ? It took the dismantling team two weeks to remove the upper cover from the battery pack.
Starting from early July, the team of Munro Associates, a professional dismantling company in the United States, began to dismantle the 4680 battery pack loaded on the Tesla Model Y, but encountered unexpected difficulties and the work progressed extremely slowly. Last week, the team finally removed the battery pack and uncovered all the secrets of the 4680 battery pack.
According to the autorevolution website, the latest discovery was that the team originally believed that the entire 4680 battery pack did not contain fasteners, but in the end they still found 16 small threaded fasteners in the 4680 battery pack . Team leader Sandy Munro said that too many fasteners are prone to assembly errors, so it is a good thing that Tesla eliminates this weakness.
In September 2020, Tesla launched the "epoch-making" 4680 cylindrical battery. Tesla said that compared with the traditional 2170 cylindrical battery, the 4680 battery has a larger volume (diameter 46mm and height 80mm), and uses poleless ear (i.e., full-pole ear) and dry battery electrode technology, so that the energy will be 5 times that of the former, the vehicle's range will be increased by 16%, and the power will be increased by 6 times.
In April this year, the first batch of Tesla Model Ys loaded with 4680 battery packs were delivered. To the outside world, the structure of the 4680 battery pack is still quite mysterious.
According to reports, Sandy Monroe is a former engineer at Ford Motor Company. In 2018, he and his colleagues bought and dismantled two Tesla Model 3s at their own expense, and also gave Musk a lot of suggestions on the body design of Model 3. At present, the team has dismantled hundreds of cars from car companies such as Audi , BMW , Chevrolet , Jaguar , Nissan , and Tesla's Model S, Model 3, and Model Y (2170 battery version) have not been spared.
When the complete 4680 battery pack was removed, Sandy Monroe claimed that the structure of the 4680 battery pack is unprecedented. Compared with Tesla's previous 2170 battery pack loaded on Model Y/3, "it doesn't look like it was produced by the same company." In this disassembly project, the team first removed the 4680 battery pack from the Model Y body. They found that the battery pack and seat integration was very high, and the owner was almost driving on the battery. Parts such as the seat and central armrests are directly installed on the upper cover of the battery chassis, and only a few cross beams are spaced between the seat and the battery pack.
battery pack is connected to the body through 38 fixing bolts . Remove these fixing bolts and disconnect the wiring harness, the battery pack, the front main and co-driver seats, the central armrest box and other parts can be completely removed from the body through the elevator.
, and the entire 4680 version Model Y battery pack + front seat assembly + rear PSC high and low voltage control module weighs only 1198 pounds (about 543 kg). The total weight of the Tesla Model Y 4680 battery pack with the seat removed is less than 500 kg. Considering that the total energy of the battery pack is about 80kwh, the ratio of weight to energy is surprising. The step of
is easy, but then the team encountered big trouble. A member of the team said, "Removing the battery is like being archaeological."
They took a full two weeks to remove the lid of the 4680 battery pack. The team originally thought they would see rows of battery cells directly, but they were surprised to find that the battery cells and other key components were swallowed up by a pink foam that was "hard as bricks."
These pink foams are actually polyurethane glue. The team found that the 4680 battery pack uses glue filling to fix the battery cells and parts. This pink glue is used very much, not only filling the surface, but also filling the internal space of the battery cell completely.
According to reports, glue plays two main functions: one is to be subjected to force and protection. glue integrates all battery cells and parts into a whole, and is subjected to force together. The glue is elastic, which can absorb energy and thus protect the battery cell; the other is to fix the battery cell. Since the 4680 battery cell is cylindrical, there are many gaps between the battery cells. The battery pack saves traditional modules and has more gaps between the battery cells. Gluing can fill these gaps to prevent the position of the battery cell from loosening.However, these pink glues have a high viscosity, so it is quite troublesome to disassemble them. Musandi's team thought of using dry ice to remove the glue.
A week later, Sandy and his team used a dry ice jet to remove polyurethane foam and saw the battery cell arrangement structure inside for the first time.
The uppermost part of the battery pack is a flexible nylon cover plate, which is a honeycomb structure, and a wiring harness of voltage sampling and temperature sensor are integrated on it. The layer below
is a current collector connecting the battery cell into a series and parallel connection. Between the battery cell and the current collector, unlike the aluminum wire bonding welding used in the previous 2170 battery pack, the 4680 battery is selected for laser welding, eliminating the problem that the current collector may fail due to wire connections. The 9 battery cells are connected in parallel into a group, and the positive electrodes of each battery cell are connected together and then summarized to the negative electrodes of the next battery cell. Due to the design of the 4680 battery, only the pole pillar is a positive electrode, and the surface shell below the pole pillar is all negative electrodes, so the current collector is designed in the shape of a tree branch.
Note the small copper sheets on these solder joints. According to reports, this is the VSH (voltage sensor wiring harness) solder joints, connecting the battery cell and the battery management circuit board, which can monitor the voltage and temperature of each battery cell.
The next layer is the battery cell. The entire 4680 structure battery pack includes a total of 828 battery cells, divided into four areas by three partitions. The partition material is phenolic resin or high-density polyethylene . According to Tesla's previous introduction, the 4680 battery pack completely canceled the traditional module, but in fact, Tesla only canceled the traditional physical partition. This design is completely beyond Sandy's expectations. He believes that "the advantage of this design is to reduce the chance of thermal runaway." In terms of heat dissipation, the 4680 battery pack uses a snake-shaped cooling plate. The cooling plate passes through the middle gap between the two rows of battery cells, and adheres to the cylinders of the battery cells on both sides. The cooling plate has small pipes for cooling liquid to flow through, similar to the cooling circuit scheme of Model S plaid and ModelModeY. But in the 4680 battery pack, the cooling pipeline is thicker depending on the larger size and weight of the battery cell. There are partitions made of polystyrene material between each row of battery cells, which plays a good insulating role.
Then, what surprised the team members was that the bottom of the battery cell was not directly fixed to the chassis, but was embedded on black ABS plastic bases. Tesla also added a layer of mica board between the bottom of the battery cell and the base of the honeycomb to act as an insulating function. In addition, team members are expecting more structural connections at the bottom of the battery pack, including the water-cooled plate at the bottom, but in fact, there is only the exhaust line at the bottom.
team member Cory Steuben introduced, "If there is an overcharge problem, the entire body is exhausted downward."
On the side of the battery pack, the team saw four BMS battery management systems circuit boards sealed and protected by polypropylene plastic parts. On the previous Tesla Model Y/S, BMS was located at the bottom of the battery pack. The electrical part of the entire battery pack is pressed against the orange plastic board, and the communication line connects to the BMS through the top pipe.
After disassembling the entire 4680 battery pack, the question is, can such a battery pack be repaired? In Corey Stoybn's view, from the perspective of glue filling technology, the possibility of repairing a CTC battery pack (Cell to Chassis) such as Tesla is almost zero. Because repair involves complex processes such as glue coating, re-filling, sealing and waterproof testing, it is not cost-effective in terms of cost.
The structure of the entire battery pack also puts strict requirements on the process stability and production efficiency of battery manufacturers. This may explain to some extent why the 4680 battery has not been mass-produced on a large scale after it was released in September 2020. It is understood that the 4680 battery pack is currently only produced in small batches by Tesla's Kato Road factory in , California, and , Texas factory in , Texas . South Korea's LG New Energy and Japan's Panasonic both said that mass production will be until next year.
The last question - Can the 4680 battery pack be recycled? Sandy's team believes that although Tesla does not seem to have the possibility of repairing the 4680 battery pack, this does not affect the recycling of the 4680 battery pack.
The idea was confirmed by Elon Musk .
"There is no problem in recycling the 4680 battery pack," Musk wrote on Twitter after watching Sandy's live video, "Just think of any battery pack as a super high-level ore - starting with a high-level ore is better than starting with a low-level ore!" How to operate
? Sandy proposed the idea to throw the entire battery pack directly into the liquid nitrogen near absolute zero. "The battery pack will freeze, and then grind it into very fine debris through the grinder . Materials of different densities will float in the liquid nitrogen, so that all the substances in the battery pack can be recycled," Sandy said. "Just like mining, just choose the right machine and equipment."
Editor: Kang Yimei
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