Interpretation Tesla Model 3 battery technology and battery pack dismantling

As early as last year when Musk announced the battery pack used in the Model 3, we knew that Tesla used its latest battery matching technology, eliminated Matsushita 18650 battery, and switched to 21700 new battery, from Nevada. The state's "super battery factory" (Gigafactory) production.

The same type of cylindrical Lithium Battery, 21700 new battery specifications for the diameter of 21 mm, length 70 mm, on the theoretical upper limit than the 18650 type (diameter 18 mm, length 65 mm) is more favorable. For this reason, the 21700 lithium battery was first used in Model 3.

1.21700 battery advantages

In terms of advantages, the 21700 is mainly improved in terms of energy density, cost, and weight in comparison with the 18650. These three enhancements make the Model 3 sound more “comfortable”. Let's analyze it little by little:

1) Increase energy density by more than 20%

The 21700 battery has a better energy density than the 18650 battery. From the information disclosed by Tesla, under the existing conditions, the energy density of the 21700 battery system it produces is around 300Wh/kg, which is about 20% higher than the 250Wh/kg of its original 18650 battery system. From the test data of Panasonic's power lithium battery, the volume energy density of its 21700 battery is much higher than that of the 18650 battery cell. The increase in the energy density of the single cells is much higher than the increase of 20% after the group.

2) Battery system cost drops by about 9%

Lithium Battery Data According to the battery price information disclosed by Tesla, the price of the 21700 power lithium battery system is expected to be US$170/KWh, which is about 8.1% lower than the price of 18650, US$185/KWh. The cost of the 18650 system is approximately $171/kWh. After switching to 21700, the system cost can be reduced by about 9% to $155/kWh.

After the capacity of the monomer is increased, the number of accessories required for PACK decreases as the proportion of PACK decreases. After switching from the 18650 model to the 21700 model, the battery cell capacity can reach 3~4.8Ah, a significant increase of 35%, the number of required batteries can be reduced by about 1/3 for the same energy, and Tesla Models electric cars use 7104 18650 batteries. Series and parallel connected into a battery pack, in the new Models 3, using the 21700, the battery number will be significantly reduced. While reducing the difficulty of system management, while reducing the number of metal structural parts and conductive connectors used in the same proportion of reduced battery packs, Tesla's Pack costs account for about 24% of the total system cost, and it is expected that the cost of battery packs will be considerably reduced.

It is worth mentioning that Tesla did not design the Model 3 battery as an easy-to-replace model. It seems that Tesla has completely abandoned the battery replacement program, which is also closely related to the cost.

3) Lighter weight reduction by 10%

With the new 21700 battery, the system can reduce the components and weight by 10% compared to the current battery, thereby further reducing the weight of the battery pack, and the overall vehicle energy density will be partially improved.

Model 3 has a total of four configurations, namely: 50, 65, 80, and P80D. The number corresponds to the total capacity of the loaded battery. The battery capacity corresponds to different cruising range (EPA test): 357 km, 454 km, 550 km, and 539 km. However, as regards the service quality, it is 1,650kg, 1,725kg, 1800kg, and 1,925kg, respectively. As an overall size (4694/1849/1443mm) and BMW 3 Series (1540kg ~ 1650kg) equivalent, or a lot of weight.

In addition, Tesla has added some other clever designs to save on weight and cost. For example, it removes the external battery pack heater and uses only the heat provided by the car's powertrain to heat the battery even if the car has stopped. This is because batteries need to work at a suitable temperature to maintain their optimum performance, which means that they need to be cooled in an overheated environment and heated in cold weather.

2.21700 Battery "Black Box"

The so-called "black box" refers to a device or product from the user's point of view, does not care about its internal structure and principle, but only concerned about its function and how to use these functions. Then we look at the 21700 from the user's point of view!

1) Does the downstream market accept change?

What type of battery a battery company produces depends on many factors. At present, the "positive research and development" emphasized by the new energy automotive industry requires that the design structure be started from the function. This also determines that the battery model and specification must be pushed backwards from the use. Therefore, whether or not the battery model is replaced mainly depends on the downstream market.

"The 18650 is highly adaptable. Apart from electric vehicles, it can also be digested in 3C digital, drones, power tools and other fields. But for 21700, there is no effective industrial chain to digest these batteries. This will undoubtedly increase costs."

2) Is the equipment and process satisfied?

21700 battery production equipment, production processes, etc. will not be ready one day, how to layout depends on the battery manufacturer's competitive strategy.

The cost reduction of the battery is based on yield and yield. SPIR data shows that the Panasonic and Samsung SDI's 18650 battery yields are generally above 98%, and domestic yields are generally above 95%, but this still means that there will be more B-cells to handle. This is a serious challenge for the 21700.

3) Does the policy support?

In addition to the lack of market demand and the lack of manufacturing processes for battery companies, the country's related policies on battery size standards also have a major impact on the choice of domestic battery sizes.

In the draft of the “Dimensional Specifications for Power Battery for Electric Vehicles” drafted by the Ministry of Industry and Information Technology, the recommended cylindrical battery models are only 18650 and 32650. Once forced to be unified, it will be detrimental to other types of batteries. If the country does not explicitly support the battery size standards, the development prospects of this type number will not look so good.

1. In addition to the battery, the vehicle's life is related to the operation under different conditions. Since the latter's problems are more complex, today we will mainly talk about batteries.

2. The most important performance parameter of a battery is the energy density. The energy density has a volume energy density (Wh/L) and a mass energy density (Wh/kg). What we talk more about on the battery is the mass energy density (Wh/kg), which determines the amount of energy stored in a unit of weight.

3, the battery's energy density often points to two different data, one is the battery system's energy density, one is the battery's energy density.

The Cell is the smallest unit of a battery system, and it is also described as a single cell. You understand it as a single battery, for example, a fifth battery. M cells form a module, and N modules form a battery pack. This is the basic structure of a vehicle power battery. Some people also call the battery pack directly a battery pack.

▲ The Nissan Leaf uses a soft pack battery. From top to bottom, batteries, battery modules, and battery packs are used.

In fact, it is a very simple formula, battery pack = N·module = N·(M·cell).

4. Since the battery pack relates to the final shape of the battery and the layout of the vehicle, most manufacturers will choose to purchase batteries and do their own battery system. The energy density of the battery system is related to the selection of the battery. For example, a cylindrical battery has a small capacity and a complex battery system structure. The energy density of a battery system is relatively low under the premise that the energy density of a single battery is dominant. (Conclusion refers to the report from McKinsey)

▲ Electric car manufacturer's battery supply chain strategy, original image from McKinsey, 42nd garage translation.

5, divided from the structure, there are three types of batteries, Prismatic battery, soft pack battery (Pouch) and cylindrical battery (Cylindrical).

▲ From left to right are cylindrical battery, square battery and soft battery.

Divided from raw materials, the batteries have different types of lithium iron phosphate, nickel cobalt manganese (NCM), and nickel-cobalt-aluminum (NCA). The materials here mainly refer to the cathode materials. In the influence of raw materials, the positive electrode material has a great influence on the energy density of the cell.

Anode materials are generally dominated by graphite. Currently, the mainstream research direction is to explore the commercialization of silicon-carbon anodes.

The structure of the cell and the composition of the raw materials have different effects on the energy density of the cell.

3. Battery pack capacity

Unlike the previous Model S and Model X, Tesla did not use conventional “kilowatt-hours” to represent its battery capacity when it released the Model 3, but only given a charging rate: 240V, 30A. In the case of charging, you can drive 30 miles per hour (about 48.28 kilometers).

Tesla battery pack

So, what is the battery capacity of the Model 3? According to previous EPA official certification information, the standard model Model 3 has a cruising range of 350 km, a battery capacity of 50 kWh, and uses 2976 21700 batteries, each of which constitutes a battery brick. These battery bricks are further divided into 4 modules, of which 2 sets contain 23 battery brick modules and 2 sets contain 25 battery brick modules.

Tesla battery layout diagram

The Model 3 long-range version has a cruising range of 500 kilometers, a battery capacity of 80.5 kWh, and uses 4,416 21,700 batteries. Each of the 46 batteries constitutes a battery brick. Like the standard Model 3, these battery bricks are divided into 4 modules.

4. Battery decay rate

Attenuation is inevitable for any rechargeable battery. With the increase in the number of charge cycles, the positive and negative electrode materials in the battery will be lost, and the performance of the electrolyte will also be reduced, resulting in the actual battery power reduction. In general, for example, a lithium-ion battery with a relatively chemical nature is used. After 500 charge cycles, the battery capacity is reduced to about 80%.

For Model S/X, Tesla never promised its battery health. However, Model 3 has official data, that is, after 200,000 kilometers, it can still maintain more than 70% capacity. But is it true that the Tesla official declares so ideal?

According to foreign media reports, a survey of hundreds of real owners of Tesla revealed that after driving 100,000 kilometers, the battery capacity of the Model S/X shrank by 5%, after 300,000 kilometers, the majority Sura can also guarantee more than 90% of the battery capacity, and after 800,000 kilometers, it can still maintain a level of more than 80%. And, frequent charge and discharge can even slow down the attenuation.

5. Model 3 battery pack dismantling

Recently, a foreign body dismantled the battery pack of the Model 3, and today we take a look at the dismantling situation.

Lift the car on the gantry

Analysis of the vehicle before removing the battery pack

Start to remove the battery pack

Battery pack removed

Analysis of the disassembly of the battery pack

Battery pack overall

In general, battery packs are flat and beautifully designed.

The white box on the right is DCDC

The middle silver-white piece is a high voltage distribution box

Battery module

The orange line is the high voltage line

Dismantling the high voltage line

Dismantling the battery box cover

Remove the battery module

Battery module close-up 1

Battery module close-up 2

Battery module close-up 3

The first battery module has been removed

Check the first battery module

Battery module connection method close-up

Disassembled battery module as a whole close-up

Battery module panorama

CMU connects Goldfinger and FPC with 3 Bonding lines

Battery module dismantling panorama

BMS motherboard

Disassemble the battery module

Dismantling ended

Model 3 is a new product of the Tesla Model X series. In July 2017, Tesla announced that the first 30 Model 3 models will be delivered to customers on July 28, 2017. However, as of May 28, 2018, the model was only delivered in the United States and Canada, and Tesla delayed the delivery of the Model 3 to Europe in 2019.

There is no doubt that Tesla is now under tremendous pressure, after all, the company has already reneged on it many times. In a recent interview with CBS, Musk talked about the pressures the company is currently facing: I am currently under pressure and things have become extremely difficult and annoying in the past few months. Yes, now I've been sleeping on the factory floor. It's not because it's fun to sleep there. It's too bad. For this reason, how do you see the happiness of Margot?

The Tesla plant in Fremont, California, is one of the world's most advanced automotive plants. It has a 5.3-million-square-foot production and office area and covers a total area of approximately 370 acres. With the approval of Tesla’s expansion plan in Fremont, the company’s plant will double in size to nearly 10 million square feet and create thousands of new jobs in the next few years.

Prior to Tesla, Fremont was affiliated with General Motors from 1962 to 1982; from 1984 to 2009, the plant was owned by Toyota's new United Motor Manufacturing Corporation (NUMMI). Tesla acquired the plant in 2010 and upgraded it. In June 2012, Tesla's first Model S was rolled out of the factory. In order to change the dim and closed environment of the factory, Tesla added a skylight to the factory, introduced natural light to the workers, and sprayed the ground with white epoxy resin to create a clean working environment. At the same time, the factory also set up cafeterias, gymnasiums, health centers and outdoor recreation areas.

In order to achieve its goal of ramping capacity to 500,000 cars in 2018, Tesla is working hard to build the world's most automated manufacturing system and ensures that most of its functions are rigorously trained to meet Tesla's production process. Up to now, the productivity of the Tesla Fremont has increased by 400%. After the Model 3 is put into production in 2017, this productivity will increase again. Every Model S, Model X, and Model 3 produced at the Fremont plant, as well as most parts of the vehicle, embody Tesla's highest level of production technology.

Tesla Factory Facility Map, Fremont, CA

In the Tesla workshop mentioned in this article, almost all production processes and work (except for a few parts) are self-sufficient in the assembly of raw materials into finished products. Therefore, it is called the world's most intelligent and fully automated. Production workshop.

In the four major manufacturing processes, namely stamping production lines, body centers, paint centers and assembly centers, it is conservatively estimated that more than 150 robots are involved in the work. You can hardly see people here.

All robot assembly centers

Robots that can complete many actions

Spray paint workshop list

The process of installing the windshield

The process of installing the seat

One engine cover stamping is completed in only 6 seconds

The process of finely processing the engine

Only one robot can handle the frame

Pipeline operation process machine people seamlessly docking