China’s CITIC Securities recently published a 94-page research report on the Tesla Model 3, and it’s worth noting that they bought a specialSla Model 3, and then dismantle this car completely,It took two months to conduct a complete analysis of the Model 3 standard battery life.
Through dismantling, CITIC Securities conducted a detailed and in-depth analysis of Tesla’s E/E architecture, three power systems, thermal management, and bodywork.Here are the highlights from this report
Global Controller Architecture
The electrical architecture of traditional automobiles is distributed, and different functions correspond to different ECU architectures. However, with the intelligent upgrade of automobiles, there is a so-called Domain Control Unit, which integrates the functions that were originally isolated from each other. Several “central brains” are used to control the ECUs and sensors of the whole car, so that many ECU functions with similar but separate functions are built into a processor hardware platform that is more powerful than ECU functions. The proposal of domain controller makes the car intelligently upgraded The cost of research and development of automobiles is gradually reduced, making the implementation of automobile intelligence accelerated to become a reality.
Tesla’s E/E architecture has shifted from a distributed to a global control structure. The decoupling of software and hardware is the key to software-defined cars. Tesla’s Model 3 is the leader of the global control architecture.
1. In the body area, the front, left, and right three bodies are divided by position rather than function, which is intended to reduce the difficulty of wiring, and a large number of HSDs are used instead of relays.
The position of the front body domain controller is in the front cabin. In theory, the collision probability is higher in this position. Therefore, the aluminum alloy protective shell is used, and the left and right body domain controllers are in the passenger compartment and encounter external collisions. The probability is low, and the protective shell is made of plastic structure.
2. In the cockpit domain, the T-BOX is built into the cockpit domain controller, and Intel’s A3950 chip is used at the same time, the idea is closer to the game platform than the mobile phone
The cockpit domain is an important part of the user experience, and Tesla’s cockpit control platform is constantly evolving. The Tesla model 3 2020 dismantled by CITIC Securities uses the second-generation cockpit domain controller (MCU2).
MCU2 consists of two circuit boards, one is the motherboard, and the other is a small wireless communication circuit board fixed on the motherboard (indicated by the pink box in the figure). This communication circuit board includes LTE module, Ethernet control chip, antenna interface, etc., which is equivalent to the T-box used for external wireless communication in traditional automobiles. This time, it is built into the MCU, which can save space and cost . The 2020 model 3 we dismantled this time uses Telit’s LTE module. After the 2021 model, Tesla will switch the wireless module supplier to Quectel.
The main board of MCU2 adopts a double-sided PCB board, and the front side mainly lays out various network-related chips, such as Ethernet chips from Intel and Marvell, LTE modules from Telit, and video serializers from TI. Another important role of the front is to provide external interfaces, such as Bluetooth/WiFi/LTE antenna interface, lens input and output interface, audio interface, USB interface, Ethernet interface, etc.
The back of MCU2 is more important. Its core is an IntelAtomA3950 chip, with a total of 4GB of Micron memory and a 64GBeMMC storage chip also provided by Micron. In addition, there are WiFi/Bluetooth modules provided by LGInnotek.
3. Driving domain, dual FSD chips, NPU has higher cost performance than Orin in the same area, using Linux operating system is more suitable for AI large model
Another important feature of Tesla is its intelligent driving, which is performed through its Autopilot domain controller (AP). The core of this part is the FSD chip independently developed by Tesla, and the rest of the configuration is no different from other current autopilot controller solutions.
The HW3.0 version AP used in model3 is equipped with two FSD chips, each with 4 Samsung 2GB memory chips, a single FSD totaling 8GB, and each FSD is equipped with a Toshiba 32GB flash memory and a Spansion 64MB NOR flash for startup. On the network side, the AP controller includes Marvell’s Ethernet switch and physical layer transceiver, as well as TI’s high-speed CAN transceiver. For autonomous driving, positioning is also very important, so it is equipped with a Ublox GPS positioning module.
In order to achieve autonomous driving, Tesla has proposed a complete set of vision-based solutions centered on FSD chips:
“The peripheral sensors mainly include 12 ultrasonic sensors (Valeo), 8 lenses (3 front view on the windshield roof, 2 B-pillars for shooting side front, 2 rear view on the front fender, rear view 1 rear-view lens, and 1 DMS lens), 1 mmWave radar (Continental).”
Its core front-view trinocular lens includes the main lens in the middle and the telephoto lens and wide-angle lens on both sides, forming a combination of different fields of view. The three lenses use the same ON Semiconductor image sensor and millimeter wave radar. Placed near the car logo at the front of the car, including a circuit board and an antenna board. The millimeter-wave radar uses a Freescale control chip and a TI regulated power management chip.
4. In the electrical control domain, Model 3 is the first to use 48 SiC MOSFETs to replace 84 IGBTs, which greatly reduces the volume and power consumption;
According to CITIC Securities, Model 3 is the first pure electric vehicle to use a full SiC power module motor controller, creating a precedent for SiC applications.
The SiC model used in Model3 is ST GK026 from STMicroelectronics. At the same power level, this SiC module uses laser welding to connect the SiC MOSFET, the input busbar and the output three-phase copper. The package size is also significantly smaller than that of the silicon module, and the switching loss is reduced by 75%. By replacing IGBT modules with SiC modules, the system efficiency can be increased by about 5%, and the number of chips and the total area are also reduced. If Model X IGBTs are still used, 54-60 IGBTs are required.
5. In the power domain, BMS manages a total of 2976 21700 batteries, and the powerful software capability realizes the consistency of charging and discharging of each battery.
Model3 is an electric vehicle, the management of power and battery is very important, and the BMS responsible for managing the battery pack is a difficult product. The main control board is responsible for managing all BMS-related chips, and a total of 7 sets of external interfaces are set, including the charging controller ( CP), the control signal of the power conversion system (PCS), and the signal to the sampling board (BMB), in addition to the special current and voltage acquisition signal. The circuit board contains circuit modules such as high-voltage isolated power supply and sampling circuit. In terms of components, there are microcontrollers from Freescale and TI, as well as operational amplifiers, reference voltage sources, isolators, and data sampling chips.
Under the control of BMS, the battery pack is specifically monitored by the BMB circuit board. For Tesla model 3, there are 4 battery packs, each group is equipped with a BMB circuit board, and the circuit layouts of the 4 circuit boards are different. They are not the same, they can be easily distinguished from each other by the number on the circuit board, and they are connected together with a daisy chain in sequence, and the daisy chain is connected to the P5 and P6 interfaces of the main control board on the No. 1 and No. 4 boards. .
Harnesses and Connectors
1. Wiring harness, CITIC Securities estimates that the value of a single vehicle is about 2,000 yuan (RMB). High-voltage wiring harnesses are the main increment of new energy vehicles. Model 3 begins to use aluminum instead of copper for light weight. reduced.
2. Connectors, electrification brings the increase of high-voltage connectors, and intelligence brings demand for high-speed connectors. TE (Tyco) is the core supplier of Model 3, and domestic manufacturers are expected to make breakthroughs.
On the power battery-electric drive high-voltage wiring harness connector, Model 3 uses TE’s HC Stak 25, which is similar in structure and function to HC Stak 35. The difference lies in the size. It can be seen that HC Stak 25 is larger than HC Stak 25. The 35 is smaller, so the terminals on the socket end of the HC Stak 25 are composed of 20 pieces of DEFCON terminals (35 pieces for the HC Stak 35), and different models share the same connector terminals. The connector terminal can quickly complete the assembly of different models through the change of the number of stacks, which reflects the cost control advantage brought by the modular production of the connector.
Battery: Tesla’s intergenerational technology leads, 4680 and CTC are the follow-up development direction
1. The core concept of battery design is to improve specific energy, from small modules to large modules to no-module CTC, and the cell size from 1865 to 2170 to 4680. The core trend is to reduce non-energy structural components in battery packs Quantity, reduce cost, reduce weight, and increase cruising range. According to CITIC Securities, the Model 3 battery pack uses 4 large modules. Compared with the iD.4 X and BMW iX3 battery packs in the same period, it adopts large module technology, has a higher built-in degree, and has a cleaner internal layout. Technology is still leading the way.
2. The value and changes of the 4680 battery, the 4680 achieves the impossible triangle of “high energy density, high rate, and low cost” through the combination of all-pole tabs, high nickel and high silicon, dry electrodes, and CTC. As the number of batteries in the module increases and the demand for fast charging increases, the cooling, thermal conductivity and flame retardant requirements for battery packs increase. The number of cooling pipes in the battery pack increases, the length of the cooling pipes decreases, and potting and fireproof foam are added to ensure the battery pack. Thermal stability.
Three electricity and thermal management: The built-in degree of three electricity has been continuously improved, and thermal management has taken the lead in realizing global opening.
1. Three-in-one improves the built-in degree, and dual motors realize complementary advantages. The drive motor, motor controller, and gearbox on the Model 3/Y are integrated into one, and the built-in degree is higher than that of the Model S/X. ” and built-in battery pack, compact structure and lower cost; single motor version evolves from induction motor to permanent magnet motor, dual motor version evolves from forward induction motor and rear permanent magnet motor layout, and the two motors complement each other in high-speed and low-speed areas.
2. The whole area of thermal management is opened, which greatly improves the efficiency of energy utilization. In terms of thermal management, through the application of four-way valves and eight-way valves, the independent circuits of each part are used to upgrade the thermal management of the whole vehicle that is connected to the air conditioner, battery system, and power system. , the vehicle heat source is built-in to improve the energy utilization efficiency of the system. Tesla’s three-electricity and thermal management system maintains a leading position in terms of high built-in degree, and its demonstration role will lead the industry to catch up with upgrades and secondary innovations.
Auto body: Lightweight demand for integrated die-casting of aluminum body becomes a trend, consumption upgrades skylight glass and smart lights become the trend
1. The body is lightweight to meet the requirements of energy saving and improved battery life. It is the best choice to replace steel with aluminum, and the integrated die-casting of the rear body starts from Model Y.
2. Car lights, Model 3 exterior decoration has both a sense of technology and beauty, and the car lights use matrix LED light sources.
3. Automotive glass, Model 3 sky curtain leads the industry trend, and the penetration rate is expected to continue to increase.
4. Chassis, using wire-controlled chassis, is the only way for high-level automatic driving.
According to CITIC Securities, the Model 3 chassis is gradually being controlled by wire. After the dismantling of the Model 3 chassis structure, we can see: In terms of suspension, all Tesla models use the front wheel double wishbone independent suspension with the rear wheel multi-link. In terms of braking system, Tesla uses the most cutting-edge technology, that is, the brake-by-wire system Ibooster; in terms of steering system, Model 3 still uses traditional electric power steering.
The drive-by-wire chassis is the “execution” cornerstone for the realization of autonomous driving SAEL3. The automatic driving system is divided into four parts: perception, decision-making, control and execution. Among them, the chassis system belongs to the “execution” mechanism in automatic driving and is the core functional module for the ultimate realization of automatic driving. The realization of higher-level autonomous driving at L3 and above is inseparable from the rapid response and precise execution of the chassis actuator to achieve a high degree of coordination with the upper-level perception, decision-making and control. The upgrade of the chassis system also means the upgrade of functional modules such as the drive system, braking system and steering system. Therefore, the wire-controlled chassis, as the cornerstone of the execution of higher-level autonomous driving, is the specific starting point for the development of autonomous driving.
