Core ideas
The 800V architecture is the mainstream choice for all-class models to achieve fast charging. For the battery end, the fast enrichment is qualitatively to increase the charging current of each cell where the branch, and with the continuous introduction of bicycles with more than 100kWh of power, the number of cells increases, if the 400V bus voltage specification is still maintained, the number of cells in parallel increases, resulting in an increase in the bus current, which brings great challenges to copper wire specifications and thermal management.
Therefore, it is necessary to change the string parallel structure of the battery pack, reduce the parallel connection and increase the series connection, in order to increase the branch current while maintaining the bus current at a reasonable level. As the number of series is increased, the voltage at the bus terminal will increase. The bus voltage required for the 100kWh battery pack to achieve 4C fast charging is about 800V. In order to be compatible with the fast charging function of all models, the 800V electrical architecture has become the mainstream choice for fast charging.
Vehicle: High-end battle, 800V pile at the same time. In 2019, the luxury car brand Porsche launched the world's first 800V model, the Taycan. In 2020, BYD Han adopted an 800V architecture, and the e-platform 3.0 released at the 2021 Shanghai Auto Show is also equipped with an 800V architecture. Subsequently, Huawei, Geely, GAC, Xiaopeng, Lantu and other Tier1 and automakers/brands launched solutions at both ends of the pile to ensure the use of fast charging experience.
We believe that the next two years of high-end is the main battlefield of automakers, and the arms race has begun. Time is one of the core shortcomings faced by electric vehicles, and upgrading the 800V structure is conducive to achieving fast charging and forming a differentiated competitiveness for low-end models in the short term. Long-term fast charging is also just needed for low-end models, and the 800V architecture upgrade has a long-term trend.
Components and components: SiC and negative electrode benefit the most, and other components are smoothly upgraded. Upgraded from the current 400V to 800V, the components and components that have changed the most are mainly power semiconductors and battery anodes. Among them, SiC-based power semiconductors are expected to completely replace Si-based power semiconductors due to their excellent performance of high withstand voltage, low loss and high switching frequency.
Since the bottleneck of fast charging lies in the negative electrode, if the current 1C charge rate is increased to 2C, and then increased to 4C, the mainstream technology includes graphite-coated/doped hard carbon and silicon carbon anode. The rest of the components need to be re-selected to improve the pressure resistance level, but the overall cost change is smooth. In the short term, the high-pressure solution is about 2% higher than the current vehicle cost, and in the long run, it is expected to be lower than the current cost, which has established a good foundation for the promotion of the automaker.
Risk factors: sales of new energy vehicles are less than expected, the development of fast-charging battery technology is less than expected, the laying of fast-charging charging piles is not as expected, the expansion of the power grid is not as expected, and fast charging leads to battery safety problems.
Investment proposal: The next two years is the best time window for OEMs to move up, high-end models are expected to be launched intensively, and the arms race will begin. Shortening the energy replenishment time is one of the core demands of the current electric vehicle upgrade, and domestic and foreign automakers are competing to lay out 800V fast charging, taking the lead in configuring high-end vehicles, and forming a differentiated competitiveness for low-end models in the short term. In the long run, low-end models also have fast charging needs, and 800V electrical architecture upgrades have a long-term trend.
01
Motivation: Why 800V
Automotive voltage platform evolution
Fuel Vehicle Era, 6V-12V-48V:
In 1912, cars began to install batteries with a voltage of 6V. With the increase in electrical devices such as automotive appliances such as lights, lighting, ANDGs, the demand for electrical power increased, which was upgraded to 12V in 1950 and continues to this day.
During this period, there were also 42V, mainly initiated by the United States, but could not be realized due to the high cost of upgrading the voltage specification of the parts. In 2010, the demand for infotainment and hybridization appeared, and the 48V upgrade was initiated by Europe, coexisting with 12V.
In the era of electric vehicles, there is > 400V high voltage:
In pure electric vehicles, due to hundreds of battery strings in parallel, the entire battery pack voltage exceeds 100 volts, forming a high and low voltage two sets of electrical systems with the 12/48V appliances commonly used in fuel vehicles.
The high-voltage system of pure electric vehicles is mainly composed of power battery, distribution box, OBC, DCDC, electric drive, PTC, air conditioning, charging port, etc.
At present, pure electric passenger cars have different battery levels in the range of 250-450V, and buses/logistics vehicles have a battery pack voltage range of 450-700V after the battery pack is connected in series due to the high load capacity.
In the future, passenger cars are expected to be upgraded to 800V.
Pain points: energy replenishment speed, two schemes - power exchange and fast charging.
Electric vehicles surpass fuel vehicles in terms of power performance and intelligence, and the mileage is also increased to more than 400km with the increase of battery energy density and the reduction of power consumption. But the whole is still facing the problem of replenishment anxiety, the fuel car refueling time is 5 minutes, and the current fast charge is at least 60 minutes. The waiting time in line during peak charging periods is further lengthened.
The two routes to solve the speed of energy replenishment include power exchange and fast charging, and power exchange is still facing challenges such as profit model and unified standards.
At present, car companies choose more fast charging routes, on the one hand, fast charging is consistent with the CTC trend, on the other hand, the technology upgrade path is clear.
Fast charging: two technical directions: According to P = UI, there are 2 schemes to increase the power of fast charging.
Boost U, which stands for Porsche's 800V solution, 350A current, achieves 300kW charging power.
Boost I, Tesla super fast charging solution, has a huge challenge to thermal management, 600A current, to achieve 250kW charging power.
Fast charge: Why at least 800V?
In order to upwardly compatible high-end cars with large battery capacity. Battery charging speed is measured in current multiplier (C). In practice, the limitations are:
The charging gun has a maximum charging current limit;
Different EVs have different battery capacities, and they all have to achieve a considerable fast charging time.
Do a simple arithmetic: suppose you ignore the battery pack internal battery connection method, the capacity of 75/100kWh battery pack, the requirements also to achieve 7.5 minutes full (
Therefore, in order to be upwardly compatible with the fast charging performance of large high-end vehicles with battery capacity, the vehicle voltage level was set at 800V at the beginning of the design, and the internal battery cells of the battery pack were also designed with 800V as the standard string parallel topology, and finally the battery cell capacity was determined.
For example, in a 400V system, if it is a ternary cell, it needs 400/3.6=112 series nodes; if the 4 cells are connected in parallel, a total of 448 cells are required. If the battery pack capacity is 100kWh, the capacity of a single NCM cell is 62Ah, and the corresponding cell connection method is 4 and 112 strings. Under the 800V system, if the cell specifications remain unchanged, the cell connection method becomes 2 and 224 strings.
What are the benefits of upgrading 400V to 800V?
The specification of the high-voltage wiring harness decreases, the dosage decreases, the cost is reduced and the weight is reduced, and the series increases and the high-voltage wiring harness current becomes smaller in the case of doubling the voltage and the charging power increase is not doubled.
SiC inverter makes the power supply frequency increase, the motor speed increase, the torque decreases at the same power, and the volume decreases. The motor voltage doubles, the current is halved at the same power, so the copper wire is thin (but the number of turns increases, so the amount of copper used is not reduced), the current density is small, and the torque becomes smaller. If the power needs to be increased, the rated current only needs to increase from half of the rated current of the 400V motor.
02
Vehicle: High-end battle,
800V pile lifting
Phase 1: 800V system on the vehicle end
Start the app
Porsche Taycan's TurboS led the 800V wave, and independent brands, overseas joint ventures and new car-making forces have followed up on the layout of 800V.
The second stage: 800V car piles are lifted at the same time, becoming
Brand upgrades come standard
Guangzhou Auto Show car companies will fight high-end, consumer acceptance of trams ushered in a clear inflection point, the next two years are expected to be the best stage for brand upwards.
High-end cars are shorter than weaknesses, and low-end cars are better than strengths. In the process of high-end upgrading, the configuration of stacks and refueling is a common pain point faced by various car companies, and long-term fast charging will become the standard. In addition, rapid replenishment is also just needed for low-end cars, and under the premise that the development speed of the power exchange route is relatively slow, fast charging has the potential to sink.
The complete experience of fast charging requires the simultaneous cooperation of both ends of the pile. In the short term, the popularity of 800V fast charging piles is limited, so car companies choose to promote 800V (Xiaopeng, Lantu, etc.) at both ends of the pile, and there are also parts suppliers such as Huawei to provide complete fast charging solutions.
What is the difficulty of 800V high voltage platform? —
- Technology + infrastructure are jointly promoted
The 800V high-voltage platform faces multiple difficulties, including the redevelopment of related components, the improvement of battery module safety, and the change of semiconductor device route.
Most of the original components had to be redeveloped and redesigned to match the high-voltage platform. This puts forward new requirements for car companies and suppliers.
800V fast charging poses a challenge to existing batteries, and the charging rate of more than 4C and the increase in voltage and current greatly affect the stability of the battery. Further improvements in the conductivity of BMS and battery materials are still needed.
In terms of semiconductor devices, IGBTs are commonly used on 500V voltage platforms, and SiC is better than IGBTs on 800V voltage platforms.
The realization of 800V fast charging performance requires 800V capacity at both ends of the pile, and at the same time, the power grid is also required to increase capacity.
03
Components and components: SiC and negative electrode benefit the most,
Smooth upgrade of other parts
400V->800V Which parts and components need to be upgraded?
Electronically controlled
SiC performance at 800V is excellent, and the trend of replacing Si-based power semiconductors is clear:
SiC base power semiconductor compared to Si base has a higher withstand voltage level and switching loss, to Si-IGBT as an example, 450V under its withstand voltage of 650V, if the automotive electrical architecture is upgraded to 800V, considering the switching voltage switch overload and other factors, the corresponding power semiconductor withstand voltage level needs to reach 1200V, and si-IGBT under high voltage Switching / Conduction loss increase sharply, facing the problem of rising cost and energy efficiency reduction.
SiC has excellent voltage resistance, switching frequency and loss performance at 800V, and is the biggest beneficiary component under the 800V trend.
Film capacitors increase the withstand voltage level, and the value of bicycles increases in the short term:
The role of the film capacitor is to act as a DC support capacitor, absorbing high pulse current from the DC-link end and protecting the power semiconductor. Generally a power semiconductor with a film capacitor, new energy vehicles are mainly used for motor controllers, OBC, if there are multiple motor models, the amount of film capacitors will also increase. In addition, a film capacitor is also required on the DC fast charging pile.
At present, the ASP of film capacitor is 200 yuan, and under the trend of 800V, the ASP of film capacitor needs to be increased by about 20%. In addition, in the short term, 800V will be the first application in high-end cars, and high-end cars generally use multi-electric drive configurations to increase the amount of film capacitors.
battery
Negative extreme fast charging performance requirements are improved. The constraint of the fast charging performance of the power battery lies in the negative electrode:
On the one hand, the layered structure of graphite materials causes lithium ions to enter only from the end face, resulting in a long ion transport path;
On the other hand, the graphite electrode potential is low, and the polarization of the graphite electrode under high magnification and fast charging is large, and the potential is easy to drop below 0V and the lithium is analyzed.
There are two main types of workarounds:
Graphite modification: the surface is coated and mixed with amorphous carbon, and the amorphous carbon is a highly disordered carbon layer structure inside, which can realize the rapid embedding of Li+.
Silicon anode: the theoretical capacity is high (4200mAh/g, much larger than the carbon material 372mAh/g), and the intrinsic reason for fast charging is that the embedded lithium potential is high - the risk of lithium evolution is small - and can tolerate a larger charging current.
Motor
Bearing corrosion protection and insulation requirements have increased. Generation of shaft voltage:
The motor controller is powered by a frequency conversion power supply, containing a high-order harmonic component, and the inverter, stator winding, and chassis form a loop to generate an induced voltage, called a common-mode voltage, which generates a high-frequency current on this loop. Due to the principle of electromagnetic induction, the induction voltage is formed at both ends of the motor shaft, which becomes the shaft voltage, which is generally unavoidable.
Rotor, motor shaft, bearing to form a closed loop, bearing balls and the inner surface of the raceway for point contact, if the shaft voltage is too high, easy to break through the oil film after the formation of a circuit, shaft current occurs leading to bearing corrosion;
The application of SiC in the 800V inverter leads to a high frequency of voltage change, an increase in shaft current, and an increase in bearing corrosion protection requirements;
At the same time, due to the increase in voltage/switching frequency, the insulation/EMC protection level requirements inside the 800V motor are increased.
HVDC relays: high performance requires drive added value,
The value of bicycles has increased
The demand has high certainty, the product performance requirements under 800V are improved, and the added value is improved:
As an automatic control switch element, the HVDC relay plays a role in high voltage circuit control and safety protection, and the new energy vehicle has a rigid demand for HVDC relay;
800V platform voltage current is higher, the arc is more serious, the high voltage DC relay withstand voltage grade, current carrying capacity, arc extinguishing, service life and other performance requirements are improved, the product needs to be improved in contact materials, arc extinguishing technology and other aspects, added value is improved.
It is expected that the value of bicycles will increase by 40%, and the number of passenger car configurations will be mainly 4-5, and the charging pile will be more than 2:
At present, the value of A-class vehicle high-voltage relay bicycles is about 800 yuan, and it is expected that the value of bicycles on 800V voltage platforms will increase by 40%. The number of configurations depends on the model type and circuit design, and the passenger car mostly adopts 2 main circuits, 1-2 fast charging circuits, and 1 pre-charging circuit;
Commercial vehicles have higher power, equipped with about 4-8, and DC charging piles are conventionally equipped with 2.
Fuse: the permeability of the excitation fuse is improved,
With the rigidity of demand, circuit protection requires product innovation such as drive excitation fuses and intelligent fuses, and the value is enhanced:
The fuse is a circuit overcurrent protection device, 800V requires the fuse to be improved and adjusted in terms of insulation and withstand voltage grade;
The new excitation fuse stimulates the protection action by receiving the control signal, and has been gradually applied to new energy vehicles, and the average selling price is 3.6x of the traditional power fuse;
The intelligent fuse automatically detects the circuit signal to trigger the protection action, which is still in the early stage of development and application.
It is expected that the value of the bicycle will increase by about 20%, and the penetration rate of the excitation fuse will increase: the current fuse pen value is about 200-250 yuan, the conservative scheme under the 800V platform adopts the thermal fuse and the excitation fuse, the radical scheme only uses the excitation fuse, with the continuous improvement of the market penetration rate of the incentive fuse, the value of the bicycle is expected to reach 250-300 yuan.
High voltage connector: current reduction and drop specification,
Welcome domestic substitution opportunities
Performance upgrade, advantages of manufacturers have obvious advantages: as a bridge for the high-voltage current loop of new energy vehicles, the requirements for the reliability, volume and electrical performance of the connector will increase, and its mechanical properties, electrical properties and environmental performance will continue to improve.
As a high-end product, the high-voltage connector of electric vehicles has high technical and process barriers. The low-voltage connectors of traditional fuel vehicles are monopolized by overseas suppliers. The rapid growth of electric vehicles opens up the new increase in high-voltage connectors, technical changes require rapid response, and the high-voltage vehicle platform will further improve industry barriers, and domestic suppliers will usher in domestic replacement opportunities.
The number of increased, the value of bicycles is expected to increase: at present, a single electric vehicle is equipped with 15-20 high-voltage connectors, and the unit price is between 100-250 yuan, and the demand for dual motor or high-power drive motor models is more. After increasing from 400V to 800V, the high-voltage connector will be re-selected, and the high-power fast-charging interface and the conversion interface from 400V to 800V will be added, driving the value of high-voltage connector bicycles to rise.
OBC/DCDC: Active Component Upgrade,
Benefit boost increments in the short term
High voltages place higher demands on power devices and will drive OBC/DCDC costs to climb in the short term:
In order to meet the more stringent requirements brought by the 800v high-voltage platform in terms of volume, light weight, withstand voltage, high temperature resistance, etc., the integration trend of power devices such as OBC/DCDC is obvious;
At the same time, it is expected that SiC silicon carbide will be widely used in the field of power devices with the advantages of high voltage resistance, high temperature resistance and low switching loss, and the value of driving bicycle OPC/DCDC will increase by about 10%-20%.
The 800v high-voltage platform is expected to bring new additions to OBC/DCDC:
The high-voltage platform increases the demand for on-board charger upgrades, providing incremental increments for high-voltage OBC;
At the same time, in order to be able to adapt to the use of the original 400v DC fast charging pile, the new car equipped with the 800v voltage platform must be equipped with an additional DCDC converter to boost the voltage, further increasing the demand for DCDC.
Soft magnetic alloy powder core: boost module
Increase usage requirements
The main material of the inductive element is made of metal magnetic core:
800V system upgrade, in the short and medium term in order to adapt to the existing 400V charging pile, it is necessary to install a DCDC boost module, and the independent boost module needs additional inductance. The amount of bicycle consumption has been increased from 0.5kg to about 2.7kg;
Due to the small battery capacity, the voltage cannot be achieved by series 400V, and the demand for boost DCDC is greater. In general, the amount of pure electric/plug-in hybrid bicycles is 0.5/4kg.
Charging pile: high voltage fast charge is faster than low voltage high current charge
Save about 5% of the cost
At the same power, due to the reduction of the current, the voltage from 400v to 800v still does not require liquid cooling, and the future 500A will require the addition of a liquid cooling system.
400V-800V vehicle cost change smooth,
Good for the promotion of automakers
In terms of vehicle cost, the cost of high-voltage architecture is +2% higher than that of low-voltage architecture.
The battery side has a cost of +5% due to the improvement of negative extreme fast charging performance and the increase in BMS complexity;
From the perspective of vehicle components, the high-voltage architecture has little cost change in thermal management, cable accessories and other components, which is better than the low-voltage and high-current architecture.
800V beneficiary plate bicycle value and industrial chain target:
Remarks: The article is reproduced from Tamshi Capital