The core of fast charging is to increase the charging power of the vehicle. There are two main ways to increase the charging power, increasing the charging current or increasing the charging voltage. At present, most traction inverters of pure electric vehicles use 600V IGBT modules, so the battery pack voltage is limited to a peak value of around 400V. If the charging voltage is kept at 400 V, increasing the current will cause the charging cable to be bulky and conduction heat loss square As the level increases, the resistance of connectors, cables, electrical connections to batteries, busbars, etc. will heat up. Increasing the bus voltage to 800 V can double the charging power of the same cable, and to achieve ultra-high charging power of 350 or 400kW, the 800V high-voltage platform came into being.
Compare a Tesla Model 3 with a 400V bus to a Porsche Taycan designed with an 800V bus. It takes 26 minutes and 22.5 minutes for Model3 and Taycan to charge SOC from 5%-80%, respectively. The Model 3 has a lower bus voltage and achieves a maximum charging power of 250kw by using a very high maximum charging current of over 600A. The Porsche Taycan uses an 800V battery pack that provides a maximum charging current of 340A and a peak charging power of 270kW through conventional DC fast chargers and plugs. The Taycan gets slightly more charging power than the Model 3, reaching 400 kW at 800 V bus and 500 A charging current. The 800V high-voltage architecture may become the mainstream platform for next-generation electric vehicles. The 800V high-voltage system usually refers to the system whose voltage range of the high-voltage electrical system of the whole vehicle reaches 550-930V, collectively referred to as the 800V system. The 800V high-voltage system has won the favor of many groups and brands with its low cost and high efficiency. Overseas Hyundai Kia, Volkswagen Group, Mercedes-Benz, BMW, etc., domestic BYD, Geely, Jihu, Hyundai, GAC, Xiaopeng, etc. all focus on 800V high-voltage platforms . The 800V high-voltage architecture is expected to become the mainstream vehicle voltage platform for next-generation electric vehicles.
According to United Electronics, there are currently five common 800V high-voltage system architectures:
Solution 1: All vehicle components are 800V, and the electric drive booster is compatible with the 400V DC pile solution. Typical features are: DC fast charging, AC slow charging, electric drive, power battery, and high-voltage components are all 800V; boosted by the electric drive system, compatible with 400V DC charging piles. This solution has low energy consumption for the whole vehicle and has no safety risk. All components requiring 800V are also products under research and development by the supplier, which is easy to promote.
Solution 2: All vehicle components are 800V, and a new DCDC compatible 400V DC pile solution is added. Typical features are: DC fast charging, AC slow charging, electric drive, power battery, and high-voltage components are all 800V; through the addition of 400V-800V DCDC boost, it is compatible with 400V DC charging piles. This solution has low energy consumption for the whole vehicle and no safety risk, but the cost of adding the system is relatively high, but it is still easier to promote because many manufacturers of 800V components are in research.
Solution 3: All vehicle components are 800V, and the power battery can flexibly output 400V and 800V, compatible with the 400V DC pile solution. Typical features are: DC fast charging, AC slow charging, electric drive, power battery, and high-voltage components are all 800V; two 400V power batteries are connected in series and parallel, and can flexibly output 400V and 800V through relay switching, compatible with 400V DC charging piles. This solution is difficult to promote because the power battery needs a special design to avoid potential problems of battery parallel circulation. Solution 4: All vehicle components are 800V, and the power battery can flexibly output 400V and 800V, compatible with the 400V DC pile solution. Typical features are: DC fast charging, AC slow charging, electric drive, power battery, and high-voltage components are all 800V; two 400V power batteries are connected in series and parallel, and can flexibly output 400V and 800V through relay switching, compatible with 400V DC charging piles. This solution has high energy consumption for the whole vehicle, and the advantage is that only one DCDC needs to be added, but this 400V/800V DCDC has high safety requirements and is not easy to promote.
Solution 5: Only the components related to DC fast charging are 800V, and the remaining components are maintained at 400V. The power battery can flexibly output 400V and 800V. Typical features are: only DC fast charging is 800V; AC slow charging, electric drive, and load are all 400V; two 400V power batteries are connected in series and parallel, and can flexibly output 400V and 800V through relay switching, compatible with 400V and 800V DC charging piles. Although the new cost of the system is low, and the difficulty of vehicle layout transformation is moderate, this solution is at a disadvantage in terms of energy consumption, special battery changes and design.
Considering performance, system cost, and the amount of vehicle transformation, Option 1, "All vehicle components are 800V, and the electric drive booster is compatible with 400V DC pile solution" is expected to be a solution that will be rapidly promoted in the short term.
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