Automotive 800V overcharging technology (2) - 800V overcharging architecture-EEWORLD

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Last time we mentioned the market and car factory layout of 800V overcharging. This content focuses on explaining the structure of 800V overcharging.

Automotive 800V Supercharging Technology (1)—Market & Car Factory Layout

1. High-power charging can be achieved through high voltage or high current, and fast charging through high voltage is more mainstream.

As mentioned in the first article above, charging and battery life are the core pain points; charging time = battery capacity /charging power. The charging time of an electric vehicle mainly depends on the battery capacity of the vehicle and the charging power of the charging pile . The larger the battery capacity, the stronger the endurance. Improving the battery capacity of electric vehicles is one of the trends. Under the same charging power, the longer charging time is required. The greater the charging power, the faster the charging speed, and the shorter the charging time required. Therefore, high-power fast charging is one of the most important ways to solve energy replenishment anxiety.

Charging power = system voltage × charging current . Charging power is determined by system voltage and charging current. Therefore, there are two technical routes to achieve high-power fast charging: one is high-current fast charging technology, and the other is high-voltage fast charging technology. However, the disadvantages of high-current fast charging are obvious. Currently, high voltage has become the main trend of fast charging.

High current fast charging technology

The current level of promotion is low. The material system and structure of the battery cell need to be upgraded to increase the maximum charging current of the single battery cell, and a thicker wire harness needs to be used, which will increase the volume and weight of the charging components and affect the convenience of user operation. At the same time, the heat generated during high-current charging increases significantly, causing greater heat dissipation problems, easily causing safety hazards, higher thermal management requirements, and greater technical difficulty. Moreover, the energy loss is serious and the conversion efficiency is low. In addition, the high current mode only performs maximum power charging at 10%-30% SOC, and the charging power in other ranges is significantly reduced. The application of this path is represented by Tesla Model 3.

High voltage fast charging technology

It is currently the mainstream choice for car companies to achieve fast charging. Under a high-voltage system, the efficiency of the electric drive system of electric vehicles will increase, thereby increasing the cruising range. Compared with the high current mode, the high voltage mode has the advantages of larger efficient charging SOC range, higher charging power peak, relatively less technical difficulty, and relatively controllable costs. The application of this path is represented by German car companies and domestic independent brands, and the voltage platform has been increased from 400V to 800V.

2. Charging power ≥300kW can be called super fast charging, and high voltage is the high-limit technology path for the future.

According to the characteristics of the current market technology level, the maximum charging power of super fast charging needs to be greater than or equal to 300kW, that is, the maximum power of the charging pile and the peak charging power of smart electric vehicles must reach the level of 300kW+.

Under the standard of super fast charging, the high-voltage technology path is realized through the upgrade of the 800V architecture of the entire vehicle. The charging voltage is not less than 750V and the current is not less than 400A. This technology path is future-oriented and subversive, and its advantage is development The upper limit is high, charging and power consumption are low, and it is light weight and small in size, with many potential players; the disadvantage is that the hardware cost is high and the industry is not yet mature.

The high-current technology path achieves super-fast charging through the upgrade of thermal management and battery management systems . The charging voltage is not less than 375V and the current is not less than 800A. This technology path is current-oriented and progressive. The advantage is that the technology is mature and does not require The car-side hardware is modified and applicable to already sold products; the disadvantages are high charging loss, limited technological development limit, and fewer players.

3. 800V mainstream architecture solution

Solutions for realizing high-voltage fast charging in automobiles can be simply divided into three categories according to the battery and voltage system, namely 800V power battery and 800V high-voltage system, 800V power battery and 400V high-voltage system, and 400V power battery and 400V high-voltage system. Considering factors such as the voltage boosting method, it can be subdivided into five solutions. From the current comprehensive solution promotion difficulty and transformation cost, solution one (all 800V charging systems are compatible with 400V fast charging) is better and is expected to become the mainstream solution.

Option 1: All vehicle components are 800V, and the electric drive boost is compatible with the 400V DC pile solution. Its 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, it is compatible with 400V DC charging piles.

Option 2: All vehicle components are 800V, and a new DCDC compatible 400V DC pile solution is added. Its 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.

Option 3: All vehicle components are 800V, the power battery can flexibly output 400V and 800V, and is compatible with the 400V DC pile solution. Its 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, and are compatible with 400V DC charging piles.

Option 4: Only the DC fast charging related components are 800V, the rest of the components are maintained at 400V, and DCDC components are added for the voltage converter solution. Its typical features are: only DC fast charging and power batteries are 800V; AC slow charging, electric drive, and high-voltage components are all 400V; a new 400V-800V DCDC is added to realize voltage conversion between 400V components and 800V power batteries, and is compatible with 400V DC charging pile.

Option 5: Only DC fast charging related components are 800V, the rest of the components are maintained at 400V, and the power battery can flexibly output 400V and 800V solutions. Its 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, and are compatible with 400V and 800V DC charging piles.