1. High-power flexible battery stacks may become the mainstream fast charging solution
The traditional integrated charging piles have a fixed power that cannot match the higher-voltage charging requirements, and there is a problem of not being "upward compatible". In the process of "downward compatibility", the construction of integrated 800V charging piles has the dilemma of wasting performance and high unit investment costs. The flexible battery stack brings together all the charging modules of the electric vehicle charging station, and dynamically allocates the charging modules according to the actual charging power required by the electric vehicle through the power switching unit. It can replenish energy for multiple electric vehicles at the same time, and is expected to become a mainstream high-voltage fast charging solution.
2. Liquid cooling technology is expected to be popularized to cope with the problem of heat generation in high-power fast charging
The high-power charging brought by 800V will cause high heat generation power and overheating problems in the charging system, which is an important challenge facing the current fast charging of electric vehicles. Traditional air cooling technology can hardly meet the heat dissipation requirements of charging piles with power of hundreds of kilowatts, while liquid cooling is more suitable for high-rate charging and discharging scenarios. Liquid cooling technology sets a special liquid coolant between the cable and the charging gun, which is driven by a pump to circulate in the cable and the charging gun, taking away the heat during the charging process and returning to the liquid cooling source radiator, thereby increasing the cable transmission power and achieving high-power charging. Compared with the traditional air cooling mode, the liquid cooling mode has the characteristics of high safety, fast charging, long life, and low operation and maintenance costs. Taking Huawei's 600KW full liquid cooling solution as an example, although the initial investment cost is relatively high, it can reduce secondary investment, and the life cycle cost TCO is reduced by about 40%.
3. The concentration of high-voltage fast charging will bring pressure to the power grid. Energy storage system configuration may be a solution
The concentrated use of high-power charging piles will put pressure on the distribution network. The network loss rate is an important indicator for evaluating the economic efficiency of the power grid. According to the formula network loss rate = (network loss power/power supply) * 100%, in the case of disorderly charging of electric vehicles, the average network loss rate of the distribution network rises from 7.85% to 10.14%, which shows that disorderly charging of electric vehicles often coincides with the peak hours of daily electricity consumption of residents. In the case of 800V supercharging, concentrated charging at peak times puts higher requirements on the load capacity of the distribution network. The energy storage system refers to a system that converts energy into other forms of storage so that it can be converted into usable energy when needed. The energy storage system configured at the charging station can store electricity during low electricity consumption and charge during peak electricity consumption, smoothing the high-voltage curve of the charging station and reducing the loss of the distribution network.
4. The power device in the charging module is upgraded from SiIGBT to the third-generation semiconductor SiC MOSFET
As the core component of the DC charging pile, the charging module accounts for about 50% of the overall cost of the charging pile, and the power device is an important component of the charging module. At present, one of the technical challenges faced by 800V DC charging piles is that as the voltage and charging level increase, the charging module needs to have higher high voltage resistance and power density. 800V high-voltage charging increases the constant power range of the charging module from 400V-750V to 800V-1000V, while the commonly used SiIGBT power device has a withstand voltage upper limit of 750V, which needs to be upgraded to a SiCMOSFET chip with a withstand voltage upper limit of more than 1200V. In addition to its outstanding high-voltage resistance performance, compared with traditional silicon-based devices, SiC modules can increase the output power of the charging pile by nearly 30% and reduce losses by about 50%.
5. Liquid cooling modules have significant advantages, but the current cost is high and in the introduction stage
With the increase in the power of charging piles, charging modules need to withstand greater power density. The power of a single module is mainly 30-40KW, which reflects the need for stronger heat dissipation. Compared with the current air-cooled modules, the advantages of liquid cooling modules include long life, high efficiency, and strong heat dissipation. However, due to the high cost of liquid-cooled charging module equipment, the selling price is more than twice that of air-cooled modules. Liquid cooling modules are in the initial stage, and many companies are actively deploying liquid cooling modules. It is expected that as the cost decreases, the penetration rate will gradually increase.
6. Liquid-cooled super charging guns have become the future technology route with their advantages of high current, light weight, and plug-and-play charging
The high-power working environment also puts higher requirements on charging guns. The maximum current of conventional natural cooling charging guns is 250A, while liquid-cooled charging guns use oil cooling/water cooling to dissipate heat, and the maximum charging current can reach more than 500A. At the same time, compared with conventional charging guns, they can reduce weight by nearly 50%. But similarly, the price of liquid-cooled charging guns is still at a relatively high level. According to the new product briefing of Rifeng Co., Ltd. in 2022, domestic liquid-cooled charging guns are still in the initial stage, and the market unit price exceeds 20,000 yuan, while the price of conventional DC charging guns is 1,000-2,000 yuan. With the demand for liquid-cooled charging guns brought about by the promotion of 800V fast charging, it is expected that the penetration rate of liquid-cooled guns will break through.
7. Liquid-cooled supercharging cables have the advantages of large current, light weight, thin wire diameter, and fast heat dissipation
The cables connected to the domestic standard DC charging guns are mainly 35mm2, which can carry 125A current. Taking the charging power of 400KW as an example, at a voltage of 800V, the current to be carried is 500A, and the cross-sectional area needs to be increased to reduce the heat caused by the increase in current. There are liquid cooling pipes in the liquid-cooled cable, and the coolant can take away the heat generated by the cable. The cable diameter of a 500A liquid-cooled charging gun is usually only 35mm, and its weight is about half of that of a traditional cable. At the same time, it can reduce the heat damage caused by high-power charging.
