Electric vehicles are receiving increasing attention as an important mode of transportation in the future. The industry has been focusing on the “slow charging and difficult charging” issue of new energy vehicles, especially with the growing application of pure electric vehicles. To address this issue, liquid-cooled supercharging technology has emerged as a new solution and has become a key area of competition in the industry.
1. Liquid-cooled System introduction
It is widely acknowledged that many manufacturers are investing in supercharging technology. Porsche, Tesla, Xiaopeng, Ideal, EAN, Kryptonite, Huawei, and numerous other manufacturers have released supercharging solutions, and car companies are striving to dominate the high-power fast-charging market. Although there are vehicles capable of super-fast charging, they still require super-fast charging stations. The upstream and downstream enterprise layout is expected to accelerate the development of supercharging technology.
In October 2023, Huawei Digital Energy released a fully liquid-cooled supercharging station on the Sichuan-Tibet line. The station has a maximum output power of 600kW and a maximum current of 600A, and is capable of charging “one kilometer in just one second”. The full liquid-cooled EV supercharging station provides a fast and convenient charging experience, alleviating the charging anxiety of electric car owners. Its landing will accelerate the popularization of high-power fast charging.
What is liquid-cooled supercharging?
Liquid-cooled supercharging is a high-efficiency charging technology achieved through liquid cooling. Heat generated during charging is taken away through liquid circulation to achieve fast and stable charging. Currently, high-power fast charging mainly focuses on two aspects: increasing the vehicle battery voltage and enhancing the charging current. The voltage of pure electric new energy vehicles has increased from the original 400V to 800V or even 1000V. Similarly, the charging current has been enhanced from the original 160A to 250A, and even up to 600A for supercharging. The charging speed is mainly improved under the condition of the vehicle battery voltage. Improve the charging current. However, increasing the charging current will also increase the heat generation of the terminals and cables, leading to a rapid rise in temperature. This sustained high temperature can cause damage and, in serious cases, lead to safety accidents such as burnouts.
Joule’s law states that the heat generated by the current through a conductor is proportional to the square of the current, the resistance, and the energization time. Therefore, if the resistance and energization time remain constant, the heat generated by the EV charging station increases with the current. When charging with a 250A charging current, 62,500 joules of heat are generated using one charging gun or two charging guns under the same resistance and time. However, when charging with a 600A charging current, 360,000 joules of heat are generated. Therefore, the heat dissipation capacity of the charging gun needs to be greatly improved. Similarly, the heat capacity of the fan in the charging station also needs improvement.
The vehicle battery system can use liquid cooling to dissipate heat and prevent safety accidents. To achieve this, we must reduce the heat and temperature rise of the charging gun terminals and cables. Increasing the cross-sectional area of the conductor is a possible solution. However, increasing the cross-sectional area of the conductor after the cable weight has increased and during cable usage can make it difficult to bend, resulting in abnormal use by the user. To address this issue, liquid-cooled high-power charging technology can significantly reduce the cross-sectional area of the cable and make the charging gun cable lighter, improving the user’s operating experience.
The liquid-cooled charging gun is not only faster but also 30% to 40% lighter than conventional charging guns. Compared to the traditional super-charging cable, it can be easily used by anyone, even those girls who are more delicate. The principle of full liquid-cooled supercharging involves creating a liquid circulation channel between the cable and the charging gun. This channel is used to dissipate heat and is joined by the liquid coolant. The power pump promotes the circulation of coolant to remove the heat generated during the charging process. The charging host’s power component uses liquid cooling to dissipate heat. This design allows for an IP65 rating. The system also has a large, low-noise fan for heat dissipation that is environmentally friendly.
The liquid cooling circulation system drives the circulation of liquid to cool the charging station, charging gun, and other electrical equipment. This ensures equipment stability and prolongs its lifespan. The system extends from the charging station to the charging cable and connector, enabling low-temperature operation of the entire charging system. This improves cooling performance, increases power density and output of the equipment, and is a significant improvement over traditional air-cooled technology.
2. Advantages of fully liquid-cooled supercharging
What are the advantages of fully liquid-cooled supercharging? Is it just faster charging? Liquid-cooled cooling technology “one kilometer per second”, “highly reliable equipment”, “matching all car models”, charging to ensure a 10-year service life of the equipment, power sharing to increase the utilization of utility power by 30%, etc. realize the whole life cycle TCO decrease by 40% and so on.
Some of the advantages of this technology are described below.
(1) Faster charging is the primary advantage of liquid-cooled EV charging station. This technology adopts liquid cooling technology to improve heat dissipation efficiency during the charging process, resulting in increased charging current and faster charging times. The goal is to achieve a charging speed of “one second, one kilometer”, which may eventually be comparable to refueling speeds. The charging station has high efficiency and can meet the needs of many vehicles. Vehicle owners can charge at any time for convenience.
(2) Using a lighter cable can provide a better experience. Thickening the cable to reduce heat is unnecessary due to its strong heat dissipation ability. The 250A GB/T national standard charging gun typically uses an 80mm2 cable, which makes the overall weight of the charging gun very heavy and difficult to bend. Liquid-cooled charging guns have cables and water pipes inside, and the cables of 500A liquid-cooled charging guns are usually only 35mm2. The flow of coolant inside the water pipes takes away the heat. The liquid-cooled charging gun is 30% to 40% lighter than conventional charging guns due to its thin cable, making it easy to use even for those with less strength.
(3) High reliability and long service life: Liquid-cooled charging station has high reliability and service life. Conventional charging station and semi-liquid-cooled charging station are air-cooled, with the air entering the charger from one side, blowing away the heat of the electrical components and rectifier module, and dispersing from the other side of the charger. The air will be mixed with dust, salt spray and water and adsorbed on the surface of internal devices, resulting in poor system insulation, poor heat dissipation, low charging efficiency and reduced equipment life. Liquid cooling technology, liquid heat exchange is in a closed environment, the charging module has no direct contact with the outside world, the protection level can be IP65, reducing dust and other contact with electronic devices, higher reliability. And it is liquid cooling, cooling more evenly and effectively, can effectively reduce the temperature inside the EV charger during the charging process, reduce the failure rate of the charger, improve the service life of the equipment.
(4) Match all models: Liquid-cooled charging station can match all models, and generally liquid-cooled supercharging technology adopts a common charging connector standard. Whether it is electric vehicle, hybrid vehicle or fuel cell vehicle, all can use liquid-cooled charging station. It can recognize the vehicle model, and when the vehicle cannot accept supercharging, it can charge at the maximum current that the vehicle can accept. This makes the liquid-cooled charging station have a wider application range and higher utilization rate.
(5) Low charging noise. The charging station is liquid-cooled and uses a dual-circulation cooling structure. The internal module is cooled by liquid, which is circulated by a water pump to transfer heat to the finned radiator. The external charging station is also liquid-cooled and uses a low-speed, high-volume fan or air conditioner to dissipate heat from the radiator. This fan produces much less noise than a high-speed, small fan. The super charging station can be fully liquid-cooled and adopt a split cooling design, similar to split air conditioning. This design places the noisy cooling unit far away from the crowd or even uses heat exchange with pools and fountains to achieve better cooling and lower noise.
(6) Low TCO: When considering the total life cycle cost (TCO) of charging station, it is important to factor in the cost of charging equipment at charging stations. Traditional charging station with air-cooled charging modules typically have a lifespan of less than 5 years. However, the lease period of charging stations is usually 8-10 years, which means that EV charger will need to be replaced at least once during the operating cycle of a charging station. In contrast, a fully liquid-cooled charging station has a service life of at least 10 years, which can cover the entire life cycle of the station. Additionally, unlike air-cooled charging station that require frequent cabinet openings for dust removal and maintenance, full liquid-cooled charging station only need to have their external radiator flushed after accumulating dust, making maintenance simple. The total cost of ownership for the full liquid-cooled charging system is lower than that of the traditional air-cooled charging module system. The full liquid-cooled system is widely used in large quantities, making its cost-effective advantage more apparent.
(7) Promote the popularization of electric vehicle market. Once the charging issue of new energy vehicles is resolved, the user experience will significantly improve. This will alleviate any doubts users may have about long charging times, accelerate the construction of charging facilities, expand coverage, and encourage more people to choose electric vehicles.
3. Disadvantages of full liquid-cooled EV supercharging
The full-liquid-cooled supercharging station can be said to be in its infancy, and there are many problems that need to be solved, and perhaps some of them need to be discovered and perfected in the application.
(1) At present, the cost of full liquid-cooled supercharging station is higher compared with traditional air-cooled charging station. This may be able to reduce the cost by volume after full popularization.
(2) At present, in a high temperature environment, the heat dissipation performance of the liquid will have a certain impact, which in turn reduces the charging efficiency.
(3) Maintenance may be more complicated. Liquid-cooled supercharging systems require regular inspection, cleaning and replacement of the liquid, making maintenance more difficult.
(4) Technological development in terms of battery life and quality. Supercharging is not only about the output of the charging station, but also about the battery’s ability to withstand it. Experience shows that fast charging and discharging can have a negative impact on battery life. Although some companies currently offer 3C, 4C, and other ultra-fast charging power batteries, the technology’s maturity needs further testing. Additionally, there have been incidents of vehicle charging fires even with slow charging. hope that the charging speed and battery safety are comprehensively improved, while also guaranteeing battery life.
(5) A high-power charging station usually requires multiple EV chargers. Therefore, when designing a supercharging station, the impact on the distribution network’s power supply and even the power grid should be taken into consideration. However, an PV storage and charging station that uses photovoltaic power generation and energy storage as a supplement is also a feasible solution. It can reserve power when electricity is cheap and the power supply is sufficient, and use stored power when electricity is expensive and demand for power is high. This approach can reduce the direct impact of super-fast charging on the grid, alleviate electricity pressure, and reduce power consumption costs.
Liquid-cooled supercharging is a technical trend that improves charging efficiency and safety while adapting to various models and environments. It provides fast, stable, and safe charging services for new energy vehicles. It is significant in solving the long-distance running range problem of electric vehicles and provides new opportunities for the development and popularization of new energy vehicles. This technology has broad market prospects and development space. It can promote orderly charging and V2G, help with energy conservation and emission reduction, low-carbon green development.
