Fast charging drives the development of liquid-cooled charging technology
1. Background
Driven by the trend of automobile electrification, the use of cyclically chargeable and dischargeable power batteries as the main energy source for automobiles has become the focus of the industry's development. However, in the market application of electric vehicles, due to the longer charging and recharging time than traditional fuel vehicles, and due to the energy density of power batteries and other reasons, the pure electric range of the vehicle is often not ideal, which gives rise to mileage anxiety and charging anxiety for users.
Based on the above background, car companies/related suppliers have launched implementation plans that meet the current stage of automobile development after multiple explorations. The summary can be divided into two stages. First, under the current technical background, by increasing the capacity of the power battery carried by the vehicle to solve the problem of insufficient range under pure electricity, this is also the shortest cycle and can be quickly applied to the market. Feasible solution. However, with the increase in the capacity of the power battery, the vehicle's range problem has been alleviated, but it has also further led to the extension of the charging time, which makes the charging anxiety problem more prominent. For new energy vehicles, the convenience of charging and the length of the recharging time are one of the important factors restricting its rapid development. Therefore, on the basis of Phase I, in order to solve the charging anxiety and promote the penetration of new energy vehicles, the industry currently adopts a basically consistent solution, that is, to replenish the whole vehicle through fast charging to shorten the charging time.
2. Liquid cooling charging technology
With the promotion of fast charging technology, high-power charging will become the mainstream. With the advent of the era of high-voltage and high-current charging, the heat generated by the charging pile will be much higher than the current charging state due to the presence of strong current during the charging process. Therefore, in order to meet the charging needs of the whole vehicle at higher power, the cables and connectors of the charging pile will become more cumbersome with the increase of charging current. And this more cumbersome charging gun and cable will be less friendly to users with poor physical fitness. At the same time, as the core unit of the charging pile, the charging module currently mainly uses forced air cooling for heat management. However, due to the increase in charging power, the air cooling method has problems such as uneven heat dissipation, poor heat dissipation effect, and high noise, which makes it not ideal in actual application, and there are also safety hazards caused by heat dissipation.
In order to adapt to the development of the industry and the market, charging piles as the infrastructure of new energy vehicles are also facing technological innovation. For charging pile assembly products, heat dissipation is one of the main factors affecting its performance. Therefore, thermal management that can well solve the heat dissipation during product operation will be one of the main directions of its transformation. In the context that forced air cooling cannot meet its high-power charging needs, liquid cooling has become the current mainstream development direction of the industry with higher heat dissipation efficiency, lower noise and safer and more stable performance.
In the current application of charging technology, since the current during charging is the charging cable and charging gun, the application of liquid cooling technology at the charging pile end is still for the cables and charging guns of the charging pile.
The liquid cooling system mainly includes four parts: liquid-cooled charging gun, liquid-cooled cable, coolant and liquid-cooled water pump. The principle is to arrange a special liquid cooling pipeline between the cable and the charging gun, and add common cooling media such as water, ethylene glycol aqueous solution, air conditioning refrigerant or silicone oil in the pipeline, and then drive the liquid cooling water pump to circulate the coolant in the pipeline to take away the heat, thereby achieving heat dissipation of the system.
Liquid-cooled charging guns and liquid-cooled cables are the second core components of liquid-cooled charging pile assemblies. Under the background of high-power charging requirements, the use of liquid cooling technology can greatly reduce the cross-sectional area of the charging cable while reducing its total weight, making the product more flexible and convenient. According to statistics, the weight of charging cables and charging guns under liquid-cooled charging technology is 40%-50% lighter than that of traditional technology. At the same time, due to the precise control of thermal management temperature, the stability of the charging current is improved. While meeting the high-current charging under high-power requirements, it can also ensure that the temperature rise of the system does not exceed the standard, thereby improving the safety of the equipment.
With the deepening of the promotion of fast charging technology in the automotive industry, the criticality of charging pile liquid cooling technology will be further highlighted, and the value of liquid-cooled charging guns and cables, which account for about 20% of the cost, may be further improved.
As we all know, the installation and use environment of charging piles often encounter some extreme factors. In the application of liquid cooling system, coolant is the key. Once the coolant leaks, it will cause system failure at the least and safety accidents at the worst. Therefore, for safety reasons, the requirements for charging piles using liquid cooling technology in terms of IP level, corrosion resistance, high and low temperature resistance, etc. are higher than those of traditional air cooling.
In addition, as the core of the charging pile, the charging module currently has an independent heat dissipation system and mainly dissipates heat through air cooling. However, driven by fast charging technology and system integration, the use of liquid cooling technology can isolate the charging module from environmental dust, flammable and explosive gases and other impurities through a fully enclosed design, making it safer and better, thereby improving the efficiency and life of the product.
In analogy with the development of thermal management of the whole vehicle, the current liquid cooling charging technology is mainly used in charging guns and charging cables. With the popularization of the application of liquid cooling technology for charging modules, it is not impossible to integrate the thermal management systems of the two regions and use software strategies to more accurately and reasonably control the entire charging pile system to improve the utilization rate of system energy.
In summary, under the trend of promoting fast charging in the automotive industry, in addition to the changes in related vehicle-side technologies, the development direction of the thermal management system of charging piles as infrastructure will inevitably change towards higher reliability and higher efficiency, and liquid cooling may be a good choice now and in the long term in the future.
