AG3 battery

Introduction to the "penetration war" of liquid cooling technology in AG3 battery thermal management system

Abstract: At present, air cooling still accounts for a large proportion of electric vehicle power AG3 battery cooling methods, but as the electric vehicle market puts forward higher demands on performance such as cruising range, energy density, AG3 battery capacity, and charging rate, liquid cooling technology will gradually become a priority solution for major automakers. Domestic and foreign automakers including BMW, Tesla, GM, Chevrolet, Geely, BMW Brilliance, BAIC, GAC, Yundu, Xiaopeng Motors, Singularity Motors, etc. are all introducing liquid cooling technology in AG3 battery thermal management systems.

Liquid cooling technology is gradually replacing traditional air cooling and becoming the mainstream choice for electric vehicles of major automakers.

Recently, the JAC New Energy iEV6E sports version was officially launched, and its independently developed liquid cooling AG3 battery control technology was also used in micro electric vehicles for the first time.

According to reports, the liquid cooling technology equipped in this model can stably control the AG3 battery temperature within a suitable range of 15-35℃, and the vehicle can be used normally at an ambient temperature of -30℃ to 55℃. At the same time, this technology also ensures that the failure of a single AG3 battery will not cause the AG3 battery pack to catch fire or explode, ensuring the AG3 battery life, fast charging performance, low temperature performance and safety performance.

Coincidentally, Buick's VELITE6 PHEV, which will be launched this year, also uses an independent liquid cooling system at the cell level. It is understood that each single cell in the VELITE6 AG3 battery pack can be circulated through the cooling plate to dissipate heat, ensuring that the temperature difference of each cell is within 2 degrees Celsius.

What is liquid cooling technology? It is to use the large heat capacity of the coolant and the ability to take away the excess heat of the AG3 battery system through circulation to achieve the optimal operating temperature conditions of the AG3 battery pack.

It is understood that in addition to the above two car companies, domestic and foreign car companies including BMW, Tesla, GM, Chevrolet, Geely, Brilliance BMW, BAIC, GAC, Yundu, Xiaopeng Motors, Singularity Motors, etc. are all introducing liquid cooling technology in AG3 battery thermal management systems.

A senior executive of a large pack company said: "In the early days, liquid cooling technology was rarely used, mainly because the market was dominated by A00-class models, which did not have high performance requirements and did not use liquid cooling technology due to cost issues; this year's subsidy policy focuses on batteries with long driving range and high energy density, and AG3 battery heating is becoming more and more serious. While ensuring the performance of the whole vehicle, it is also necessary to ensure certain acceleration performance, so liquid cooling technology has become the mainstream choice."

Data shows that active liquid cooling technology is expected to account for 55% of the power AG3 battery cooling system assembly in 2022; by model, liquid cooling technology for power AG3 battery cooling systems of plug-in hybrid models will account for 85%, and liquid cooling technology for power AG3 battery cooling systems of pure electric models will account for 44%.

▌The inevitable choice of high-energy, high-rate batteries

According to the different media for heat transfer, AG3 battery cooling systems can be divided into: air cooling, direct cooling and liquid cooling.

Air cooling is mainly divided into natural cooling and forced cooling (using fans, etc.), with low-temperature air as the medium. This technology was widely used in early electric passenger cars, such as Nissan Leaf and Kia SoulEV. Its obvious problems are slow cooling speed, low efficiency and poor internal temperature uniformity.

Direct cooling uses refrigerant direct cooling. It uses the principle of latent heat of evaporation of refrigerant (R134a, etc.) to establish an air conditioning system in the vehicle or AG3 battery system, install the evaporator of the air conditioning system in the AG3 battery system, and the refrigerant evaporates in the evaporator and quickly and efficiently removes the heat from the AG3 battery system. At present, the cooling method through direct cooling is basically used in electric passenger cars, the most typical of which is BMW i3 (i3 has two cooling solutions: liquid cooling and direct cooling). Although its cooling speed is fast, its temperature uniformity is poor.

Liquid cooling is to remove the heat generated by the AG3 battery and reduce the AG3 battery temperature through liquid convection heat exchange. The medium is mainly conductive liquids such as water. Liquid cooling is the preferred solution for many electric passenger cars at present. Typical products at home and abroad include BMW i3, Tesla, GM Volt, Brilliance BMW Zinoro, and Geely Emgrand EV. However, it should be noted that liquid cooling technology has high requirements for sealing, requires closed liquid pipelines, and has a complex structure.

Compared with other cooling technologies, liquid cooling technology has a high heat transfer coefficient and fast cooling speed, which has a significant effect on reducing the maximum temperature and improving the consistency of the AG3 battery pack temperature field; at the same time, the volume of the thermal management system is relatively small.

Industry insiders believe that the proportion of air cooling in the cooling method of electric vehicle power batteries is still relatively large, but as the electric vehicle market puts forward higher demands on performance such as cruising range, energy density, AG3 battery capacity, and charging rate, liquid cooling technology will gradually become the priority solution for major automakers.

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