Many of these models use battery cells from major manufacturers. In fact, battery cells are to electric vehicles what bricks are to a building. The quality of a building is not solely determined by the bricks; the overall design and construction are extremely important. The same applies to electric vehicles; simply purchasing battery cells from a particular brand does not guarantee a worry-free experience.
Power batteries are a complex system engineering project. Cell quality, assembly technology, management technology, temperature control technology, and manufacturing processes are all important factors affecting battery stability and lifespan. Thermal management technology, in particular, has a significant impact on the user experience. Different thermal management solutions will yield drastically different results. Below, we will introduce common battery pack thermal management solutions.
I. Four common cooling methods
1. Natural cooling
Natural cooling utilizes natural air convection for heat exchange; simply put, it relies on natural wind. This is a basic heat dissipation solution, with advantages such as simple structure, low cost, and small footprint. However, its disadvantages are also obvious: low heat dissipation efficiency, inability to meet the cooling requirements of high-power charging and discharging. It is generally used in two-wheeled electric motorcycles with mild operating conditions and high cost sensitivity, as well as some low-end cars.
2. Forced air cooling
Forced air cooling uses a fan to draw air into the battery pack, forcing cool air to flow over the surface of the cells before expelling it, thus carrying the heat generated by the cells to the outside. To put it simply, compared to natural cooling, forced air cooling actively creates airflow, no longer relying on external airflow, making it more efficient and better suited for high-power charging and discharging. However, while forced air cooling significantly improves heat dissipation efficiency compared to natural cooling, it is still far inferior to liquid cooling. Furthermore, the need for air inlets and outlets in the air cooling system makes it difficult to achieve a high level of battery system sealing.
3. Liquid cooling
Liquid cooling primarily cools the battery system using a coolant. First, condensers, compressors, and other equipment force-cool the coolant. The low-temperature coolant flows through the battery system, exchanging heat with the cells, and then flows back to the heat exchanger to exchange heat with the low-temperature refrigerant, thus removing the heat generated by the battery from the system. Liquid cooling is more efficient than air cooling, meeting the heat dissipation requirements of high-power charging and discharging. It also provides more uniform heat dissipation and smaller temperature differences between cells, significantly enhancing battery system stability and extending its lifespan. However, liquid cooling systems consume some energy during operation and are slightly more expensive than air-cooled systems.
4. Direct cooling
Direct cooling systems are structurally similar to liquid cooling systems, but they directly inject the refrigerant from the car's air conditioning system into the battery pack. The low-temperature refrigerant can more quickly remove heat from the battery, resulting in higher heat dissipation efficiency. However, direct cooling systems also have weaknesses: firstly, they require high airtightness, placing higher demands on manufacturing processes; secondly, the heat dissipation uniformity of direct cooling systems is difficult to control, posing a risk of excessive temperature differences between battery cells.
Most importantly, direct cooling systems cannot integrate heating functions and require the installation of a separate heating system (usually a heating film or PTC component) to cope with low winter temperatures.
Of the above solutions, only the liquid cooling system can utilize the existing structure to achieve cooling in summer and heating in winter, while ensuring a high level of sealing for the battery system, thereby enabling the battery to quickly regain its activity.
Overall, liquid cooling solutions can effectively address the issues of heat dissipation and temperature rise in battery packs, thereby ensuring the stability of high-power charging and discharging. They are also relatively easy to implement in manufacturing processes, achieving a relatively ideal balance between performance and cost.
The mass-produced electric sports car, the Qiantu K50, employs a liquid cooling solution to ensure the stability of the battery system under high-power output. The Qiantu K50's battery system is supplied by Huatai Electric, a subsidiary of Great Wall Motors' Huaguan division, a supplier specializing in key components for new energy vehicles. Huatai Electric is undoubtedly one of the most capable manufacturers in overall electric vehicle solutions, especially in liquid-cooled thermal management systems.
II. Huatai Electric: Liquid Cooling Solution Experts
1. Modular design
The standard battery box developed by Huatai Electric measures 710*275*200mm, weighs 56kg, and has a total energy of 7.88kWh. Based on a modular design concept, the standard battery box can be freely combined into power battery packs of different shapes, capacities, and voltages to adapt to different vehicle models. Once higher energy density battery cells become available, OEMs only need to order upgraded standard boxes to quickly launch models with longer ranges, without needing to modify the vehicle structure or battery pack components, saving time and costs associated with upgrades.
2. Liquid cooling solution to cope with severe cold in winter and summer.
The standard battery pack from Walt Electric employs a liquid cooling system, integrating two heat exchange methods: weak cooling and strong cooling. When the battery pack temperature is below 45°C, a radiator is used for cooling, saving system energy. When the temperature is above 45°C, a compressor is used for rapid heat dissipation, ensuring the battery system can operate stably and continuously for extended periods within the range of -40°C to 60°C.
As mentioned earlier, air cooling has low efficiency and poor sealing reliability, while direct cooling is a single-cooling system and cannot simultaneously heat the battery. In contrast, Huatai Electric's liquid cooling structure can not only dissipate heat but also heat the battery.
In winter, the low temperature affects battery activity, significantly impacting charging and discharging capabilities. Huatai Electric's liquid cooling system ensures normal battery charging in extremely cold conditions (-30℃) and normal battery discharge in low-temperature environments, achieving zero power loss in the vehicle.
Furthermore, liquid cooling can raise the battery temperature by up to 0.6℃/min, while heating films and PTC methods only raise it by a maximum of 0.3℃/min. Not only is there a difference in heating speed, but Huatai Electric's liquid cooling solution also provides more uniform heating, controlling the cell temperature difference to within 5℃, while heating films and PTC methods have relatively poor heating uniformity, with cell temperature differences around 8-10℃.
Excessive temperature differences between individual battery cells can cause uneven electrochemical reaction rates within the cells, ultimately leading to variations in cell lifespan, capacity, and internal resistance, thus affecting the performance and lifespan of the battery pack. Walt Electric's thermal management solution can achieve smaller temperature differences, which translates to longer battery life and a lower repair rate.
When the liquid cooling system is working, it heats or cools the coolant, which consumes a certain amount of energy. Therefore, Huatai Electric has put a lot of effort into the insulation of the battery box. By using SMC shell, mica sheets, and insulation foam to create an insulating environment, the battery is completely sealed in an insulating environment to minimize the impact of the external environment on the battery temperature, thereby ensuring the ultra-low energy consumption of the thermal management system itself.
To put it more vividly, Walt Electric has built a house for its battery cells with excellent insulation, making the house's "air conditioning" very energy-efficient. This means lower overall vehicle energy consumption, allowing more electricity to be used to power the vehicle, thus improving driving range and user experience.
In summary, a battery pack is a complex system engineering project, not simply a collection of individual components, and requires a high level of design and manufacturing experience from the manufacturer. Walt Electric's products have been successfully applied in the high-power electric sports car K50, proving their ability to continuously charge and discharge at high power with stable performance, further demonstrating the superior quality of their thermal management system.
As consumers gain a deeper understanding of electric vehicles, battery packs with excellent liquid-cooled thermal management systems are becoming an increasingly essential option for high-quality electric vehicles. Walt, with its complete solutions, may well emerge as a winner in this new era.
