Four Cooling Technologies for Battery Thermal Management Systems

As an indispensable product in our lives, lithium-ion batteries are found in everything from mobile phones to computers to electric vehicles. Compared with the chips that generate the most heat in electronic products, the heating component of electric vehicles is the power battery. Therefore, research on power battery thermal management technology is one of the most crucial projects for battery manufacturers and car companies.

The most primitive way of heat dissipation technology is air heat dissipation, and air heat dissipation is divided into two types: active heat dissipation and passive heat dissipation. Regardless of the form of heat dissipation, it uses air to remove heat. Passive heat dissipation is relatively simple. It mainly provides air inlets, ventilation routes and air outlets. When the vehicle is driving, the air contacts the battery to take away heat.

However, the biggest disadvantage of passive heat dissipation is that the heat dissipation efficiency is insufficient. Once the battery input/output power increases, resulting in increased heat generation, the heat dissipation effect is minimal. Another example is how to dissipate heat when the vehicle is not running when charging? Therefore, active heat dissipation increases air flow through fans and other equipment to enhance air flow and improve heat dissipation.

What is better than air heat dissipation is liquid cooling technology. The power battery is heat exchanged through coolant pipes distributed inside or on the battery surface, making heat dissipation more efficient. Liquid cooling dissipates heat by placing coolant pipes or cooling plates (with coolant inside) directly inside the power battery, and then flowing the coolant through relevant components to take away the heat inside the battery.

However, the key to liquid cooling heat dissipation is also a point that directly affects the heat dissipation effect of the power battery. It lies in the design and laying of the coolant pipeline and the direction of the coolant flow. Only by forming a reasonable return path and achieving uniform heat dissipation can the overall heat dissipation of the power battery be ensured. Keep the te mperature at a uniform level, and there will be no part of the temperature that is too low and part of the temperature that is too high, which will affect the health of the battery. For example, the power batteries of many new energy vehicles, including Tesla, use serpentine cooling pipes inside the battery pack, which can effectively increase the contact area between the cooling pipe and the battery to improve the heat dissipation effect.

In recent years, there has been an emerging passive heat dissipation method - phase change material heat dissipation technology. Phase change material is a cooling material that can absorb or release a large amount of heat when a phase change occurs, and can maintain constant temperature control of the surrounding temperature. The most common phase change material in our lives is water. When the temperature is as low as 0°C, water changes from liquid to solid (freezing releases heat); when the temperature is higher than 0°C, water changes from solid to liquid. (Dissolution is endothermic).

Based on the principle of phase change heat absorption, phase change materials can be used in lithium battery packs to achieve cooling. However, the phase change material itself is only a heat storage or heat absorption substance and cannot dissipate heat from any substance. Therefore, it needs to be added Some materials improve thermal conductivity and dissipate the heat absorbed by the phase change material through other methods such as air cooling and liquid cooling. In other words, phase change material heat dissipation technology can actually play an auxiliary role in air cooling or liquid cooling technology to maximize the heat dissipation effect.

In addition to the above three heat dissipation methods, there is also an active cooling technology - thermoelectric cooling, an energy conversion technology that uses the Peltier effect of semiconductor materials to achieve cooling or heating. When a DC power supply is connected, the heat at one end of the thermoelectric cooling device will be absorbed and the temperature will decrease, while the temperature at the other end will increase at the same time. In addition, this phenomenon is completely reversible. As long as the direction of the current is changed, the heat can be directed in the opposite direction. direction shift. Thermoelectric cooling technology has obvious advantages: no refrigerant, low energy consumption, and low noise. However, if used alone, the cooling efficiency is not high. When used on power batteries, it needs to be combined with other cooling technologies to achieve maximum effect.

Currently, many companies develop power battery thermal management systems based on thermoelectric cooling technology. They use composite phase change materials and thermoelectric semiconductor chips to embed the thermoelectric semiconductor chips on the side of the battery box, and the composite phase change materials are embedded in the square monomer. between batteries to solve the problem of uniformity and rapid cooling of single cells in the battery thermal management system.

Air cooling technology, as the most classic technology, is currently unable to meet the cooling needs of power batteries and has been replaced by liquid cooling technology. Liquid cooling has become the most mature and widely used cooling technology for power batteries. However, as battery heat, battery power, and charging speed increase, liquid cooling will gradually be unable to meet the battery's heat dissipation needs.

Therefore, the emerging phase-change material heat dissipation technology and thermoelectric cooling technology have great potential, but they need to be combined with other technologies to achieve the best results. At present, there is no absolutely high-quality heat dissipation technology. The future technology trend will be to combine multiple heat dissipation technologies to meet different heat dissipation needs.