14250 battery

Brief Analysis of 14250 battery Thermal Management System

Tesla has caught fire again. In Tianhe District, Guangzhou, a Tesla Model S caught fire and suffered serious damage to the vehicle. This was less than two months after the last Tesla Model S caught fire after a collision in the United States.

Tesla has caught fire more than once or twice, and each time it has caused a great sensation, but the result is often inconclusive. Tesla has not announced the cause of the car's spontaneous combustion.

In fact, people are not only concerned about Tesla's spontaneous combustion problem, but more about the safety of new energy vehicles. After all, Tesla is a banner in the new energy vehicle market. If Tesla's products are not trustworthy, consumers will naturally have concerns when facing new energy vehicles.

The safety of new energy vehicles has always received great attention, and everyone's focus is also related to batteries, including fire and explosion, leakage, wading, radiation, etc. In fact, car companies will take these issues into consideration when developing new energy vehicles, and will solve the problems or make compromises in some aspects for safety.

Here, we mainly understand the cooling system of power batteries. The cooling performance will directly affect the efficiency of the battery, and will also affect the battery life and safety of use.

During the charging and discharging process, the 14250 battery will generate a certain amount of heat, which will cause the temperature to rise. The temperature rise will affect many characteristic parameters of the battery, such as internal resistance, voltage, available capacity, discharge efficiency and battery life, etc.

In order to extend the service life of the 14250 battery as much as possible and obtain the maximum power, it is necessary to use the battery within the specified temperature range, which involves the cooling system of the 14250 battery.

At present, the thermal management of the 14250 battery system of new energy vehicles can be divided into four categories: natural cooling, air cooling, liquid cooling and direct cooling. Among them, natural cooling is a passive thermal management method, while air cooling, liquid cooling and direct current are active. The main difference between the three lies in the different heat exchange media.

Natural cooling

Natural cooling does not have additional devices for heat exchange. In layman's terms, it relies on natural wind. For example, BYD Qin, Tang and Tengshi, which use LFP batteries, all use natural cooling.

The advantages of natural cooling are simple structure, low cost, and small space occupation. The disadvantages are also obvious. The heat dissipation efficiency is low and it cannot meet the cooling requirements of high-power charging and discharging. It is generally only used for electric vehicles with mild operating conditions and cost sensitivity.

Air cooling

Among the new energy electric vehicles sold on the market, the proportion of air cooling is still relatively large. It is currently the most widely used heat dissipation technology in the power batteries of new energy vehicles.

Air cooling uses air as the heat exchange medium. The principle is to use the cooling fan to draw air from the inside of the car into the 14250 battery box to cool the 14250 battery and the control unit of the 14250 battery. Models such as Toyota Prius, Honda Insight, Camry Hybrid and Corolla Hybrid all use air-cooled battery cooling systems.

Compared with other technologies, air cooling technology is relatively simple, safe and convenient to maintain, and can achieve good heat dissipation performance at a low cost.

However, the disadvantages of air cooling technology are also very obvious, especially compared with liquid cooling technology. The heat exchange coefficient between it and the battery surface is low, the cooling and heating speed is still relatively slow, the temperature uniformity inside the battery box is not easy to control, and the sealing design of the battery box is difficult, and the dust and water resistance is poor. It has to be said that some electric vehicle fires are due to the poor thermal management performance of air cooling technology.

Liquid cooling

As the use environment has higher and higher requirements for power batteries, liquid cooling technology has gradually replaced air cooling technology and become the preferred choice of major car companies, especially in large and medium-sized pure electric vehicles. The utilization rate of liquid cooling systems is very high. In small pure electric vehicles and even plug-in hybrid vehicles, there are more and more new models using liquid cooling.

The principle of liquid cooling technology is to use the coolant inside the battery pack to take away the heat generated by the battery during work, so as to achieve the effect of lowering the battery temperature.

Simply put, the liquid cooling system technology passes a water pipe through the battery pack. When the battery needs to be cooled, cold water is passed into the water pipe to take away the heat and cool it down through the cold water, and when the temperature needs to be increased, hot water is passed into the water pipe.

The liquid cooling system has a better temperature control effect on the battery pack than the air cooling system. The liquid medium has a high heat transfer coefficient, large heat capacity and faster cooling speed.

It is understood that Tesla Model S, Emgrand EV, JAC IEV6E and others have adopted liquid cooling technology. It is worth mentioning that JAC IEV6E Sports Edition is the first micro pure electric vehicle in China to adopt liquid cooling technology. The liquid cooling battery temperature control system it is equipped with can control the battery temperature between 15-35℃, and can be used normally in an environment of -30-55℃.

Direct cooling

The last thing to say is the direct cooling system. The structure of the direct cooling system is similar to that of the liquid cooling system, but the direct cooling will directly inject the refrigerant of the car air conditioning system into the battery pack. The refrigerant can absorb a lot of heat during the gas-liquid phase change process, and take away the heat inside the battery more quickly, and the heat dissipation efficiency is higher.

Direct cooling uses refrigerant as the heat exchange medium, and the refrigerant can absorb a lot of heat in the process. Compared with liquid cooling, direct cooling can increase the heat exchange efficiency by more than three times, and take away the heat inside the battery system more quickly. The direct cooling solution is adopted in the BMW i3.

The direct cooling system improves the heat exchange efficiency, but it also has defects. It has high requirements for the air tightness of the system and puts forward higher requirements for the manufacturing process. In addition, the heat dissipation uniformity of the direct cooling system is not easy to control, and there is a risk of excessive temperature difference in the battery cell.

In addition, the direct cooling system can only integrate the heat dissipation function, but not the heating function. It is necessary to install an independent heating system to cope with the low temperature in winter.

In the early days of the development of new energy vehicles, the market was dominated by A00 and A0-class models. These models did not have high requirements for performance and were mostly used for commuting in cities. Moreover, due to cost constraints, natural cooling or air cooling was often used.

However, with the development of new energy vehicles and the further promotion of the market, the structure of the new energy vehicle market is gradually becoming mature, and the market share of A-class vehicles and above is gradually increasing. At the same time, higher requirements are put forward for cruising range, energy density, battery capacity and charging speed.

As battery energy density increases, battery safety issues should also be given special attention, because the negative impact after thermal runaway will be relatively large, and the liquid cooling system has good performance in heat exchange efficiency, temperature control and NVH, and may be more widely used.

The development of new energy vehicles has entered a white-hot stage, and the requirements for battery technology are getting higher and higher. The thermal management system can play a great role in the safety of the battery. Its rapid development can also make new energy vehicles in a better progress.

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