In the long run, new energy vehicles, especially pure electric vehicles, will continue to maintain their global growth momentum, with stricter emission requirements, more and more optimized battery technology and prices, continuous improvement in infrastructure, and consumer acceptance of electric vehicles. taller and taller.

The most valuable component in an electric car is the battery. For batteries, time is not a knife, but temperature is a knife. No matter how good the battery technology is, extreme temperatures are a problem. Therefore, the battery thermal management system came into being.

Regarding vocabulary such as ternary lithium and ternary electric system, we have already discussed the literacy class before, and today we are going to pull the battery thermal management system of electric vehicles. To this end, we consulted Mr. Lars Kostede, the project leader of the HELLA China implementing agency, who is an expert in this field.

What is a thermal management system?

Don’t be fooled by this word, it’s like a roadside mobile phone packaging, or, to put it mildly, “polymer finish.” “Thermal management system” is more like an all-encompassing term.

Different thermal management systems target different areas, such as the water tank of the engine, and the air conditioner on the car is the biggest factor in determining ride comfort-but they are not. Whenever the car’s air conditioner is stopped, no matter how strong the chassis filtering capacity is, how good is the NVH? A Rolls-Royce without air conditioner is not as good as a Chery—especially at this time of the year, air conditioners are vital to the lives of car owners. Important.

Electric vehicle battery thermal management system actually addresses this point.

Why do batteries need a thermal management system?

Compared with fuel vehicles, the “unique” safety risk of electric vehicles lies in the thermal control of the power battery. After thermal runaway occurs, chain diffusion similar to thermonuclear reaction occurs.

Take the famous 18650 lithium battery as an example. Many battery cells form a battery pack. If the heat of one battery cell is out of control, the heat will be transferred to the surroundings, and then the surrounding battery cells will have a chain reaction one after another like a firecracker. During this process, many research topics will be initiated, including intermediate temperature rise rates, chemical and electrical heat generation, heat transfer and convection.

The easiest and most effective way to control such a chain thermal runaway is to add an insulation layer between the power battery units-now many fuel vehicles pay attention to it, and a circle of insulation layer is placed on the outside of the battery.

Although the insulation layer is the simplest type of battery thermal management system, it is also the most troublesome one. On the one hand, the thickness of the insulation layer will directly affect the overall volume of the battery pack; on the other hand, the insulation layer is a “passive thermal management system” that slows down the battery pack when it needs to be heated or cooled.

The best working temperature of traditional lithium battery is 0℃~40℃. Excessive temperature will reduce the storage capacity of the battery and the cycle life of the battery. In fact, the ground temperature in summer is very likely to exceed 40°C, and everyone knows that the temperature of a closed car may exceed 60°C in summer. Similarly, the inside of the battery pack is also a confined space and it will be very hot… For electric vehicles, a complete battery thermal management system is very important.

A certain brand of electric vehicles sold on a large scale in North America in 2011, due to its relatively simple battery thermal management system, the battery capacity decayed severely after 5 years, resulting in North American car owners having to pay $5,000 to replace the battery.

And if the temperature is lower than 0°C, the discharge capacity of ordinary lithium batteries will be reduced-also known as “running”. Moreover, the lower the temperature, the worse the ionization activity of the battery, which will lead to a decrease in charging efficiency, that is, “difficult to charge and low capacity”. A good battery thermal management system will heat the battery pack before charging at a low temperature, and even has a low-energy insulation function when the power supply is connected.

In fact, some companies have developed low-temperature lithium batteries suitable for extreme environmental temperatures. For example, a low-temperature lithium battery designed for polar environments can achieve rapid charging at 0.2C at -40°C and a discharge capacity of not less than 80%. Others work well in the temperature range of -50°C to 70°C and do not require any help from a thermal management system.

These lithium batteries are difficult to meet the needs of auto companies in terms of energy density and cost, so for auto companies, battery thermal management systems are still an economic solution to ensure battery life and operating conditions.

How does the battery thermal management system work?

The working principle of the battery thermal management system is similar to that of a household air conditioner. Simply put, the measurement and control unit is responsible for temperature monitoring, and the temperature control component drives the heat transfer medium to complete the final temperature control. However, the temperature control accuracy of the battery thermal management system is much higher than that of household air conditioners, and it can even monitor the temperature of a single battery cell in a battery pack.

The common heat conduction media in the battery thermal management system are air, liquid and phase change materials. Due to efficiency and cost factors, most of the current mainstream battery thermal management systems use liquid as the heat transfer medium. The pump is the core component of this battery thermal management system.

At present, HELLA provides many core components for the battery thermal management system of new energy vehicles, the most representative of which is the electronic circulating water pump MPx, which can accurately control the pressure and flow of the The operating temperature is maintained at an ideal level to achieve the durability of the battery system.

In addition, HELLA’s battery thermal management system also provides a system solution for the automotive industry, not just a product solution, especially in China, which is very important…

So, what is a system solution, and what is a simple solution?

Buy a computer, for example, you tell the seller the performance, use, and affordable price, the seller helps you choose some products and tells you the warranty policy, fancy you, pay, and notify the seller that you want to install any version of the operating system , The next day on the computer, after you sign for something, the computer crashes directly to the merchant-this is called a system solution.

The only solution is to buy your own shell, CPU, fan, memory, hard drive, graphics card on the market, and then make one yourself. This process cannot be resolved within two days. And the assembled computer does not have a warranty. Once the machine fails, you need to go to the parts for maintenance one by one, and communicate with the relevant parts suppliers after finding the faulty parts. In addition, if a third-party accessory is damaged due to a malfunction of the accessory, for example, the CPU burns out due to a fan problem, it is best to pay the cost of the new fan by the fan supplier, and the loss of the CPU will not be compensated…

This is the difference between a system solution and a single solution.