Significance of Battery Thermal Management System
A battery thermal management system is a system designed to control the temperature of the battery. With the rapid development of electric vehicles and new energy vehicles, batteries have become an indispensable part of vehicles. However, batteries are prone to overheating and overcooling during use, which in turn affects battery performance, life, and even safety.
Therefore, the role of the battery thermal management system is to regulate the battery temperature promptly and maintain the battery in a good working temperature range. People’s requirements for electric vehicle range, and charging time are getting higher and higher, effective battery thermal management system is important for improving the overall performance of the battery pack.
Characteristics Of Battery Thermal Management System
Battery thermal management system is mainly divided into active and passive two kinds. Active btms battery thermal management system is through the control of the cooling/heating system to adjust the battery temperature in time, a commonly used control system for PWM (pulse width modulation) system. A passive thermal management system is through the design of a reasonable structure, such as improving the heat sink wiring, increasing the heat sink, etc. to improve the battery heat dissipation capacity, to achieve the purpose of thermal management.
In addition, the battery thermal management system can also be divided into adjustable and non-adjustable. Adjustable battery thermal management system by the vehicle control unit for real-time monitoring and control of the battery temperature, at the same time will be based on vehicle speed, load, and other factors for intelligent adjustment. The non-adjustable battery thermal management system controls the battery temperature through pre-designed control logic and cannot be dynamically adjusted.
Each thermal management of electric vehicle battery systems has its characteristics and advantages, and the liquid thermal management system is currently the mainstream in the international arena.
Typical Analysis – Tesla
Tesla uses cylindrical batteries that have a small contact surface, making heat dissipation a challenging task. These single cells have a small capacity, so Tesla uses a high number of single cells in the battery pack, which increases the difficulty of maintaining battery temperature consistency. Therefore, Tesla has put a lot of effort into designing a thermal management system, and some of these design ideas can be seen in publicly available patents.
Tesla has developed a unique snake-shaped heat sink design. The curvature of each heat sink matches the cylindrical shape of the component, allowing for a larger contact area of about half a circle. This enhances the thermal conductivity between the electric core and the outside environment while reducing thermal resistance. Additionally, each metal sheet connects to the main heat sink channels on both the left and right sides.
Tesla uses a cooling method similar to the “two-way cooling” technique. This method involves reversing the direction of the left and right cooling channels. The left side flows up from the bottom while the right side flows down from the top. This design prevents uneven temperatures between the top and bottom of the system.
The cooling pipes are divided into four orifices. To prevent the coolant temperature from gradually increasing during the flow, which could lead to poor heat dissipation at the end, the thermal management system uses a two-way flow design. The two ends of the cooling pipes serve as both the inlet and outlet ports.
The space between the batteries and the cooling pipes is filled with a thermally conductive but electrically insulating material like Stycast 2850ct. This material serves three purposes:
1. It changes the contact form between batteries and cooling pipes from line contact to surface contact, which helps to increase heat transfer efficiency.
2. It promotes heat exchange between batteries, which helps to improve temperature uniformity between single batteries (in other words, it acts as passive thermal equalization).
3. It increases the overall heat capacity of the battery pack, which reduces the overall average temperature rise.
The battery is bonded to the shell, which is made of a combination of plastic parts and aluminum sheet metal parts (thickness 0.35mm) (plastic riveted), the structure of the aluminum plate facilitates the transfer of heat from the battery to the edges, making it easy to achieve heat dissipation of the module, and the plastic parts are used for insulation as well as being jammed into each other to form a battery cell
Compared to the aggressive Tesla, GM’s Volt uses a more robust square cell that also puts a lot of effort into thermal management. Since the contact surface of the square cells is relatively large, GM added a thermal ratchet directly between each two cells, through which the heat is transferred to the cooling circuit below.
Probably because the effect of the thermal ratchet is larger than that of the Tesla’s serpentine contact surface and less thermal resistance, GM did not design a two-way flow to control the temperature difference, which may also be related to the fact that the Volt’s battery pack does not have so many monomers, and the overall balance is better.
Summarize
Different battery thermal management programs are to increase heat dissipation efficiency by increasing heat dissipation channels. By using high thermal conductivity media, the rate of thermal conductivity is increased. Thermal conductivity and heat dissipation through active cooling.
However, different battery thermal management solutions will have certain differences due to the use of different thermal conductive media, heat dissipation paths and channels, heat dissipation area and effective heat dissipation area ratios, cooling media, cold plate arrangement, and heat sink effects.
TKT EV Solution is an experienced manufacturer of battery thermal management systems. We have close cooperation with the top 500 global automotive companies. We are happy to be your excellent partner. Feel free to contact us for any ideas and suggestions about battery thermal management systems. We will reply to you promptly.
