The power battery system is typically composed of several key components, including the battery module, battery management system (BMS), thermal management system, and various electrical and mechanical systems. Several factors influence the large-scale adoption of new energy vehicles, such as battery system cost, driving range, and safety. As new energy vehicle technology continues to evolve, safety has become a central concern. Power lithium-ion batteries are particularly susceptible to thermal runaway due to exothermic reactions under conditions like overcharging, puncture, or collision, which can lead to smoke, fire, or even explosions. Additionally, the performance of power batteries—such as energy density and cycle life—is highly sensitive to temperature fluctuations, making thermal management an essential aspect of battery design.
First, the importance of thermal management
Under different driving conditions, individual battery cells generate heat due to internal resistance when delivering electric energy. This heat can raise the cell’s temperature beyond its normal operating range, negatively affecting battery performance and lifespan. The power battery system in an electric vehicle consists of multiple battery cells, and during operation, a significant amount of heat is generated within the compact battery box. If this heat is not efficiently dissipated, it can lead to overheating, reduced battery life, or even thermal runaway, posing serious safety risks.
Currently, domestic research on thermal management tends to focus on heat dissipation at the system and module levels, such as liquid cooling systems. However, there is less attention given to insulation measures at the cell level. From the design perspective, the structure of the battery cell and module must be considered when developing a thermal management system. Therefore, the overall design should take into account the temperature environment of each cell and the placement of modules. If cells are tightly packed without proper insulation or cooling, the temperature inside the battery pack can rise rapidly during charging and discharging, creating a major safety hazard.
Thus, it is crucial to study battery thermal management technologies that enhance both heating and cooling capabilities, ensuring the battery operates within an optimal temperature range and maintains a balanced temperature distribution within the battery box. Research should gradually expand from understanding the thermal runaway mechanism at the cell level to analyzing how thermal runaway propagates through the entire system.
Second, the difference between insulation and no insulation
Previous studies have shown that placing a thermal insulation layer between battery cells can block heat transfer from a failing cell to its neighbors. At the same time, the insulation layer is not fully sealed, allowing for convection channels that help dissipate heat from the affected cell across the entire battery pack, preventing localized overheating. In a study titled “Integration Study on Thermal Protection and Heat Dissipation of Vehicle Power Battery,†four schemes were analyzed for their thermal performance during thermal runaway. Scheme 1 involved no insulation or cooling between cells, while Scheme 2 used an insulating board, Scheme 3 employed heat pipes, and Scheme 4 combined both.
The analysis showed that Scheme 2 had excellent thermal resistance, effectively delaying thermal runaway propagation, but poor heat dissipation. Insulation alone couldn't meet the thermal management needs of the battery pack. Scheme 3 had good heat dissipation but experienced a sharp increase in temperature differences as discharge rates increased. After thermal runaway, its thermal resistance was much lower than Schemes 2 and 4. Scheme 4, however, significantly improved heat dissipation and temperature uniformity while maintaining high insulation performance, effectively blocking thermal runaway spread.
By increasing the thickness of the insulation layer and enhancing heat dissipation, thermal runaway propagation can be effectively controlled. Increasing the insulation thickness from 1mm to 2mm allowed the system to block thermal runaway before the heat pipe failed, ensuring normal operation. Combining appropriate insulation with cooling methods not only improves the stability of the battery pack's operating temperature but also effectively prevents thermal runaway.
A notable example is the thermal management system in the General Motors Volt, which uses liquid cooling. A thin metal heat sink (1mm thick) is placed between cells, with capillary structures allowing coolant to flow and remove heat. The insulation solution involves using foam between the cells.
Third, the application of foam
Battery systems are generally designed according to the shape of the battery core, which can be cylindrical, square, or soft-pack. Soft-pack batteries offer higher energy density, making them increasingly popular under energy subsidy policies. Their advantages include minimal external influence on the core, excellent performance, and lighter packaging materials. However, they also have disadvantages, such as more complex sealing and lower reliability. The aluminum-plastic film used in soft-pack batteries has low mechanical strength, and its lifespan limits the battery's service life.
To address issues like bulging during charge and discharge, foam is often used between soft-pack cells. It serves four main purposes:
1. Low hardness and high resilience allow it to absorb bulging stress and act as a buffer.
2. When a cell experiences uncontrolled heat, the foam acts as an insulator, slowing down heat diffusion and reducing accident risk.
3. Flame-retardant properties can delay fire spread, giving more time for escape.
4. Excellent resilience and compression ratio make it ideal for positioning.
Common foams used include PU, CR, EVA, and PE. However, in practical applications, only foams like PU that maintain sufficient elasticity under long-term compression are suitable for use between soft-pack batteries. Other foams, like CR, may lose their ability to recover after prolonged compression, leading to structural instability.
Additionally, upon disassembling the VOLT module, it was observed that the applied foam did not self-extinguish during fire tests, meaning it didn’t meet the national standard V0 requirement. This could be due to its strong insulation properties, which complement the liquid cooling system and prevent thermal runaway. Even if thermal runaway occurs, the foam might not play a significant role in flame retardancy, but its insulation function remains critical. Overall, the foam performs well in its intended role.
Flat Twin Cables
they are suitable for power & lighting circuits and building wiring. Also suitable for use as an earth wire the internal wiring of appliances and apparatus.
- Standard applied: BS 6004
- U0/U: 300/500V
- Certification: Third party test reports available
- Flame retardant or fire resistance or Low smoking and Halogen free or other property can be available
Flat Twin Cables,Flat Twin Wires,Outdoor Electrical Cable Types,Twin Flat Flexible Cable
Shenzhen Bendakang Cables Holding Co., Ltd , https://www.bdkcables.com