Table of Contents
1.Why Do Battery Packs Need Cooling Plates
2.Classification and Application of Liquid Cold Plates
3.Welding Processes of Cooling Plates
4.Liquid Cooling Plate Design
5.Key Factors in EV Battery Cooling Plate Selection
6.Cleaning and Air Tightness Testing Before Delivery of Cold Plate
7.Conclusion
As electric vehicles gradually move toward high-power fast charging (800V platform), ultra-high energy density (such as the Kirin battery 255Wh/kg), and high integration (CTC/CTB technology), the capacity of energy storage systems is also increasing. Liquid cooling technology has already become a “must-have configuration” for battery packs.
What types of liquid cooling plates are there as key components of the liquid cooling system?
What types of cooling plates are applied in prismatic, cylindrical, and pouch cell modules?
01 Why Do Battery Packs Need Cooling Plates?
During charging and discharging, power batteries or energy storage batteries generate a large amount of heat (more severe during fast charging). If it cannot be removed in time, it may cause thermal runaway, leading to fire or explosion.
The optimal operating temperature for lithium-ion batteries is 25–40℃. Exceeding this temperature range not only significantly shortens battery cycle life but also greatly increases safety risks at extreme temperatures.
Compared with air cooling solutions, liquid cooling can achieve a heat dissipation density of 5–10 W/cm², which is about 5–10 times that of air cooling, greatly improving the heat dissipation performance of high energy density battery packs.
Comparison Table:
| Comparison Dimension |
Air Cooling |
Liquid Cooling |
| Heat Dissipation Efficiency |
Low (only 0.5–2 W/cm²) |
High (5–10 W/cm², 5–10 times that of air cooling) |
| Temperature Control Accuracy |
±5℃ or more (greatly affected by ambient temperature) |
Within ±2℃ (precisely controlled) |
| Applicable Scenario |
Low-power (range ≤300km), low-integration battery packs |
High-power (fast charging/high energy density), CTP/CTC technology |
| Volume and Weight |
Requires large ventilation space, increases vehicle weight |
Flow channels are thin (≤3mm), high integration, lightweight |
In summer: the heat dissipation density of air cooling is low, and battery temperature may reach over 50℃, forcing the charging power to decrease and extending charging time.
In winter: air cooling cannot actively heat the battery. The battery must consume extra energy to maintain temperature, leading to a significant reduction in driving range (20–30%).
Since 2020, liquid cooling technology has been gradually applied widely in battery packs. At present, liquid cooling has basically replaced air cooling. With continuous technological advancement, immersion liquid cooling and phase change material cooling will further enhance the performance of battery pack thermal management systems in the future.
02 Classification and Application of Liquid Cold Plates
1.1 Classified by welding process:
Friction stir welding: Requires advanced technology; design is flexible, performance is good, reliability is high, load capacity is good; cost is higher and weight is heavy.
Flat-tube cooling plate: Low technological threshold, simple processing, low cost, suitable for mass production.
Stamped cooling plate: Higher technological threshold, more flexible design, better performance, high reliability.
Serpentine tube: Cooling liquid contacts more battery area, complex process, single application.
1.2 Main Manufacturing Processes of Cooling Plates
Extrusion Type:
Stamping Type:
Accordion Type:
1.3 Cooling Plate Applications in Battery Packs：
| Item |
Selection |
| Prismatic |
Apply module-level water cooling plate at the bottom of the battery (flow channels can be set in the die-cast battery case), e.g., friction stir welding plate / flat-tube plate / stamped plate |
| Cylindrical |
Serpentine tubes interlaced between cylindrical cells, each cell in contact with water pipe, e.g., serpentine tube |
| Pouch |
Small water cooling plates integrated inside the module, aluminum plates integrated, e.g., stamped plate |
Cooling plates for power battery packs come in various forms. Different structures are suitable for different vehicle models and battery systems. There is no universal standard for the best cooling plate. Before finalizing the design, thermal simulations should be conducted for different structures to compare maximum temperature and temperature differences, selecting the optimal overall performance solution.
03 Welding Processes of Cooling Plates
There are three welding processes for cooling plates: brazing, friction stir welding, and fluxless brazing.
Brazing is widely used in traditional automotive radiator welding. It uses molten filler metal to wet the base material, fill the interface gap, and diffuse with the base material to connect the parts. Its advantage is that it can weld complex structures, and the parts can be made very thin.
Friction stir welding uses the relative movement and friction between the welding head and the workpiece end face to generate heat, making the ends reach a thermoplastic state to complete welding. This welding requires the parts themselves to have sufficient strength.
Fluxless brazing is developed based on brazing, allowing the welded parts to achieve minimal thickness and weight.
1.1 Material Selection:
Brazing cooling plate: AL-6063-t5
Friction stir welding cooling plate: AL-3003
1.2 Flow Channel Design Points:
The flow channels of cooling plates are mainly designed in two types: double-loop and single-loop. The differences and selection criteria are as follows:
Double-loop
Double-loop flow channel design illustration
The channels are arranged with minimal spacing under process constraints, with more circulation loops, allowing the battery to heat or cool more evenly with smaller temperature differences.
Single-loop
Single-loop flow channel design illustration
The channels are arranged with minimal spacing under process constraints, allowing the battery to heat or cool more evenly.
Selection Criteria: Regardless of the structure type, double-loop is preferred when layout space allows, because it allows simultaneous heating and cooling, reducing temperature differences.
1.4 Core Parameters
Flow resistance: The pressure difference meets the technical drawing requirements.
Thermal resistance: Meets heat dissipation requirements, ensuring battery temperature uniformity and temperature rise requirements.
Destruction pressure: Continuously pressurize the cooling plate until failure occurs. The cooling plate must withstand a maximum pressure ≥1MPa.
Airtightness: Meets airtight performance. Visually confirmed with no internal or external deformation, damage, or structural changes.
High and low temperature resistance: Meets airtightness requirements with no deformation or damage.
Vibration durability: No leakage, no mechanical damage after testing, and flatness maintains drawing specifications.
There are also requirements for joint welding strength and internal/external corrosion resistance.
The quality of thermal conductivity includes two aspects: one is that the cooling plate must have a high thermal conductivity coefficient, and the other is that it must ensure good temperature uniformity. Considering various materials, aluminum alloy is a better choice, with a thermal conductivity of 150-250 W/(m·K), low density, low cost, and good machinability. The cooling plate must also ensure that the temperature difference between cells in the same battery pack is ≤3℃. Therefore, multi-channel design can minimize temperature gradients between cells at different positions.
Cooling plates are usually located at the bottom of the battery casing and need to withstand compressive forces from the cells and liquid pressure from the coolant. Therefore, they must have sufficient strength to prevent thin-walled areas from failing under high pressure. For power battery packs, cooling plates also need vibration and impact resistance to prevent fatigue cracks caused by stress concentration. For energy storage packs, although the plates are stationary during operation, they must still withstand certain vibration and impact forces during transportation.
Extruded cooling plates are limited by the process, and their flow channels can only be designed as straight lines. Stamped cooling plates allow flexible channel design, improving heat flow density and heat exchange efficiency.
06 Pre-Delivery Cleaning and Airtightness Testing of Cooling Plates
Cooling plates are critical components of the battery pack’s liquid cooling system, and their cleanliness and airtightness are very important.
If the channels are not clean, coolant flow will be uneven, and large particles may block the flow, reducing heat transfer efficiency.Additionally, impurities may damage the oxide protective layer on the metal walls, causing corrosion of the cooling plate.
(1) Potential Contamination Points During Manufacturing
A. During cutting or trimming, oil, cutting coolant, and machining debris can easily enter the channels.
B. When cleaning tools with cutting fluid, metal fragments in the fluid can easily enter the cooling plate channels.
C. Non-linear channels have blind spots that are difficult to clean thoroughly.
(2) Cleaning and Protection of Cooling Plates
Use a high-pressure water gun to flush the internal channels of the cooling plate to remove residues, particles, or other impurities. After flushing, the plate assembly must be dried to ensure no moisture remains.
During handling, foreign particles can also enter the channels, so the inlet and outlet must be sealed in advance, e.g., with dust covers or rubber caps.
(3) Airtightness Testing of Cooling Plates
Leakage of cooling plates is a serious issue. It affects coolant flow, reduces heat dissipation, can corrode equipment, and may even cause short circuits or thermal runaway. Therefore, all cooling plates must be tested for airtightness before delivery.
Submerge the cooling plate in a water tank and observe for bubbles to judge airtightness. This method is simple but requires drying afterward and is rarely used in practice.
Key parameters: inflation pressure, inflation time, pressure stabilization time, and leakage rate.
An excellent cooling plate must not only provide sufficient heat dissipation but also have a reasonable structural design to ensure close contact with the battery, maximizing heat removal.With the rapid development of electric vehicles and energy storage devices, the market demand for cooling plates continues to grow. In the future, cooling plate technology is expected to become more advanced, designs more refined, and even new materials or intelligent solutions may be introduced to further improve heat dissipation and service life.It is important to recognize the significance of cooling plate design. It is not only key to maintaining stable battery temperature but also crucial for extending battery life and ensuring safe system operation.
