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The power battery serves as the energy source for electric vehicles. During charging and discharging, the battery generates heat, leading to a rise in temperature. This temperature increase can significantly impact various operational characteristics of the battery, such as internal resistance, voltage, state of charge (SOC), available capacity, charge and discharge efficiency, and overall battery life. Proper thermal management is essential to ensure optimal performance and longevity of the battery, which directly affects the vehicle's range and reliability.
**Table of Contents:**
1. Necessity of Power Battery Thermal Management
2. Classification and Introduction of Thermal Management Systems
3. Thermal Management System Design Process
4. Key Technologies in the Design Process
5. Performance Evaluation of Thermal Management Systems
The thermal effects on batteries also influence the performance and cycle life of the vehicle. Therefore, effective thermal management is crucial for enhancing battery performance, extending its lifespan, and improving the vehicle’s overall mileage.
Let’s explore this topic from several angles: battery thermal management systems, design flow, component types and selection, and system performance verification.
**01. Necessity of Power Battery Thermal Management**
1. **Heat Generation in Batteries**
Due to internal resistance and electrochemical reactions, batteries generate heat during both charging and discharging. This heat can cause temperature increases that negatively affect battery performance and safety.
2. **Impact of Temperature Rise on Battery Life**
Elevated temperatures reduce both calendar and cycle life. For example, a battery at 55°C may lose 80% of its capacity in just 272 days, while one at 23°C retains 80% after 6,238 days. A 32°C increase can reduce calendar life by over 95%. Similarly, higher temperatures can cut cycle life by nearly 50%, highlighting the importance of maintaining stable operating conditions.
To optimize battery performance, a well-designed thermal management system is necessary to keep each battery within a safe and efficient temperature range.
**02. Classification and Introduction of Thermal Management Systems**
There are five main types of thermal management systems, each with unique advantages and limitations:
1. **Direct Cooling System**
Compact and efficient, but lacks heating capabilities and condensate protection. Refrigerant control can be challenging, and system lifespan is shorter.
2. **Low-Temperature Radiator Cooling System**
Simple and cost-effective, especially in cold environments. However, it has limited cooling performance and is less effective in high-temperature conditions.
3. **Direct Water Cooling System**
Offers good cooling performance and wide application, but is more complex and consumes more energy than other systems.
4. **Air-Water Hybrid Cooling System**
Combines air and water cooling for better efficiency. It is compact and energy-efficient in low temperatures, but more complex and costly to implement.
5. **Direct Air Cooling System**
Uses ambient air to cool the battery. It is simple and low-cost, but not suitable for all cell types and can lead to contamination or slow recovery after exposure.
**03. Thermal Management System Design Process**
The development of a thermal management system should align with the overall battery pack design. The process typically includes multiple stages, from initial design to final product testing. Key steps involve modeling, simulation, component selection, and performance validation.
**04. Key Technologies in the Design Process**
1. **Determine Optimal Operating Temperature Range**
Different battery chemistries have different ideal temperature ranges. Lead-acid batteries operate best between 35–40°C, nickel-hydrogen batteries between 0–40°C, and lithium-ion batteries between -20–75°C.
2. **Thermal Field Calculation and Temperature Prediction**
Mathematical models help predict internal battery temperatures, ensuring accurate thermal management. Equations involving density, specific heat, and thermal conductivity are used to calculate heat distribution.
3. **Heat Generation Rate**
Heat generation occurs in two phases: during normal charging and during overcharge. Internal resistance plays a key role in determining how much heat is produced.
4. **Heat Dissipation Structure Design**
Proper arrangement of battery modules and cooling channels ensures even temperature distribution. Air-cooling methods like serial and parallel ventilation can be optimized for better airflow.
5. **Fan and Temperature Sensor Selection**
Choosing the right fan type and sensor placement is critical for effective cooling and accurate temperature monitoring. Fans must balance airflow, noise, and power consumption.
**05. Thermal Management System Performance Evaluation**
Simulation tools like FloEFD and Flowmaster are widely used to evaluate thermal management systems. These tools help analyze pressure drop, flow consistency, and thermal performance. Real-world case studies, such as those involving hybrid vehicles, demonstrate the effectiveness of these simulations in optimizing battery cooling and heating systems.
In conclusion, battery temperature directly impacts safety and performance. A well-designed thermal management system is vital for ensuring battery reliability and longevity. By following a structured design process, selecting appropriate components, and conducting thorough performance evaluations, engineers can enhance both the functionality and safety of electric vehicles.
September 27, 2025