High – Temperature and High – Humidity Testing of Power Battery Systems

1. Introduction

In the realm of new energy electric vehicles, power battery systems are the cornerstone of their operation. As the demand for electric vehicles continues to soar globally, ensuring the reliability and performance of these battery systems across diverse environmental conditions becomes of utmost importance. Among the various environmental factors, high – temperature and high – humidity conditions pose significant challenges to the stability and safety of power battery systems. This is why high – temperature and high – humidity testing has emerged as a critical assessment method in the development and quality control of power battery systems.

2. Test Objectives and Methods

2.1 Test Objectives

The primary objective of high – temperature and high – humidity testing is to comprehensively evaluate the performance and reliability of power battery systems when exposed to extreme hot and humid environmental conditions. This evaluation is crucial as electric vehicles are expected to operate in a wide range of climates, from the tropical regions with high humidity and elevated temperatures to the monsoon – affected areas. By subjecting the battery systems to such harsh conditions in a controlled testing environment, manufacturers can anticipate potential issues that may arise during real – world usage. This helps in improving the design, enhancing the durability, and ensuring the safety of the battery systems, ultimately leading to more reliable and long – lasting electric vehicles.

2.2 Test Methods

The testing process involves placing the power battery system inside a specialized climate – controlled chamber. This chamber is capable of precisely regulating both the temperature and humidity levels to mimic the target environmental conditions. For example, the temperature can be set to levels as high as 60°C or even higher, depending on the specific requirements of the test, while the relative humidity can be maintained at 90% or above.

During the test, a multitude of parameters related to the battery system are continuously monitored and recorded. These parameters include the temperature and humidity within the battery system itself, which are measured using internal sensors. The voltage across the battery cells is monitored to detect any abnormal changes that could indicate a degradation in performance. The current flowing in and out of the battery is also tracked, as it provides insights into the battery’s charging and discharging efficiency. Për më tepër, the battery’s capacity is measured periodically. This is often done by conducting a series of charge – discharge cycles before, during, and after the high – temperature and high – humidity exposure. By comparing the capacity values, the extent of capacity degradation due to the environmental stress can be accurately determined.

3. Impact of High – Temperature and High – Humidity on Battery Systems

3.1 Effects of High Temperature

High temperature has a profound impact on the internal physical and chemical processes within the battery system. Së pari, it accelerates the chemical reactions occurring at the electrodes. For instance, in lithium – ion batteries, the lithium – ion diffusion rate between the anode and cathode is increased at high temperatures. While this may initially seem beneficial as it can enhance the power output in the short term, over time, it leads to the degradation of the electrode materials. The increased reaction rate can cause the formation of a solid – electrolyte interphase (SEI) layer on the anode surface to grow more rapidly. This thicker SEI layer increases the internal resistance of the battery, resulting in a decrease in its overall capacity.

Për më tepër, high – temperature conditions can also cause thermal expansion within the battery components. Different materials used in the battery, such as the electrodes, separators, and current collectors, have different coefficients of thermal expansion. This mismatch in expansion can lead to mechanical stress and strain within the battery. Over time, this can cause the electrodes to delaminate from the current collectors, further deteriorating the battery’s performance and potentially leading to short – circuits.

3.2 Effects of High Humidity

High humidity poses a significant threat to the integrity of the battery system due to the ingress of moisture. Water molecules can penetrate the battery enclosure if it is not properly sealed. Once inside, the water can react with the electrolyte in the battery. In lithium – ion batteries, for example, the electrolyte contains lithium salts dissolved in organic solvents. Water can react with these salts, forming lithium hydroxide and other by – products. This chemical reaction not only changes the composition of the electrolyte but also reduces its conductivity, thereby decreasing the battery’s power – delivering capabilities.

Për më tepër, the presence of moisture can cause corrosion of the metal components within the battery, such as the current collectors and the electrode tabs. Corrosion weakens these components, increasing the risk of electrical connection failures. In extreme cases, the corrosion products can also contaminate the electrolyte, leading to further degradation of the battery’s performance. Për më tepër, the ingress of moisture can also affect the separator’s function. The separator is designed to prevent direct contact between the anode and cathode, but if it becomes wet, its insulating properties may be compromised, potentially leading to internal short – circuits and a significant safety hazard.

4. Evaluation Indicators in High – Temperature and High – Humidity Testing

4.1 Temperature Response and Humidity Response

Monitoring the temperature response of the battery system during high – temperature and high – humidity testing is essential to assess its thermal management capabilities. A well – designed battery system should be able to maintain its internal temperature within an acceptable range even when exposed to high – temperature external environments. This is often achieved through the use of cooling systems, such as liquid – cooled or air – cooled mechanisms. By analyzing the temperature response data, manufacturers can evaluate the effectiveness of these cooling systems. For example, if the internal temperature of the battery system rises rapidly and exceeds the recommended operating temperature range, it indicates that the cooling system may need improvement.

Similarly, the humidity response of the battery system is crucial for evaluating its moisture – protection capabilities. A reliable battery system should be able to prevent excessive moisture from entering its internal components. This can be achieved through proper sealing and the use of moisture – resistant materials. During the test, the humidity levels inside the battery system are monitored. If the internal humidity rises significantly above the ambient level, it suggests that the moisture – protection measures are insufficient, and there may be potential leakage points in the battery enclosure.

4.2 Capacity Attenuation and Internal Resistance Change

Capacity attenuation is one of the most critical indicators of a battery’s performance degradation. During high – temperature and high – humidity testing, the battery’s capacity is measured at regular intervals. A significant decrease in capacity over time indicates that the battery is suffering from irreversible damage due to the environmental stress. The capacity attenuation rate can be used to predict the battery’s lifespan under real – world high – temperature and high – humidity conditions.

Internal resistance change is another important parameter. An increase in internal resistance implies that the battery has more difficulty in delivering and accepting electrical current. This can lead to reduced power output during discharge and slower charging times. By measuring the internal resistance before, during, and after the test, manufacturers can understand how the battery’s internal structure and components are affected by high – temperature and high – humidity conditions. A sudden or significant increase in internal resistance may indicate severe damage to the battery, such as electrode degradation or electrolyte contamination.

4.3 Safety Performance

Safety is of paramount importance in power battery systems. High – temperature and high – humidity testing also focuses on evaluating the battery’s safety performance under these extreme conditions. This includes assessing the battery’s ability to prevent thermal runaway, which is a dangerous situation where the battery’s temperature rapidly escalates, leading to potential fire or explosion. The battery system should be equipped with safety mechanisms, such as thermal fuses and over – temperature protection circuits, to prevent thermal runaway.

Për më tepër, the test also examines the battery’s protection against over – discharge and over – charge conditions. Over – discharge can cause the battery cells to be damaged irreversibly, while over – charge can lead to gas generation and increased internal pressure. In a high – humidity environment, the risk of electrical short – circuits due to moisture – induced corrosion or component failure is also a major safety concern. Therefore, the safety performance evaluation in high – temperature and high – humidity testing aims to ensure that the battery system can operate safely even in the most challenging environmental conditions.

5. Test Implementation and Result Analysis

5.1 Test Implementation

The implementation of high – temperature and high – humidity testing requires strict control over the test environment. The climate – controlled chamber must be calibrated regularly to ensure accurate temperature and humidity settings. The battery system is installed in the chamber in a way that simulates its actual operating position in the vehicle. All the necessary sensors for monitoring the various parameters are properly connected and calibrated before the test begins.

During the test, the temperature and humidity levels are gradually increased to the target values and then maintained for a specified duration. This duration can vary depending on the test standards and the specific requirements of the battery system. For example, some tests may last for several days or even weeks to simulate long – term exposure to high – temperature and high – humidity conditions. The data collected during the test is recorded in real – time using a data acquisition system, which allows for continuous monitoring and analysis.

5.2 Result Analysis

Once the test is completed, the collected data is analyzed in detail. The analysis of the temperature and humidity response data can help identify any issues with the battery’s thermal management and moisture – protection systems. If the temperature control is ineffective, measures can be taken to improve the cooling system, such as optimizing the coolant flow rate or adding more heat – dissipating fins. If the humidity protection is insufficient, the battery enclosure can be redesigned to improve its sealing performance.

The analysis of capacity attenuation and internal resistance change data provides insights into the battery’s long – term performance and lifespan. By comparing the data with the initial values, manufacturers can determine the extent of degradation and develop strategies to mitigate it. For example, if the capacity attenuation is found to be excessive, new electrode materials or electrolyte formulations can be explored to improve the battery’s stability under high – temperature and high – humidity conditions.

The safety performance analysis is crucial for ensuring the reliability of the battery system. If any safety issues are detected, such as a potential risk of thermal runaway or over – discharge, the battery’s safety mechanisms can be enhanced. This may involve adding more advanced over – temperature sensors or improving the design of the over – charge protection circuit.

6. Conclusion

High – temperature and high – humidity testing plays a vital role in the development and quality assurance of power battery systems for new energy electric vehicles. By subjecting the battery systems to extreme environmental conditions, manufacturers can identify potential weaknesses and make improvements to enhance their performance, reliability, and safety. The comprehensive evaluation of temperature response, humidity response, capacity attenuation, internal resistance change, and safety performance provides valuable insights for the design and optimization of battery systems.

As the electric vehicle market continues to expand and electric vehicles are expected to operate in more diverse and challenging environments, the importance of high – temperature and high – humidity testing will only increase. It serves as a critical tool for ensuring that power battery systems can meet the stringent requirements of real – world usage, contributing to the widespread adoption and long – term success of new energy electric vehicles.