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中文01 Purpose of Condensation Test
Condensation occurs when water vapor in the ambient air condenses into droplets on the surface of internal battery pack components whose temperature falls below the dew point. If these droplets accumulate on low-voltage circuits, high-voltage circuits, or insulating materials, they can lead to serious safety hazards such as short circuits and insulation failures.
The condensation test primarily focuses on three objectives:
1. Proactive Prevention:
By simulating condensation conditions that the battery system may encounter during actual use, the test confirms whether condensation occurs in real-world scenarios. This helps identify potential condensation risks (such as insufficient sealing, uneven thermal management, or poor moisture resistance of materials) in advance.
2. Condensation Point Localization:
By placing sensors and moisture-indicating materials in key areas inside the battery pack, the test locates the specific points where condensation occurs. This analysis of condensation risks guides design optimizations (e.g., adding waterproofing measures, improving thermal management strategies) based on the test results.
3. Hazard Assessment:
By monitoring the patterns of temperature and humidity changes of critical components in a condensation-prone environment, the test assesses the tolerance, lifespan, and reliability of these components under such conditions.
02 Pre-Test Preparations
1. Test Conditions
– Ambient Temperature: (22 ± 5) °C
– Relative Humidity (RH): 10% to 90%
– Atmospheric Pressure: (86 to 106) kPa
2. Sample Requirements
* Open the battery pack and dry it in an environment of 50°C and relative humidity (RH) of 5%±2% for 48 hours to remove residual moisture inside the pack.
* Then, place it in an ambient temperature environment with a relative humidity (RH) of 85% for 48 hours to absorb moisture, simulating real-world moisture penetration.
* After sealing the battery pack, verify that the gas tightness of the battery system meets the requirements.
* If active dehumidification components are present, they must be operated until the dew point reaches a stable level (equilibrium) with no further downward trend; alternatively, operate the active dehumidification components normally for two weeks.
3. Monitoring Point Setup
Place moisture indicators and sensors in critical areas of the battery pack:
* Structural components
* Low-voltage circuits
* High-voltage circuits
* Battery cells/modules
* Thermal management components
* Battery Management System (BMS)
Place five temperature sensors (attached to the component surface) and five dew point sensors (directly below the corresponding temperature sensors) in each type of area mentioned. Simultaneously, place moisture indicators (e.g., humidity indicator cards that change color to visually reflect humidity changes) to monitor traces of condensation.
03 Test Procedure
1. Constant Damp Heat Test:
* Place the sample in an environment of 50°C and relative humidity (RH) of 93%±3% for 24h / 48h / 72h / 96h (optional).
* Monitor the insulation resistance via the BMS throughout the test. Terminate the test immediately if an insulation warning is triggered.
* After the test, allow the sample to return to ambient temperature. Then, perform checks for insulation withstand voltage, airtightness (leak rate ≤ manufacturer’s requirement), and functionality (e.g., BMS communication).
2. Constant Damp Heat Charge-Discharge Cycle Test:
* Maintain the temperature and humidity conditions specified above.
* Perform charge and discharge cycles according to the project’s required strategy. For example: charge to 80% SOC, then let it rest for 6-8 hours; discharge to 30% SOC, then let it rest for 6-8 hours. Repeat this cycle for 30 / 60 times, or for a total duration of 720h / 1440h (optional).
* Monitor insulation resistance and cell temperature during the process.
* After the cycling, repeat the insulation, airtightness, and functionality checks.
3. Cyclic Damp Heat Test:
* Perform 10 cycles (240 hours total) in an environment ranging from -10°C to 50°C with relative humidity (RH) of 93%±3%, as required by **GB/T 2423.34 Environmental testing – Part 2: Test methods – Test Z/AD: Composite temperature/humidity cyclic test**. This simulates severe temperature and humidity fluctuations.
After the test, let the sample rest at ambient temperature for 1 hour. Then, perform checks for insulation, airtightness, and functionality. Open the pack to inspect the state of the moisture indicators (e.g., water accumulation, color change) and the condition of various components.
