WAFU
On-Board Charger (OBC) Airtightness Testing Solution
Why Airtightness Testing Is Essential for On-Board Chargers
The OBC (On-Board Charger) is a key component in new energy vehicles that converts AC to DC power. It is typically installed near the chassis, engine compartment, or battery pack and operates in complex environments. Airtightness testing is critical for the following reasons:
| Issue | Detailed Description |
|---|---|
| Prevent Water Short Circuit | In scenarios such as driving in the rain or high-pressure car washing, poor sealing may lead to water ingress, short circuits, and burnout. |
| Ensure Insulation Safety | Moisture infiltration can cause PCB breakdown and failure, affecting the entire vehicle's charging system. |
| Meet IP Protection Requirements | Most OBCs are required to meet IP67 / IP68 levels, which must be verified through airtightness testing. |
| Improve Vehicle Quality & Reliability | Sealing issues are one of the main causes of high after-sales repair rates and frequent customer complaints. |
Figure 1: Structural Diagram of the On-Board Charger
Case Alert
In 2023, some models of GAC Aion in the humid southern region frequently encountered "charging fault" issues. Failure analysis traced the cause to uneven glue application and aged sealing rings around the OBC housing, resulting in minor water ingress and corrosion of the control board. The manufacturer introduced high-precision airtightness testing equipment for 100% OBC housing and final product testing, reducing the defect rate from 1.8% to 0.2%, significantly improving customer satisfaction and vehicle delivery quality.
2. Detection Methods
Based on the structure and precision requirements of the OBC, the following airtightness testing technologies can be used:
| Method ID | Method Name | Detailed Description |
|---|---|---|
| 1 | Pressure Decay (Differential Pressure) |
Simple principle and low cost, suitable for early-stage testing of OBC housing. Often used in mid-line production to assess preliminary structural integrity. |
| 2 | Mass Flow Method |
Enables accurate flow measurement with high sensitivity and automation. Typically used in final inspection after full assembly. |
| 3 | Helium Leak Detection |
Extremely high precision (10⁻⁶ ~ 10⁻⁹ Pa·m³/s), ideal for military or high-end OBC waterproofing. Detects microscopic gaps, connectors, and glue-sealed areas. |
3. Testing Procedure (Using Mass Flow Method)
| Step | Procedure |
|---|---|
| 1 | Loading: OBC is placed into the sealing fixture via robotic arm or manually. |
| 2 | Sealing & Clamping: Fixture forms an airtight environment around the OBC. |
| 3 | Pressurization: Dry air or nitrogen is injected to a set pressure (e.g., 200kPa). |
| 4 | Stabilization: Maintain stable pressure for a set time (e.g., 3 seconds) for balance. |
| 5 | Leak Rate Measurement: System automatically measures leakage (e.g., <0.5 sccm is acceptable). |
| 6 | Result Output: Test result (OK/NG) is determined in real-time and uploaded to MES for traceability. |
4. Conclusion
Airtightness testing is one of the core processes for on-board chargers to meet waterproof standards, enhance electrical safety, and ensure high-reliability production quality.