One-sentence answer: The power battery cold plate is a thin-walled part formed by welding the cold plate flow channels and the manifold. A micro-leak at the weld seam will cause coolant to seep into the battery pack and lead to insulation failure. Using the CTS Sentinel A28 differential pressure leak detector, the air tightness of the cold plate flow channels is tested by comparing a master part with the part under test, which can offset misjudgment caused by workshop temperature fluctuations to the greatest extent and is suitable for 100% inspection and sampling inspection on mass production lines.
Long weld seams and thin walls mean micron-level pores cannot be seen before assembly; differential pressure leak testing catches them piece by piece
Cold plates are mostly made of aluminum using friction stir welding or brazing. The flow channels and manifold have long weld seams and thin walls. Micron-level pores are completely invisible before assembly and only leak during pressure cycling after the vehicle is assembled.
Cold plate testing is usually carried out in stamping and welding workshops. Day-night temperature differences and air-conditioning airflow cause the gas inside the workpiece to expand and contract with heat, making pressure readings drift. This can lead to missed detection in mild cases, or rejecting conforming parts in severe cases, and repeated retesting slows down the cycle time.
After the previous cleaning process, residual moisture remains in the flow channels. After inflation, it vaporizes or condenses, causing unstable pressure and poor test repeatability.
The cold plate has three main sealing locations:
Consequences of leakage: coolant seeps into the battery pack, reducing insulation resistance and corroding tabs and busbars, and in severe cases causing short circuits and thermal runaway. At the same time, the cooling circuit cannot maintain pressure, battery temperature control fails, and fast-charging power is forced to be derated.
The difficulty in cold plate testing is not "whether a leak can be detected," but stably distinguishing true leaks from temperature drift on large-area thin-walled parts. This is exactly the design orientation of the A28 differential pressure model:
If the cold plate also needs to handle large-volume battery housings and multiple test methods need to be connected in series within the same instrument, the multi-function single-station model I28 can be used instead. If only single-piece, single-method vacuum decay testing is required, the C28 (vacuum decay/direct pressure) is also a common configuration.
In scenarios with stable ambient temperature and high workpiece consistency, direct pressure can be used (such as the pressure decay/vacuum decay configuration of the CTS C28WE). When workshop temperature differences are large and thin walls are easily affected by temperature, the differential pressure method should be preferred. By comparing the master part with the part under test, the A28 can offset errors caused by ambient temperature fluctuations to the greatest extent and provides better stability.
The cycle time depends on flow channel volume, inflation pressure, and stabilization time, and must be calibrated based on actual measurements of the workpiece. A fixed number of seconds cannot be applied universally. In practice, use a small number of workpieces for gradient testing to find the shortest stabilization time that ensures stable pressure and no missed detection, then write it into the A28 test program.
Use the instrument's built-in calibrated leak to perform automatic calibration and self-test, and keep calibration records. Daily pre-shift checks plus regular verification with a calibrated leak are the prerequisites for ensuring that the 100% inspection conclusions for cold plates are credible.
The core of cold plate sealing testing is stably identifying true leaks under temperature disturbance. The differential pressure comparison structure of the CTS Sentinel A28 directly addresses this point. Combined with custom plugging fixtures and 32 test programs, it can cover the 100% inspection requirements of mass production lines for multiple cold plate models. For a vehicle model that needs continuous mass production for several years, choosing the right test principle is more important than piling up specifications.
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