70 that allow operators to track real-time data for immediate detection and later statistical analysis. As an alternative to tracer gases, such as helium and hydrogen, some systems use a signature air, which is typically a proprietary mixture that creates a vapour designed to be detected by the manufacturer’s own equipment, such as handheld sniffer devices. This technology is designed to find gas and coolant leaks in batteries, and it can be tailored to the OEM’s needs in terms of parameters such as sensitivity, and it can be updated to handle new vehicle models and battery configurations with a software update. It can also be customised to solve particular issues. For platform standard scenarios, one equipment developer resolves to five decimal places when measuring in PSI, enabling a significant reduction in testing time while maintaining accuracy and repeatability. It emphasises that the equipment can find very small leaks that are undetectable using outdated methods such as soapy water. In many applications, it is important to provide live graphing and reporting at every diagnostic stage, and the battery and coolant leak detector does that, capturing data continuously, followed by extensive reports that can be saved and sent to stakeholders. Leak detectors used during manufacture are typically designed to find just one type of gas: the tracer gas or signature vapour they are expecting. Dual gas detectors that target helium and hydrogen are available, and they are tuned to detect one type of gas at a time. Those based on industrialgrade mass spectrometers offer high sensitivity, fast response and a compact footprint. Such selectivity is very important to avoid false alarms. Unfortunately, all gas sensors have issues with reactivity to a variety of chemicals, so systems have to be engineered and operated to minimise the risk of confusion. Clearing the background For example, EV thermal-management systems increasingly include refrigerant circuits, and if there is a nearby refrigerant filling station it may emit that gas through connectors and create a background of that gas, making detection more difficult. Therefore, advanced leak detectors incorporate intelligent signal algorithms developed to differentiate between emissions due to leakage and background gas emissions. In general, leak testing systems can cope very well with the range of sizes and pressures they are likely to encounter in batteries, from small components to large, complete packs. Precision pressure-based testers can cover ranges from full vacuum up to 20 bar, and volumes from 0.1 cm³ to 1 m³. One supplier emphasises its ability to test everything from a tiny cooling plate for a car to a “massive” bus battery enclosure within a single platform. With vent valves incorporating pass-through leak check devices, the limitations are set by the robustness of the battery case and other components. While colorimetric leak detectors are not limited in the size of the parts on which they can be used, as parts get bigger, the system will need a larger gas generator and/or higher pressure to cause the colour change within a specified time. Integration issues Integrating leak detection into battery manufacturing processes is essential for quality control as production rates and volumes increase, and such integration March/April 2025 | E-Mobility Engineering EWI’s LeakSight is a chemical reagent that, when applied to seams, joints etc, turns permanently from clear to purple when exposed to ozone challenge gas injected into the part under test (Image courtesy of EWI) Dual gas detectors that target helium and hydrogen are available, and they are tuned to detect one type of gas at a time
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