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Greater demands on EV batteries call for more stringent leak testing methods

Over the past few years, we have seen a substantial shift in the automotive market towards electric vehicles. As EV sales continue to rise, automobile manufacturers are extending their electric options to more of their line, which has included high-performance electric sports cars, trucks, and commercial vehicles—and now, off-road EVs. 

With this development of more off-road EVs, there come new challenges for manufacturers. These vehicles are subject to more extreme environmental conditions and hazards, calling for stringent testing and performance requirements on the battery packs that power these vehicles. 

Leak testing is integral to supporting the evolving performance needs of EV batteries

In order to ensure proper performance and safety in the field, EV batteries’ internal components must be protected from physical damage that may lead to any leakage of the liquid electrolyte from a battery cell. The electrolyte is a solution of lithium hexafluorophosphate salts. When this substance comes into contact with water, or even moisture present in ambient air, it can prompt a chemical reaction that can lead to fire or even an explosion. If the anode and cathode within a cell, already in very close proximity to one another, come in direct contact, it can cause a short that may lead to fire.

With manufacturing pressures pushing higher performance (further reducing the weight of a battery case), the internal and external structural elements of the battery pack are becoming thinner. With the increased performance requirements and this push towards lighter and thinner materials, leak testing has to evolve to keep pace.

Leak testing electric vehicles batteries to IP67 standards

When we quote a leak test system for an EV OEM or supplier, we ask for the target leak rate, test pressure, and desired test cycle time. However, we also look beyond the test station specs to consider the use case scenario in the field. 

We have to consider that off-road vehicles may be subjected to very extreme use case conditions where the likelihood of fluid or moisture ingress becomes an even greater concern. Another consideration is that everyday passenger vehicles may operate in areas of the country where frequent and severe annual flooding occurs due to changes in seasonal weather patterns. 

With these realities in mind, the IP67 rating has become the standard for many electric vehicle manufacturers. Any device or assembly rated to this standard must resist exposure to dust and withstand up to 30 minutes of submersion in water up to 40 inches (or one meter) in depth.

For internal battery pack components such as the coolant system, a pressure decay or mass flow leak test with pressurized air is sufficient. To meet the IP67 standard (or an even more stringent standard, if we are also concerned about water vapor penetration with fluctuations in ambient humidity and atmospheric pressure due to elevation changes), we have to switch to test methods that can reliably and quickly test to even lower target leak rates. For EV battery packs and cases, this means either a volumetric fill test with a vacuum or a tracer gas method.

Contact us to learn more about how we can help you find the best approach for your EV battery pack testing needs.
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