Proposed Standards And Methods For Leak Testing Lithium-Ion Battery Packs Using Glycol-based Coolant With Empirically Derived Rejection Limits
2022-01-0848
03/29/2022
- Event
- Content
- Lithium-ion batteries are a highly suitable energy source for many applications, particularly in the automotive sector due to their high energy density and low self-discharge rate. During the production of battery cells, rapid detection of leaks is essential to achieve necessary lifetime service-life and safety requirements. Once assembled into packs, whether made of prismatic, cylindrical or pouch cells, packs must be cooled by common automotive thermal management systems, for example those employing engine coolant and radiator, and in which manufacturers must prevent various leak-producing defects that affect durability, longevity and safety Two types of cooling systems are used in automobiles, an active variant in which refrigerant, compressor, evaporator and heat exchanger are used to operate the air conditioning system, or a passive variant with a cooling medium, typically a water/glycol mixture, and a heat exchanger cooled by ambient air. While good industry standards are established for refrigerant cooling, industry standards for the relation between measured test-gas leakage rates and the amount of glycol-based cooling liquid lost during operation in corresponding leakage channels do not exist. This presentation will discuss how leaks in water-glycol cooling circuits can be detected reliably and quantitatively through detection of escaping test gas as an indicator of ethylene glycol leaks and how the test gas leak rates correlate to the liquid leakage of the cooling liquid. Influencing variables such as leakage channel diameter, pressure difference and viscosity are considered, and go/no-go leak rates are described. This paper builds upon a 2021 SAE paper which discussed leak rates of pure water and clarified how many drops of that liquid emerge from a leak channel of various diameters and demonstrated comparing helium test gas leak rates. Comparisons of pure water to mixtures of water/glycol will be established.
- Citation
- Wetzig, D., and Blaufuß, M., "Proposed Standards And Methods For Leak Testing Lithium-Ion Battery Packs Using Glycol-based Coolant With Empirically Derived Rejection Limits," SAE Technical Paper 2022-01-0848, 2022, .