SAE J-3277 Covers Leak Testing for Every EV Battery

Up next in RESS safety is J3337, which applies to lithium-ion (Li-Ion) and sodium-ion (Na-Ion) cells regardless of construction.

April 16, 2025

Thom Cannell

When testing individual cells, cells are placed into a vacuum chamber, and a vacuum is established. Any leaking electrolyte can then be detected (the red cloud represents the escaping electrolyte). (Inficon)

North American EV battery manufacturers currently do not test 100% of the cells they assemble into Rechargeable Energy Storage Systems (RESS, or battery packs) for electrolyte leakage. This can lead to missed defects, high warranty costs and reputational damage. Until SAE J3277_202404 described an evaluation methodology to ensure battery pack integrity, there were also no standards for leak testing of assembled battery packs.

Robotic sniffer leak detection swiftly and accurately detects leaks in completed battery packs. The internal cooling circuit may be tested prior to or after pack lids are attached. (Marposs)

SAE Battery Standards Testing Committee sponsor Hemi Sagi of Advanced Test Concepts wrote recently that hurricanes Ian and Idalia “demonstrated that current EVs aren’t well protected against water ingress into the battery pack.” Various manufacturer’s vehicles, an estimated 3,000-5-000 EVs, experienced water ingress and approximately 600 EVs were a total loss. Of those, an estimated 36 EVs experienced thermal run-down (fire).

Eaton said its new 3-in-1 battery vent valve is the first on the market to align with the new SAE J3277 standard, which is designed to evaluate non-destructive water intrusion testing. (Eaton)

“Every battery cell, prior to assembly into a module and again after module fabrication, should be leak tested to prevent water vapor ingress,” said Thomas Parker, INFICON automotive sales manager and committee member, told SAE Media. “Cells and modules require testing at multiple stages, and once assembled into a completed battery pack, that pack should be tested to prevent liquid water ingress. Before attaching the lid to the battery pack, the internal glycol cooling circuits should be leak tested to a level that prevents that cooling liquid from leaking into the pack from the inside. Leak testing to the correct levels is critical to the battery performance and safety.”

J3277 lists methods for leak testing every RESS to ensure that liquid water ingress prevention meets standards. It also suggests both water ingress test(s) and coolant ingress tests. Testing typically uses a test gas, helium or forming gas, as leak tightness specifications like IP67 – 30 minutes under 1 m (3.2 ft) of water – would be unworkable.

Currently, assembled RESS/battery packs are pressurized with test gas, and a robotic sniffer probe checks for leaks. Cooling circuits may be tested by pressure decay methods or with a test gas. While this ensures that battery packs are leak-free at the time of testing, pack integrity alone may not provide optimum safety as each metal-ion cell preferred for EV propulsion must be leak-free to prevent liquid or atmospheric moisture from causing dangerous degradation. SAE is currently evolving a new standard for cell package integrity and testing, J3337, to address cell-level electrolyte leakage.

The Work in Progress J3337 applies to lithium-ion (Li-Ion) and sodium-ion (Na-Ion) cells regardless of construction and describes non-destructive testing, typically requiring a vacuum chamber(s) and spectrophotometer to search for any volatiles linked to the electrolyte. Using test gas also negates any material concern. For instance, there are significant differences in the leak rate, from 2.9E-6 mbar*l/s for aluminum to 4.8E-3 mbar*l/s for steel due to their different wetting properties (contact angles). Today, testing individual cells to the 10-6 mbar l/s range through the detection of escaping ethylene glycol is easily accomplished at full production-line speeds.

In March, Eaton announced a new 3-in-1 battery vent valve that would be the first to meet the new standard. The valve integrates passive and active venting, a battery case leak-check mechanism and a way to reseal the pack with a lower opening pressure. The new valve allows the battery to relieve pressure in an attempt to prevent catastrophic thermal runaway scenarios and allows engineers to conduct high-precision, non-destructive leak testing during production, Eaton said.