A Major Milestone for Battery Storage Safety
EticaAG announced today the completion of the battery energy storage industry’s first UL 9540A thermal runaway propagation testing for an immersion-cooled battery system, marking a major milestone in generating the safety data required to support the deployment of immersion-cooled battery energy storage systems.
UL 9540A is the recognized fire safety test method used to evaluate thermal runaway propagation in battery energy storage systems (BESS). The test intentionally drives a battery cell into failure and measures heat release, gas generation, and whether the failure spreads to neighboring cells or modules. The resulting data is used by regulators, engineers, and fire authorities to assess fire risk and establish installation requirements for energy storage projects.
EticaAG’s testing generated propagation data for its battery modules under UL 9540A conditions, providing information required for permitting, system evaluation, and safety documentation used by authorities having jurisdiction.
Demonstrating the Impact of Immersion Cooling
During pre-test trials with EticaAG’s immersion cooling active, thermal runaway could not be induced in the battery cells. The circulating dielectric immersion fluid maintained stable cell temperatures and prevented the initiating cell from transferring enough heat to neighboring cells to trigger propagation.
Because UL 9540A is specifically designed to evaluate propagation behavior, the test requires a cascading failure event so that heat release, gas generation, and fire dynamics can be measured.
To generate the required propagation data, the formal UL 9540A procedure was conducted with the immersion fluid removed from the module. This created an artificial worst-case condition that allowed a thermal event to develop so propagation metrics could be recorded.
While necessary for the testing protocol, this configuration does not represent how EticaAG systems operate in real-world deployments.
“The immersion liquid had to be removed at the module level to meet UL 9540A’s requirement to create cell-to-cell propagation, so the tested configuration was not representative of the final product,” said the NRTL certifier team lead.
“In our normal operating configuration, the cells are fully immersed in circulating dielectric fluid,” said Jaime Hidalgo, CEO of EticaAG. “That immersion environment maintains consistent cell temperatures and prevents heat transfer between cells that would otherwise allow thermal runaway to escalate.”
Understanding UL 9540A Testing
UL 9540A is widely used across the energy storage industry to characterize how battery systems behave during extreme failure scenarios and to inform spacing, ventilation, and fire protection requirements for installations.
The methodology progresses from cell-level evaluation to module-, unit-, and installation-level testing, measuring heat release, gas generation, and whether thermal runaway propagates from an initiating cell to adjacent cells or modules.
While UL 9540A provides valuable safety data, the test method is fundamentally designed to measure thermal runaway propagation once it occurs. As a result, the procedure requires a cascading failure event so that propagation behavior can be quantified.
This creates a challenge for technologies specifically engineered to prevent propagation entirely, since the test protocol does not yet include a standardized pathway for validating systems where propagation cannot be initiated under normal operating conditions.
For advanced battery architectures such as immersion-cooled systems, this limitation means certain test configurations may require modifications to enable propagation for measurement purposes.
Supporting Permitting and Safer Energy Storage Deployment
Completing UL 9540A testing is a critical step in meeting the safety documentation requirements used by regulators, fire authorities, and project developers when evaluating battery energy storage installations. The data supports permitting processes, informs system spacing and ventilation requirements, and helps demonstrate compliance with safety codes governing BESS deployment.
While the formal UL 9540A test configuration required removal of the immersion fluid to generate measurable propagation data, EticaAG’s production systems operate with battery cells fully immersed in circulating dielectric fluid. In field operation, this immersion environment maintains consistent cell temperatures and prevents the heat transfer pathways required for cell-to-cell propagation.
As energy storage deployment accelerates globally, regulators and developers are increasingly focused on technologies that prevent ignition, slow heat transfer, and contain hazardous gases during extreme failure events.
EticaAG addresses these safety concerns through:
- Direct cell-level thermal management
- Uniform temperature control across modules
- Prevention of cell-to-cell thermal propagation
- Integrated toxic gas containment systems
The company will use the official UL 9540A data, together with its immersion test data, to support project permitting, advance certification pathways, and guide continued product development as it prepares for commercial deployments.
