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Guide to Storage Safety Certifications

As more battery energy storage systems (BESS) are connected to the grid, safety is paramount. That’s why clear safety standards exist for the storage industry; protocols including UL 9540, UL 9540A, and NFPA 855 aim to quantify how well batteries stand up to worst-case situations. All of EVLO’s product safety tests are performed by independent North American third-party testers to ensure objective evaluation. Here’s our guide to the most important safety standards for BESS, and why they matter:

UL 9540: The Safety Standard

UL 9540 is a safety standard for the construction, manufacturing, performance testing, and marking of grid-tied BESS and those operating in standalone mode. As the foremost safety benchmark for grid storage systems, UL 9540 is a roadmap for ensuring battery systems’ overall safety and reliability.

This standard covers electrical, mechanical, thermal, and environmental dimensions over a battery’s entire operation and fault scenarios. This includes assessing stability during charging/discharging, vulnerability to thermal failures, explosion risks, fluid hazards, and more.

UL 9540 certification requires demonstrating robust functional safety governance, fire prevention and response preparedness, explosion containment provisions, hazard detection sensitivity, and resistance to cascading failures. This holistic analysis provides confidence in responsibly mitigating worst-case outcomes.

For EVLO, achieving UL 9540 verification underscores our commitment to engineering safety and resilience into the core of our storage solutions. UL 9540 is more rigorous than on-site certification and includes continuous inspections up to 4 times per year. It is also more transparent, with all certification documents being publicly available. Finally, and most importantly, UL 9540 certification increases efficiency and avoids costly project delays related to on-site product modifications.

UL 9540A: Evaluating Thermal Runaway Response

While UL 9540 sets overall safety standards, UL 9540A describes a test method to assess fire risks in particular – quantifying how well systems contain thermal threats. While not a certification, a system’s UL 9540A test results provide essential data on its fire safety.

This test consists of deliberately inducing thermal runaway under controlled conditions. Engineers then evaluate the results at up to four successive levels:

  • Cell testing for flammability, thermal runaway potential and gases characteristics
  • Module testing for cell-to-cell propagation
  • Unit testing for thermal runaway propagation and explosion risk
  • Installation testing for validation of integrated fire mitigation systems

  • The BESS’ fire mitigation strategy should slow down thermal runaway propagation and contain it in a single module, protecting the rest of the system. Unique in the battery industry, all of EVLO’s BESS contain effective fire mitigation protection mechanisms at every level above the cell level. Our EVLOFLEX model recently obtained the UL 9540 certification after having met the UL 9540A performance criterion for thermal runaway containment at cell, module, and unit level, underscoring the system’s industry-leading safety features. In addition, on a voluntary basis, EVLO will perform a system-level test as an engineering best practice to validate the system mitigation strategy.

NFPA 855

In 2019, the National Fire Protection Association (NFPA) published NFPA 855, “Standard for the Installation of Energy Storage Systems.” This overarching standard lays out requirements for large-scale fire testing and determining appropriate mitigation strategies for stationary storage systems. NFPA 855 approves two options to manage thermal runaway in BESS enclosures: NFPA 69, which describes active approaches, and NFPA 68, which covers passive approaches. EVLO uses NFPA 69 as the main design philosophy guideline, but goes one step further by making sure that gases can be evacuated even when auxiliary power sources are off to ensure maximum safety.

NFPA 68: Passive Explosion Mitigation

NFPA 68 describes a passive method for explosion mitigation in battery enclosures. This method relies on deflagration panels, which are sheets of metal designed to rupture when pressure builds. The panels open to release pressure in the event of an explosion.

NFPA 68 methodology contains some considerable drawbacks. First , it allows explosions to occur, destroying individual units in the process. As a result, units meant for actual use in a storage system can’t be tested or validated individually.

NFPA 69: Active Explosion Prevention

In contrast to NFPA 68, NFPA 69 focuses on stopping explosions before they start. NFPA 69-validated systems contain extensive sensor systems that detect risks early. When threats emerge, the system automatically and actively ventilates gases to inhibit ignition potential and prevent an explosion.

NFPA 69 systems allow unaffected battery units to remain intact. This saves customers replacement costs should a thermal runaway event occur and allows rigorous testing and validation of each individual unit, including annual maintenance.

The EVLO Difference: Going Beyond in Fire Safety

At EVLO, we hold ourselves to a higher standard when it comes to building reliable and safe battery storage.

EVLO’s NFPA 69++

Our approach goes beyond NFPA 69 requirements because we add passive fire mitigation elements on top of our active strategies. Namely, our failsafe venting panels open by themselves to release pressure even during a power outage. Furthermore, panel sizing and internal BESS architecture meets NFPA 69 performance criteria through natural convection only. We call this approach NFPA 69++.

Tests for Extreme Weather Conditions 

Some environments pose particular challenges for battery safety. At EVLO, we ensure that battery systems undergo and pass additional testing for any weather conditions they may encounter. For projects near the sea or in rainy areas, EVLO batteries are tested and certified for resistance to water exposure and flooding safety. Those meant for use in earthquake-prone areas, such as California, are subjected to seismic safety analysis to ensure that they will remain stable – even when the earth itself isn’t.

As temperatures rise worldwide, battery function and safety in extreme temperatures is paramount. EVLO batteries have been rated with a wide operating temperature range from -40℃ to 55℃, ensuring optimal performance and reliability even under the most challenging environmental conditions.

Additional Safety Measures

In order to understand phenomena and master safety aspects, EVLO has developed a cell characterization methodology. This methodology makes it possible to select the most efficient and reliable battery cells without compromising safety. This methodology includes battery safety and abusive testing at cell level and performance characterization testing under a variety of use cases and conditions. To do so, we collaborate with Hydro-Quebec’s Center of Excellence in Transportation Electrification and Energy Storage (CETEES). These tests exceed the requirements and standards in the field in order to investigate different solutions. This allows us to integrate performance and safety data into the design of our BESS solutions.

By preventing emergencies in addition to controlling damage, our commitment to safety exceeds industry norms. That’s why communities can confidently depend on EVLO solutions to power their clean energy future safely and sustainably.