Energy storage systems provide essential functionality for electrical infrastructure — and with massive increases in renewable energy generation and transportation electrification on the horizon, it's important these systems are engineered with safety in mind.

In particular, lithium-ion batteries are becoming increasingly common in today’s mission critical environments — whether they're embedded within UPSs, emergency power systems, or distributed energy installations. As energy storage technology evolves, so do the codes and standards for safe application and guidelines for system testing. To stay informed on the latest standards and testing guidelines behind the technology, Mission Critical spoke with Ed Spears, product marketing manager for critical power solutions at Eaton.

Mission Critical: What are the most important codes and standards supporting safe energy storage?

Spears: Several electrical industry organizations currently offer guidelines and best practices for the installation and testing of battery energy storage technology. The most recent code developments for energy storage systems include:

  • National Fire Protection Association/NFPA 855 — Standard for the Installation of Energy Storage Systems.
  • International Fire Code/IFC 1206 — Energy Storage Systems.
  • UL 9540A — A test method for fire safety hazards associated with propagating thermal runaway within battery systems.

Although similar safety guidelines for energy storage systems have been in place for many years, the mandatory adoption of National Fire Protection Association (NFPA) and UL testing guidelines depends on where the energy storage system is applied and the version of the National Electrical Code (NEC) and International Fire Code (IFC) that is applied in the jurisdiction. This lack of consistency has created confusion. How can you be sure that your battery energy storage system (BESS) is installed correctly and will operate safely for years to come?

There is an entire ecosystem of working components that is part of energy storage systems, and each one has a role to play in enhancing the safety of the overall system. These components have long been required by NFPA codes and include unique certification criteria for circuit protection devices, inverters, battery management systems, and more. I believe the testing methodology outlined by UL 9540A should be considered in line with the NFPA 855 guidelines to ensure the long-term safety of battery energy storage systems.


Mission Critical: Why is the UL 9540A testing process important? How does it work for energy storage installations?

Spears: Although codes and standards vary by region, I believe it is important for everyone to understand the testing process UL recommends for safe energy storage installation and operation. A thorough understanding of this process will help you provide your local authorities, insurance providers, and fire mitigation professionals with the information they need to quickly assess the safety of your installed battery energy storage system.

The UL 9540A test method was developed to evaluate the potential for thermal runaway fire propagation should it occur during the life of the system. Test result documentation allows the authority having jurisdiction (AHJ) to address key issues identified by building codes and the fire service, including:

  • Proper BESS installation.
  • Compliance with installation ventilation requirements.
  • Effectiveness of fire protection (integral or external).
  • Applied fire service strategy and tactics.

Here’s a high level look into the how the testing process works.

  1. Cell-level test — Identifies whether the battery cell itself can exhibit thermal runaway and if the connected battery management system (BMS) can take appropriate action to mitigate the problem.
  2. Module level test — Determines the propensity for propagation of thermal runaway and the effectiveness of BMS control systems.
  3. Unit level test — Evaluates fire spread should a thermal event occur.
  4. Installation level test — Rates the effectiveness of physical fire protection systems.


Mission Critical: Are there any other important considerations when it comes to designing safe energy storage systems?

Spears: In my opinion, it’s essential to recognize the safety of energy storage doesn’t start and end at the battery. There are layers of protection supporting safe energy storage systems. Batteries are only one piece of this puzzle. There are a host of other components that have applicable codes designed to enhance the safety of the overall system.

  • UL 489 circuit breakers provide overload (thermal) and short-circuit (magnetic) protection to a circuit and its downstream components, like batteries.
  • UL 489B molded-case circuit breakers, molded-case switches, and circuit breaker enclosures are certified for use with photovoltaic (PV) systems and DC applications.
  • UL 1741 storage inverters are certified to remain online and automatically adapt power output in real time to stabilize the electric grid during periods of abnormal operation, such as heat waves or brownouts.
  • UL 1998- and UL 1973-certified battery management systems provide confidence that the battery and related management systems support safety functions in the case of a failure.

Before designing or installing an energy storage system, it is critical to familiarize yourself with the code requirements beyond the physical battery system that help keep people and property safe. As with any electrical product, it is important to source this equipment from trusted suppliers who can provide evidence of third-party testing when possible.

Mission Critical: Are there any additional resources on the topic?

Spears: Energy storage is growing and has vast potential to transform how we produce and consume electrical energy. To support the growth of this transformative technology, it is essential that proper precautions be put into place to advance safety.

Understanding the codes and standards related to energy storage is a start, but many requirements vary by region. I recommend that you use the latest NFPA guidelines as a baseline when designing and installing battery energy storage systems and find confidence in the thorough testing and reporting processes outlined by UL 9540A. Most importantly, we recommend consulting early and directly with the local AHJ during the conceptual or design stage of the energy storage system environment. If waivers or exceptions to the codes are applicable, the AHJ may have the final say. Direct consultation will provide the confidence upfront that the planned installation will be accepted and approved.

Battery safety is a critical factor to the technology’s widespread adoption in the energy marketplace. A commitment to safety when it comes to the installation and operation of these systems will enable the energy transition with a more dynamic ecosystem, capable of providing much more sustainable electricity than ever before.