Fire safety code conundrums continue for battery suppliers

battery question mark

Manufacturers of batteries for stationary energy storage are facing a moving target for fire safety code as written by the leading U.S. defining body for fire safety, the National Fire Protection Association (NFPA).

NFPA Code 855 is now in its third iteration, with a fourth and fifth already in the works. National electric codes follow NFPA code language, also adopted by city, county, and state jurisdictions, some sooner than others, creating a challenge for installers.

Several battery manufacturers and others have complained about the initial one-size-fits-all approach of 855, now four years old, which lumped requirements for all battery chemistries together. “The [2023] standard as written does not encompass various battery technology since the standard is lithium-ion technology centric, causing difficulties for other technologies required to comply with the large-scale fire and explosion testing requirements,” opined Robert Davidson, the principal at Davidson Code Concepts, in public comments to NFPA last year.

For example, lead-acid battery makers have been required to perform the same runaway fire tests as lithium-ion battery makers, adding to the cost of a system, according to one regulatory officer for a lead-acid battery maker. “We are going to spend around $1 million for testing costs for our lead-acid product line,” he said, asking not to be further identified.

“I don’t have a lot of good things to say about 855, which is nonetheless getting better. But it could be much better and move faster,” said the lead-acid battery source. “For example, most lead-acid systems now require a BMS [Building Management System], which adds several thousands of dollars to the cost of a system. A BMS is unnecessary and a waste of capital.”

BMS is a computer-based control system installed in buildings to control and monitor any building’s mechanical and electrical equipment such as ventilation, lighting, power systems, fire systems and security systems, comprising both software and hardware.

Similarly, energy storage systems (ESS) are subject to the same disconnect requirements regardless of the voltage in the system, points out Andrew Tanner, CTO at Yotta, which specializes in batteries that sit under rooftop solar panels. “However, the code doesn’t distinguish between high and low voltage for ESS yet, which seems inconsistent, because our battery can disconnect energized without hazard, given that our system is an array of low voltage microbatteries.”

The newer versions of NFPA 855 do distinguish between many battery chemistries and technologies, and groups those with similar hazard risks together. Each of these risk groups have been assigned a maximum permitted block size (see chart below), with a required spacing of one meter between blocks to mitigate runaway fire risk.

NFPA 855 chart

However, technology is moving faster than the codes, several sources point out, and there is a massive difference between iron phosphate and nickel manganese cobalt lithium-ion chemistries. “The ESS industry is still at this very early stage where code has not caught up to innovation,” says Tanner.

Code writers agree. Emerging technologies are always the hard part with the application of any code,” says Michael O`Brian, the principal at Code Savvy Consultants, who participates on NFPA 855 committees. “With the rapid change of alternative ESS designs, new technology manufacturers are going to have to show through testing that their systems are or are not like lithium-ion or other groups of products, and the hazards that they may present are properly mitigated.”

The need for ESS manufacturers to be pro-active in code development is paramount, others point out. “There is not an unwillingness on the part of the [855] committees to consider new technologies, but those producers need to step up and say ‘we need to be included’ and give the committee the information they need,” says Davidson.

The time and cost of participating in code development can be a burden on new or small manufacturers, some point out. “Unfortunately, the people with the greatest amount of time available to contribute to code development are not typically the disruptive technology companies, and since the code cycle is years long, you can risk missing the boat,” says Tanner.

UL 9540 echoes NFPA 855

NFPA 855 requires most new ESS installations to be listed in accordance with UL 9540, which includes focus on the safety of the battery system; functional safety; fire detection and suppression; containment; and environmental performance. Separately, UL 9540A is a specific test for system configurations over 20 kWh, intended to gauge thermal runaway risk.

This is especially focused on big cities and urban centers. Fire departments in New York City and San Francisco reported handling more than 660 fires involving lithium-ion batteries since 2019.

The third edition of UL 9540 came out in April 2023, reflecting changes including new provisions for lead-acid and nickel cadmium systems used in transportation, new noise requirements for ESS, and updates for information technology equipment. Overall, some 20 proposed changes to the code were adopted in the third edition, according to LaTanya Schwalb, principal engineer at UL Solutions, writing for the Sustainable Energy Action Committee (SEAC), a non-profit industry forum for regulation development.

The third edition of UL 9540 is published but not required until September 30, 2024, according to SEAC. Some jurisdictions are quick to adopt these codes, while others wait a year or more for revisions to be made. As a result, an ESS system might look very different in two different cities.

“New York City adopted UL 9540 early, then had to retract, once they found that there was already more lead-acid ESS installed there than in some countries, thanks mostly to telecommunications needs,” our lead-acid source said. “Similarly, some California and Nova Scotia jurisdictions have adopted it, so installers there are running into code problems, although the codes are still in flux.”

International adoption of U.S. Fire Codes Uneven?

One problem with the requirement for UL 9540 certification is that some foreign manufacturers are falsifying testing and just putting UL labels that U.S. manufacturers are being required to test toward.

“There are a ton of Chinese battery manufacturers saying their products are UL 9540 certified, but they are not doing the testing and just slapping on a UL label,” the lead-acid source said. “Several OEMs have asked us to put our names on their products, saying they’ll have UL labels. This is a trade issue that Commerce should look at.”

On January 1, 2012, Underwriters Laboratories became the parent company of a for-profit company in the United States named UL LLC, a limited liability corporation, which took over the product testing and certification business, according to Wikipedia.

Luckily, differences between international fire safety codes are being addressed this year, Davidson points out.

“The International Code Council board of directors created a new ad hoc ESS committee, charged with doing a gap analysis of all international codes to make sure they are providing reasonable requirements. If they see problems between codes, or the zoning of codes, they will encourage a solution and make sure it is not a roadblock to a given technology,” he said. “You have to look at these codes with a holistic approach to make sure they provide appropriate safety, but at same time eliminate roadblocks to a smooth transition,” he said.


Charles W. Thurston is a freelance contributor to Solar Builder.

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