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What Is a Battery Energy Storage System and What Are the Workplace Risks?

Apr 05, 2023
Battery energy storage system in a home garage

Traditional batteries are singing their swan song as they are rapidly replaced by lithium-ion batteries.

While they have long been in place in small forms for consumer electronics like cellphones and laptops, large-scale lithium-ion battery energy storage systems (BESSs) are now powering or backing up equipment like uninterrupted power sources, data centers, hospital imaging systems and more.

When compared to a traditional lead acid or nickel-based batteries, lithium-ion batteries have higher energy density, lower maintenance, higher performance and better longevity.

They are also quite safe; only 1 in 10 million lithium-ion batteries fails, according to the nonprofit Fire Protection Research Foundation.

“But when they go bad, they go really bad,” says James Trudeau, a 30-year veteran of the energy field and a former market development manager for energy and industrial automation with UL.

When a lithium-ion battery fails, it almost always catches on fire and can lead to explosion, which can cause massive damage, injury and death.

While the risk is alarming, Trudeau offers plain advice: “Don’t worry about it, just plan for it.”

During a webinar with ASSP, he provided an overview of  lithium-ion-dependent battery energy storage systems, the risks and exposures, ways to address these hazards, and the rules and regulations safety professionals should follow to protect businesses and their employees.

What Is a Battery Energy Storage System?

A battery energy storage system is a type of energy storage system that uses batteries to store and distribute energy as electricity. BESSs are often used to enable energy from renewable sources, like solar and wind, to be stored and released.

Lithium-ion batteries are currently the dominant storage technology for these large-scale systems.

“You’re all going to be dealing with this in some way or another,” Trudeau says, pointing to the switch to lithium-ion-powered electric vehicles, corporate focus on environmental, social and governance (ESG) standards driving electrification, and the continued trend to replace traditional lead acid batteries with lithium-ion versions.

Even if you don’t see them taking over yet, Trudeau says, your insurance company certainly does. Taking proactive steps to reduce the risks from these systems can mitigate rate increases and give your organization a better risk profile than your competitors, he adds.

What Are the Risks and Exposures of a Battery Energy Storage System?

Lithium-ion batteries can fail through overheating and cell rupture caused by factors like overcharging, short circuits and manufacturing defects. Their failure typically follows the same process—to see it you can look at this video.


When the battery fails, the “first thing you see is a white cloud of gas” from the electrolyte liquid inside the cell evaporating. This cloud, composed predominantly of hydrogen that Trudeau explains is 40% more explosive than propane, will fill the room where the battery is stored.

Then comes the fire, which can burn between 900 and 1500 degrees Celsius — hot enough to cause damage to structural steel. This fire can also create a thermal runaway, lighting other cells nearby on fire, causing them to subsequently fail as well.

“That’s not even the biggest problem,” Trudeau says. “The biggest problem is that they make their own oxygen — you cannot extinguish a lithium-ion battery fire. You can suppress it, you can keep it from spreading, but you can’t put it out. I can take a burning lithium-ion battery and drop it in seawater, it will continue to burn.”

The key is to have appropriate gas and heat detection measures and good ventilation.

“You’re not going to avoid the fire, but the fire is not as big of an issue as the explosion,” because the explosion poses the greatest risk to human life.

How Can Safety Professionals Mitigate the Risks?

While it’s important to understand how dangerous a battery energy storage system can be when it goes bad, the hazards and exposures can vary depending on how the system is set up.

Trudeau uses the example of a hospital replacing part of its uninterruptible power source with a standard 20-foot container of lithium-ion batteries. The operations manager has a choice: Place the BESS in the basement or place it outside, right by the generator.

The risk of failure is the same in both situations, but the risk to people and property is “a whole lot less outside than it is in the basement,” he says.

Safety professionals can employ three key measures when deploying a BESS to reduce risks and hazards and protect employees and property.

  • Distance: What is the distance between that system and everything else? The more distance you can create around a cell, the better.
  • Surroundings: Determine placement where the system can cause the least amount of potential damage.
  • Water: If a fire starts, do you have enough water to mitigate it?

Which Standards and Regulations Address Battery Energy Storage Systems?

The two primary standards relating to BESSs are: 33:45 IFC 2021 and NFPA 855.

“I think they’re excellent and they are evolving as we get smarter,” Trudeau says. While compliance isn’t necessary right now, both California and New York, which make up 65% of the energy market, require compliance with these codes, so most manufacturers follow them, he notes.

“As a user you need to be aware of what’s in these codes, so that when something gets installed in your facility, you know it’s compliant because compliance with these codes is what’s going to keep you safe,” he says.

The standards contain four key components:

  • Spaced minimum of three feet from other arrays and walls
  • Follow UL 9540
  • Maximum of 50 kWh per unit
  • Maximum of 5,600 kWh in aggregate or fire area

While it is possible a setup may not comply with all these rules because of mitigating factors, the design should then be lab-tested so a fire safety official can make a determination about its efficacy.

Key Steps to Take Today

“These batteries are coming into your facilities and you may not know they are there,” Trudeau says.

Because the use of lithium-ion batteries is widespread in small devices, they are likely already in use at your facility. But larger and more impactful energy storage systems are coming, so it’s vital to ensure they are placed and operated in a safe way.

Here’s what you can do today as a safety professional to address BESS risks:

  1. Get educated. Understanding the hazards and risks is a key first step. It’s also important to educate company leaders and employees. By proactively addressing the risks from lithium-ion batteries, you create a safer environment and potentially save your organization money.
  2. Know where they are. Talk to operations managers and anyone else who may be purchasing and deploying lithium-ion batteries. They need to know that you need to know.
  3. Apply the safety guidelines of distance, surrounding and water. Wherever you have battery energy storage systems or intend to install them, focus on those three key components.

Finally, Trudeau says that BESSs will uniquely impact different industries and locations. He encourages all safety professionals to contribute to developing standards through ASSP, UL or standards committees.

“Bless the rest of us with your input,” he says.

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