Data center fires raise concerns about lithium-ion batteries

Fire is to blame for a small but significant number of data-center outages including a March 28 fire that caused severe damage to a data center in France, and an analysis of global incidents highlights ongoing concerns about the safety of lithium-ion batteries and their risk of combustion.

The use of lithium ion (Li-ion) batteries in data centers is growing. Now commonly used in uninterruptible power supplies, they are expected to account for 38.5% of the data-center battery market by 2025, up from 15% in 2020, according to consulting firm Frost & Sullivan.

Adoption is driven by Li-ion batteries’ smaller footprint, simpler maintenance, and longer lifespan compared to lead-acid batteries. In addition, Li-ion energy storage is a key component in renewable energy distribution, according to Uptime Institute, which offers resiliency services, advice on building and running data centers, and certification services.

However, Li-ion batteries present a greater fire risk than valve-regulated lead-acid batteries, Uptime warns.

The firm found in its annual analysis of data-center reliability that 7% of outages were caused by fires. (Connectivity problems—which include issues with fiber, network software, and configuration—are the biggest cause, responsible for 29% of publicly reported outages.)

“We find, every time we do these surveys, fire doesn’t go away,” said Andy Lawrence, executive director of research at Uptime, in a conference call to discuss the firm’s new outage research.

Fire protection has always been a challenge when it comes to batteries and thermal runaway, when heat builds up in a battery faster than it can be dissipated. Over time, the industry has gotten a better understanding of what causes thermal runaway in lead-acid batteries and developed intelligent charging circuits that improve detection and avert problems, said Chris Brown, chief technical officer at Uptime.

“We learned a lot through the years with lead-acid batteries. Now, lithium ion comes onto the scene, and it’s a whole different animal,” Brown said.

Weigh the pros and cons of deploying Li-ion batteries.

Li-ion batteries burn hotter than lead-acid batteries, and if the battery-containment unit is damaged, it doesn’t react well with oxygen or water, Brown said. “We’re finding that we do not completely, truly understand all the failure modes of lithium-ion batteries at the moment, and the charging circuits are not able to cope with them all,” he said.

As with any battery, once a Li-ion battery starts to burn, it’s hard to put out. “It’s going to burn until it expends all of its energy, and just dumping water on it doesn’t really help. It keeps it from spreading, perhaps, but it doesn’t help,” Brown said. “And the fact that it burns much hotter than lead-acid batteries [means] it’s going to do a lot more damage. It’s going to burn a lot longer because it stores a lot more energy. And so that’s the problem we’re seeing with lithium-ion everywhere.”

In response, local authorities and regulatory agencies are enacting requirements related to the storage of Li-ion batteries.

Brown recommends data-center operators pay close attention to facility design if Li-ion batteries are part of the plan.

“If you are looking at using lithium-ion batteries, then definitely look at segregating them into their own battery room,” he said. A battery room should have at least a couple of fire-rated walls and ceilings, and operators should consider using a foam fire-suppression system “because at least foam will smother the fire and help to extinguish it, whereas water is just going to keep it from spreading.”

When asked about the use of distributed batteries, as opposed to a centralized UPS system with banks of batteries, Brown advises caution.

In the past, a conventional approach was to remove every type of combustible unit from the data hall itself. Now, with distributed batteries being installed in racks and rack-mounted UPSes, data-center operators have to weigh the energy-efficiency gains of distributed Li-ion batteries against the fire risks, Brown says.

“The good thing is that if it does catch fire, these are much smaller batteries, so you might be able to contain it to a few racks. However, there’s going to be smoke, and in the end, any racks in that vicinity are going to suck some of that debris into them. And while it may not cause failures today, that’s going to lead to premature failures in the future.”

People need to go into it with eyes wide open, perform a cost—benefit analysis, and do what’s best for them, Brown says. “But my recommendation is that you get batteries out of the data hall. That’s the most reliable, most resilient thing you can do.”

Recent data-center fires blamed on Li-ion batteries

Lawrence referred to instances in which Li-ion batteries are suspected to be the cause of data-center fires.

One of the most notorious incidents occurred in early 2021, when the largest cloud provider based in Europe, OVHcloud, suffered a catastrophic fire that destroyed one of its data centers in Strasbourg and damaged a neighboring one.

A Maxnod data center in France suffered a devasting fire on March 28, 2023, and “we believe it’s caused by lithium-ion battery fire,” Lawrence said.

A lithium-ion batter fire is also the reported cause of a major fire on Oct. 15, 2022, at a South Korea colocation facility owned by SK Group and operated by its C&C subsidiary. The fire at the SK C&C data center reportedly started in a battery room and affected the operations of  major South Korea tech companies.

“Most of South Korea suffered an eight-hour service disruption. CEOs resigned. Government investigations and multiple class-action lawsuits were initiated,” Uptime said.

The SK C&C incident took tens of thousands of servers offline, including the IT infrastructure running South Korea’s most popular messaging and single sign-on platform, KakaoTalk, wrote Daniel Bizo, research director at Uptime, in a blog post.

“The outage disrupted its integrated mobile payment system, transport app, gaming platform and music service—all of which are used by millions,” Bizo wrote. “The outage also affected domestic cloud giant Naver (the ‘Google of South Korea’) which reported disruption to its online search, shopping, media and blogging services.”

Kakao attributed the cause of the fire to the Li-ion batteries deployed at the facility; SK Group has not disclosed its official findings.