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.\nThe 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.\nAdoption is driven by Li-ion batteries\u2019 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.\nHowever, Li-ion batteries present a greater fire risk than valve-regulated lead-acid batteries, Uptime warns.\nThe firm found in its annual analysis of data-center reliability that 7% of outages were caused by fires. (Connectivity problems\u2014which include issues with fiber, network software, and configuration\u2014are one of the biggest causes, responsible for 29% of publicly reported outages.)\n\u201cWe find, every time we do these surveys, fire doesn\u2019t go away,\u201d said Andy Lawrence, executive director of research at Uptime, in a conference call to discuss the firm\u2019s new outage research.\nFire 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.\n\u201cWe learned a lot through the years with lead-acid batteries. Now, lithium ion comes onto the scene, and it\u2019s a whole different animal,\u201d Brown said.\nWeigh the pros and cons of deploying Li-ion batteries.\nLi-ion batteries burn hotter than lead-acid batteries, and if the battery-containment unit is damaged, it doesn\u2019t react well with oxygen or water, Brown said. \u201cWe\u2019re 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,\u201d he said.\nAs with any battery, once a Li-ion battery starts to burn, it's hard to put out.\u00a0\u201cIt\u2019s going to burn until it expends all of its energy, and just dumping water on it doesn\u2019t really help. It keeps it from spreading, perhaps, but it doesn\u2019t help,\u201d Brown said. \u201cAnd the fact that it burns much hotter than lead-acid batteries [means] it\u2019s going to do a lot more damage. It\u2019s going to burn a lot longer because it stores a lot more energy. And so that\u2019s the problem we\u2019re seeing with lithium-ion everywhere.\u201d\nIn response, local authorities and regulatory agencies are enacting requirements related to the storage of Li-ion batteries.\nBrown recommends data-center operators pay close attention to facility design if Li-ion batteries are part of the plan.\n\u201cIf you are looking at using lithium-ion batteries, then definitely look at segregating them into their own battery room,\u201d 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 \u201cbecause at least foam will smother the fire and help to extinguish it, whereas water is just going to keep it from spreading.\u201d\nWhen asked about the use of distributed batteries, as opposed to a centralized UPS system with banks of batteries, Brown advises caution.\nIn 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.\n\u201cThe 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\u2019s 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\u2019s going to lead to premature failures in the future.\u201d\nPeople need to go into it with eyes wide open, perform a cost\u2014benefit analysis, and do what\u2019s best for them, Brown says. \u201cBut my recommendation is that you get batteries out of the data hall. That\u2019s the most reliable, most resilient thing you can do.\u201d\nRecent data-center fires blamed on Li-ion batteries\nLawrence referred to instances in which Li-ion batteries are suspected to be the cause of data-center fires.\nOne 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.\nA Maxnod data center in France suffered a devasting fire on March 28, 2023, and \u201cwe believe it\u2019s caused by lithium-ion battery fire,\u201d Lawrence said.\nA lithium-ion battery 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\u00a0 major South Korea tech companies.\n\u201cMost of South Korea suffered an eight-hour service disruption. CEOs resigned. Government investigations and multiple class-action lawsuits were initiated,\u201d Uptime said.\nThe SK C&C incident took tens of thousands of servers offline, including the IT infrastructure running South Korea\u2019s most popular messaging and single sign-on platform, KakaoTalk, wrote Daniel Bizo, research director at Uptime, in a blog post.\n\u201cThe outage disrupted its integrated mobile payment system, transport app, gaming platform and music service\u2014all of which are used by millions,\u201d Bizo wrote. \u201cThe outage also affected domestic cloud giant Naver (the \u2018Google of South Korea\u2019) which reported disruption to its online search, shopping, media and blogging services.\u201d\nKakao attributed the cause of the fire to the Li-ion batteries deployed at the facility; SK Group has not disclosed its official findings.