How Often Do Batteries Catch Fire?
By Shawn Lee
How often do batteries catch fire? There is a lot to this seemingly simple question. Battery systems can cost 100s of millions of dollars. Between 2017 and 2019, South Korea had 23 battery fires across multiple battery providers. LG Chem, one of the world’s premier battery manufacturers, lost $124M on its energy storage business in the first quarter of 2019 after seven consecutive quarters of profits. An Energy Ministry inquiry suspended five of the country’s 1,490 energy storage facilities during its audit, blaming poor installation quality, incomplete electrical shock protection, and a lack of overall controls for integrated systems. [1]
Lithium-ion batteries, the most common type, store energy by moving lithium ions between an anode comprising a high energy state material (generally some sort of neutral graphite) and a cathode comprising a low energy holding material (some kind of oxide). These two materials are kept electrically separated, which forces the electrons to flow in an outside circuit, where these electrons ultimately power anything from a lightbulb to a full electric car.
If for, whatever reason, the battery forms an internal electrical connection between the anode and the cathode, the battery will discharge all its energy through this short circuit in an uncontrolled fashion. This internal short circuit can be created by degradation due to the Battery Management System repeatedly discharging the battery too quickly or operating it out of its temperature range, or due to some sort of manufacturing fault. Either way, once the battery creates an internal short, it discharges a bunch of energy very quickly, and generates enough heat to boil liquid hydrocarbon electrolyte that separates the two materials (which incidentally is normally carcinogenic).
In most properly designed battery cells, the cell will vent the hydrocarbon vapor through pressure relief points. If the cell isn’t properly designed, the battery cell could burst in an unexpected way. In both cases, there’s now a hot hydrocarbon vapor mixing with atmospheric oxygen, which is perfectly capable of conflagrating and overheating the nearest intact battery cell and causing it to burn as well.
Very quickly, the effect can be a runaway fire burning from unit to unit. Developers can mitigate this by installing the batteries outdoors, using active fire suppression systems, separating clusters of battery units in space, and actively monitoring key parts of the battery and proactively taking parts offline and replacing them before they cause a fire.
When a battery fire happens, it’s a very high-profile event. The fire is typically very hot, can burn for longer than other kinds of fires, and the event can erode public support for new battery systems because they’re perceived as less well understood. Of course, no power technology is immune from fire.
The good news, however, is that as an industry, we are no longer really in the wild west of battery fires. The frequency of large battery fires is easy to find, since they almost always make their way into the news. Fire data reported by the Electric Power Research Institute [2] combined with data on installed batteries in the United States from the Energy Information Administration, gives us a true sense of the yearly rate of failures. Large changes to the failure rate year on year are indicative of an immature industry still working out its kinks.
The battery industry reflected an immature industry before 2014. However, since then, US BESS failure rates have been relatively consistent, showing that even though we’ve yet to settle on a consensus on fire codes, internationally or within the United States, the battery industry overall has settled into a consistent fire rate. Of course, when they do happen, fires can be catastrophic and design practices play a part in limiting both the occurrence of fires, and their consequences.
At NER, we use an understanding of battery failure rates, and a technical understanding of individual root causes and mitigations, to support battery projects with warranty backstops and Battery Dispatch Insurance products which can supplement standard property covers and help batteries deploy at scale.
Sources:
[1] https://www.spglobal.com/marketintelligence/en/news-insights/trending/bVy2KGU3Opsle5Vv8QG0-Q2
[2] https://www.pv-magazine-australia.com/2021/09/28/australias-biggest-battery-cleared-for-testing-following-fire-fallout/