What is Thermal Runaway? Common causes and how to prevent it

The more you know about thermal runaway, the better equipped you’ll be to prevent it from ever happening on your site, to your operations.

Lithium-ion battery fires are catching everyone out. E-bike sheds, construction sites, docks and even commercial flights are just some of the locations to experience lithium-ion (Li-ion) fires in recent times.

These aren’t any ordinary fires. They burn hot, they spread fast, and they’re incredibly difficult to put out. In some cases, the temperatures involved are such that the fires have actually re-ignited after having been extinguished. (More on that below.)

On the surface, they can be said to happen because of a phenomenon called thermal runaway, but it’s a lack of awareness of what this actually means that’s the real killer.

We hope this article answers any questions you have about thermal runaway and Li-ion fires so you can use your batteries to power your operations safely and responsibly.

What is thermal runaway?
Most fires burn themselves out. Now imagine one that doesn’t. Instead, it just keeps getting hotter and hotter, the energy it releases driving up the temperature, which in turn releases more energy…

This is the principle underlying thermal runaway: temperature increases release more energy, which further increases the temperature, and so on until whatever it is you’re looking at is very hot and incredibly dangerous.

“Lithium-ion battery fires are often self-sufficient and continue to burn without access to additional oxygen. This renders firefighting systems that rely on oxygen deprivation less effective. They may also continue to generate high amounts of heat following fire-extinction and are at risk of re-ignition.” BOAT International, ‘Spate of fires results in new yacht toy and tender guidelines’

Thermal runaway can be seen in all walks of science, from chemistry and electrical engineering to theories underpinning the way the environment is heating up. We’re most interested in it when it occurs in Li-ion batteries, where understanding the causes of thermal runaway and how to avoid it will help us all keep our operations and our people safe.

Thermal runaway causes
Thermal runaway is a dangerous phenomenon where a system, such as a lithium-ion battery, experiences a self-sustaining increase in temperature due to a chain reaction of events. The heat generated by chemical reactions inside the battery causes even more heat, leading to a continuous rise in temperature. This can result in the battery venting and releasing toxic flammable gases, exploding or catching fire. 

Causes of thermal runaway include:

●    Overcharging a battery beyond its safe max voltage

●    Multiple overdischarges followed by a charge

●    Rapid charging that can lead to excessive currents

●    Internal or external short circuit

●    High- and low-temperature environments

●    High moisture content

●    Physical damage to the battery via crushing or puncture. 

●    Manufacturing defects

Looking at the bigger picture, Li-ion fires are on the rise because the technology itself is becoming commonplace. As BOAT International reported, “a number of agencies have pointed to faulty or inadequately stored lithium-ion batteries as a suspected cause” of a spate of yacht fires last summer. IFSEC Insider echoes this in its recent article on fire safety in construction. 

As more industries like theirs make better use of electric vehicles, remote technology, and other handheld devices to power their operations, Li-ion batteries are popping up everywhere, often without consideration for the safety risks involved.

“Despite calls for greater professional competency and better technology available, fire hazards are only increasing with the likes of new construction materials, hot works and the presence of lithium-ion batteries.” IFSEC Insider, ‘Hot spots: fire hazards multiply to threaten construction sites’

Understanding lithium-ion thermal runaway temperatures
The rise in lithium-ion fires is attributed to the increasing prevalence of Li-ion batteries in various industries without adequate consideration for safety risks. Li-ion batteries are considered relatively safe up to 140 degrees Fahrenheit (60 degrees Celsius), but temperatures exceeding this threshold can make the battery unstable, leading to thermal runaway. 

In the event of thermal runaway, Lithium-ion fires catches fire at temperatures around 500 degrees Celsius (932 degrees Fahrenheit– and reach up to 1110°). Most concerningly, llithium-ion battery fires are prone to reigniting, because the lithium salts in the battery are self-oxidizing, which means that they can't be "starved out" like a traditional fire. 

How to avoid thermal runaway
There are several steps you can take to reduce the likelihood of thermal runaway.

It’s important to use high-quality Li-ion batteries with built-in safety features, such as overcharge and over-discharge protection. A high-quality battery is reliable and will set you off on the right foot from day one.

Avoid exposing the battery to high temperatures, as this can cause it to deteriorate.

Don’t leave your batteries on charge unattended, as this greatly increases the chance of them overcharging (and overheating)

Proper storage and handling of Li-ion batteries can go a long way towards preventing thermal runaway and ensuring safe and efficient operations.
How to extinguish a thermal runaway fire?
Specialist equipment is required to effectively extinguish a thermal runaway fire. Traditional methods, such as water, are less effective at bringing down the fire’s temperature due to the fact that thermal runaway keeps releasing more energy and raising the temperature again.

If you have invested in specialist storage solutions appropriate for your battery types, they may contain dedicated suppression systems and hazardous gas extraction to clear the air. Between them, these systems will help to control the fire, while the integrity of the storage solution should act to contain it.

Are lithium-ion batteries safe?
While Li-ion batteries are generally considered safe to use, the recent rise in reported Li-ion fires highlights the need for better education and training around the risks involved.

These fires can cause catastrophic damage if left unchecked, so don’t let thermal runaway catch you out. Follow the recommended steps, such as investing in adequate storage equipment and sticking to best practices, and make sure your team is doing the same.

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