Cosmos Magazine: What are the fire safety risks of lithium-ion batteries?

There are at least a dozen big batteries operating and dozens more under construction or announced around Australia.

Because of their energy density, lithium-ion batteries are becoming much more common - which means that, while rare, battery fires are becoming more common too.

The technology goes small too: the device you're reading on right now is probably powered by a lithium-ion battery.

With all new technology comes new risks. What will we need to think about as these batteries become ubiquitous?

The central risk with lithium-ion batteries is fire. The batteries are unlikely to catch fire - but they can, through faults inside the battery, or from external damage.

And when they do catch fire, the consequences can be serious.

"Lithium-ion batteries are actually quite advanced systems: they do have a lot of built-in risk mitigation measures," says Dr Amer Magrabi, principal fire engineer at Lote Consulting.

Cosmos spoke to Dr Magrabi at the 2022 Australasian Fire and Emergency Services Council (AFAC) conference in Adelaide, where he'd given a talk on battery fire safety.

"It's an emerging risk, we're still coming to grips with it. It's very different from any other battery system we have," Dr Magrabi said.

Once alight, lithium-ion battery fires are very hard to extinguish. Common fire suppressants don't work and the fire can burn very fiercely. In some circumstances, the battery can explode.

"If you have a problem with one cell, it's going to start spreading," Dr Magrabi said.

This unstoppable fire is called "thermal runaway" which is carefully explained in this video from emergency responder training company evfiresafe.com.

Water may assist with absorbing heat from some small fires, but it reacts dramatically with lithium - making it a bad decision to go directly on fires.

Lithium-ion fires also don't burn cleanly: batteries can vent toxic gases into the surrounding area. It's not always clear what these gases will be - Dr Magrabi refers to big batteries as "black boxes."

"The battery chemistry is a closely guarded commercial secret," Dr Magrabi said.

For these reasons, some fire services have a code of not intervening in lithium-ion battery fires: they're unlikely to suppress them because the risk to firefighters is too high.

Instead, they wait for the reaction to finish, and protect the surrounding environment.

They are rare. Batteries come with systems designed to prevent fires from starting.

"It is a low probability event, but it is a high consequence," Dr Magrabi said.

Industrial-scale batteries in particular have very sophisticated safety systems, designed to detect and prevent thermal runaway from happening (more on that later).

There are several different best practice guidelines designed to ensure that, even if one battery unit catches fire, the spread of fire is mitigated. This was seen at last year's Tesla plant fire in Geelong.

Electric vehicle fires are similarly rare.

EV Firesafe research suggests that passenger electric vehicles have an 0.0012 per cent chance of catching fire: from 2010-2020, there were 104 confirmed EV fires and 24 under investigation, from 10 million passenger EVs on the road.

"I think I'm more worried about domestic batteries and stuff you buy off the internet because there's actually no standards," Dr Magrabi said.

"I can just go on the internet and buy an electric scooter, or similar. And then I could charge it at home. But my charging system at home is probably not as sophisticated as what's required to pick up if things go wrong."

Charging is often where the highest risk lies for spontaneous combustion. In Magrabi's opinion, these light electric vehicles and similarly-sized batteries need more attention from authorities.

"That needs a bit more regulation."

"Depending on what battery chemistry you've got, the general rule of thumb is that once you get abuse or short circuit or damage, then you've got 12 minutes before the battery reaches thermal runaway," Dr Magrabi said.

"If you're able to pick it up before those 12 minutes, and you can basically turn off the battery, then that's it."

Big batteries are equipped with detectors to spot any off-gas vented by a battery - the signal that it's about to go up.

"Every battery has got that detection onboard, but it comes in different levels of sophistication," Dr Magrabi said.

"Your phone charger has also got a battery management system, where it basically always turns it off. But the sophistication of that is not as good as say, a control system on a big battery bank," Dr Magrabi said.

Who's responsible for making battery fires less dangerous? Should battery makers work harder on their safety systems, or do emergency services need to get better at responding to them?

"It's got to be a combination of both," Dr Magrabi said.

"You're going to have a lot of measures to try and mitigate the risk of the incident. Then you're also going to have technology developing to suppress the fire."

While the current safest method is just to wait for the fire to burn out, researchers are working on better suppression techniques.

"There's actually a lithium fire extinguisher on the market at the moment. It's not listed for use in Australia, but it's available," Dr Magrabi said.

At the moment, we don't have regulations in place to ensure that such a fire extinguisher is safe.

Because the chances of something going wrong are so low, the benefits of big batteries are generally calculated to outweigh the costs.

"It's something we've got to live with," Dr Magrabi said.

Originally published by Cosmos as What are the fire safety risks of lithium-ion batteries?