A burning question

What are the risks of lithium batteries (14 minute read)

In 2005, I took my lime-green Nokia 5110 to a mobile phone shop. I’d had it five years and it had performed great service, but the battery had reached a point where it would only hold a charge for a few hours. Would it be possible, I asked, to replace the battery?

The sales assistant, to his credit, didn’t laugh at me. He told me that unfortunately they no longer made batteries for my phone. But, he said, he knew which phone I should get. It was exactly the same as my old phone, but half the size. Although it was officially known as the Nokia 1100, I christened it the technophobe. It was the kind of mobile phone loved by people who didn’t care about fancy features and didn’t want to learn a completely new system every time they bought a new phone. I used mine for ten years, and I know people who kept theirs going longer.

One of the things I remember from those old phones was that the battery charge really lasted, often for nearly a week if I didn’t use it much. These days, I’m happy if my phone battery lasts a day. This isn’t the fault of the battery, though. My current phone, one of the smaller iphones from 2020, has more than twice the capacity of my little Nokia 1100. But we ask our phones to do so much more now.

The revolution in mobile phones is the result of many different technological advances. One in particular has been on my mind lately – the battery. It’s an amazing invention which has changed our lives in so many ways. We’ve brought dozens of them into our homes and seldom give them a second thought. But we should. Batteries hold a great deal of energy, and while they mostly direct that energy where we want it, occasionally they can go wrong.

I’d never given this much thought, until I had a chance conversation with someone from Fire and Emergency New Zealand. From that conversation, I realised that the batteries we use every day have certain risks. Everything has risks, of course. Last night, in the process of cooking dinner, I used a knife which I had sharpened on the knife steel I inherited from my grandfather, cooked over a gas flame, opened a can of tomatoes, leaving a sharp-edged lid, and added lentils, which are toxic when raw. We know that cooking has dangers and we teach children from an early age to be safe in the kitchen. We know how to manage these risks.

What I realised about batteries is that I didn’t understand what the risks were. Because I didn’t understand the risks, I also didn’t know how to manage them. I realised, too, that most people I knew were also unaware. So, I decided to write about batteries and battery safety. I followed up on my chance conversation and interviewed a couple of people from Fire and Emergency New Zealand, but before I get to my conversation with them, I’m going to step back and take a look at what batteries actually are.

The first batteries may have been clay jars which held cylinders of iron encasing copper rods. A number of these mysterious objects were found by archaeologists in what is now Iraq. They date back around 2000 years, and reproductions of these objects can produce an electrical charge when filled with an acid such as vinegar, as they originally had been. What they were used for, though, is uncertain.

What we think of as batteries today date back just over 200 years. An Italian physicist created the first modern battery using zinc, silver and brine in 1800. Over the next hundred years, scientists in England and Europe experimented with a range of metals and other chemical compounds, and came up with a number of battery types, some of which are still used today. Petrol and diesel vehicles, for example, are started with batteries made from lead and sulphuric acid, originally invented in 1859. This lead-acid battery was the first rechargeable battery. The first alkaline batteries, the precursors of those used in many smaller devices such as television remote controls, were invented around 1900. The lithium battery, which is the one powering our electric cars, buses, bikes and scooters, as well as our laptops, phones, drones, power tools and any number of other devices, was invented in the 1970s.

All these batteries are based on the same principle – a chemical reaction is converted to electrical energy. Whatever the type of battery, whatever the chemicals inside, the same basic kind of chemical reaction is involved. This is a known as a redox reaction, and it involves the transfer of electrons, which are a tiny part of an atom with an electrical charge. We are familiar with many kinds of redox reaction, including the rusting of iron, the burning of oil and the explosion of gunpowder.

There are many types of batteries powered by many different redox reactions. These reactions are carefully controlled inside the batteries by separating the two reactive parts, known as the electrodes. But it’s also possible for the chemical reactions in a battery to get out of control. One way is a short-circuit, which happens when the electricity follows an unintended path which allows a greater rate of energy flow. A short-circuit generates heat, and is a common cause of fires.

In a rechargeable battery, the chemical reaction which provided the electricity can be reversed by applying an electrical current to the device. This can also go wrong, because if more energy is applied to the battery than can be stored, that is, the battery is overcharged, the excess energy has to go somewhere. Usually, it ends up as heat, and it can also cause fires.

I’ve always had the thought in the back of my mind that batteries are potentially dangerous. I know we aren’t supposed to throw them in the rubbish and that they contain harmful chemicals. But when I spoke to Pete Gallagher and Tom Ronaldson from Fire and Emergency New Zealand, they explained to me that the risk has changed.

To understand why the risk has changed, it helps to think back to my chunky old Nokia 5110 cellphone. The battery of that phone made up almost 85% of the phone’s weight. Sure, it lasted nearly a week, but that was because it didn’t have to do much. A modern cellphone battery is much smaller, but it’s also much more powerful, meaning it has a higher energy density.

Pete explains: “By having such high energy density and packing so much energy into a small package, they really have multiplied the battery risk. They pose a greater risk because all that energy can come out at once. You have the chemical reaction within the battery to produce electricity, but you don't want it to occur in an uncontrolled manner. By designing the batteries to produce the most energy we keep the margins very, very tight, so even the slightest change in environment can affect the internal chemistry.”

This doesn’t mean that my phone is likely to explode as I’m carrying it around in my pocket. Tom points out that lithium batteries are safe when used correctly. “It's when they're used incorrectly that they're not safe.”

This sounds simple enough, but do we understand the correct and incorrect things to do with lithium batteries?  I soon learned that I didn’t. For years, I’ve had the habit of plugging my cellphone and laptop into their chargers in my bedroom at night and going to bed. I’ve got various other devices too – a camera with lithium batteries, an e-book reader and a portable speaker. If they are running low, the chances are I’ll charge them overnight too.

It turns out I had no decent fire photos in my collection, so here are a couple of fiery flowers (image credit: Melanie Newfield)

Tom tells me that this isn’t the best idea. “We really recommend that people charge devices while they're awake and at home, especially those big lithium ion batteries, like your e-bikes and your e-scooters.”

It also matters where our devices are charged. Pete says that “A lot of people come home and the nearest power point is right by the front door, and that's where they put the bike to charge it. If that's going to be the way that you need to escape in a fire, then it’s the absolute worst place to put that bike while it's on charge. There have been a couple of cases in New Zealand and Australia where scooters caught fire in a doorway, and the person had to be rescued through the window of the apartment.”

This point is crucial. Pete tells me: “Charging safely is really really important. From all that I’ve read, about 70 to 80% of fires involving lithium batteries occur when the device is being charged. Charging seems to be the one common factor that's most influential.”

While charging is the most likely time for a battery to catch fire, this doesn’t mean that all batteries and all chargers have the same level of risk. Tom tells me about problems encountered in London, where delivery riders were getting higher capacity batteries for their e-bikes, so they could work for longer before recharging. “Because the battery wasn’t made for the bike, they were really prone to fire. The London Fire Brigade reported a number of fires from one type of battery that people were using. And that's what we see here as well, people buying different types of batteries that don't fit their devices from 3rd party retailers. And then that's just not gelling with the device. That also goes for charging units as well. It's our recommendation to only use the manufacturer's charger. That’s the safest bet.”

The situation in the UK should serve as a warning to New Zealand. There have been a number of serious fires, including one heartbreaking situation where a woman and two children were killed, which resulted from using the wrong battery or the wrong charger for an e-bike.

The other important factor in battery safety is damage. There’s no more startling example than the case of a house fire started by a dog which chewed on a battery when no humans were home. This was caught on video – I’ve linked to it here. Fortunately, in this case all the animals were able to escape, but it shows what damage to a lithium battery can do. This risk of damage is also the reason that airlines ask you to call a flight attendant if you drop your phone. Passengers have set their phones on fire by moving their seat backs and crushing their phones. And rubbish trucks have caught fire when the compactors have crushed lithium batteries people put out with their rubbish. Battery disposal and recycling is a whole separate issue I will come back to, in the meantime, the website I’ve linked to here lists places you can take old batteries.

Thinking about damage made me wonder about electric cars. How much of a risk are they when they have an accident?

You certainly don’t want to be in an electric car that catches fire after a crash, but you don’t want to be in a burning petrol car either. Both are dangerous and the only sensible thing to do is to get as far away as possible as fast as possible. The difference is in how easy, or difficult, the fire is to put out, Pete tells me. “With a petrol powered vehicle, even if it was blazing, we could effectively extinguish it in 15 minutes, and the road could be open half an hour later. That's not going to happen with an electric vehicle that's on fire.”

The problem goes back to the point Pete made about batteries having tight margins around the conditions which are safe. Once the battery has heated up, the chemical reaction gets out of control. The batteries in vehicles (including e-bikes and scooters) are made up of multiple cells. If an individual cell catches fire, the heat can compromise surrounding cells, and they catch fire too, in a process known as thermal runaway (for an explanation, I’ve linked to a video here).

Pete explains: “The most appropriate method to stop this is to cool the battery. If we reduce the temperature, that breaks the thermal runaway because we're taking the thermal part out and the reaction stops. But of course the batteries are impact protected. So getting water to a battery to cool it is difficult. And cars are made out of steel, or a large percentage of it is steel, so that acts as a heat sink as well. So we're trying to cool the battery. But we're actually cooling all the steel work associated with the car as well. It can take several hours and large amounts of water. So road users can be disadvantaged because we may have to close the road for several hours.”

However, there is more to risk than simply the size of the harm, as I explained a couple of weeks ago. Tom tells me that, so far, they aren’t seeing many fires with electric vehicles. Is that simply because there aren’t so many of them on the road? Perhaps, but there is now a considerable amount of data building up from overseas, particularly Europe. What they are seeing is that electric cars are much less likely to catch fire than petrol or diesel cars. Figures from Sweden suggest cars with internal combustion engines are 20 times more likely to catch fire than electric cars – this is once they’ve accounted for the fact that there are still fewer electric cars on the road.

There’s one other point about lithium battery safety that is worth knowing. Pete points out that a lithium battery fire is not the kind of fire we are used to. “These types of fires, these are chemical fires that are totally different to burning newspaper or burning twigs, or even an oil fire, say, if you're cooking and it’s caught fire. It's absolutely totally different. These are very, very hot, very intense fires, and because of that they have the ability to set fire to things next door to them which you wouldn't normally think are flammable.

“Anywhere you're charging lithium devices, there should be a smoke alarm in that room. The white smoke that's given off very early on is highly toxic. As soon as that smoke alarm alerts you, you need to be on your way out of the building. There's no safe way to handle a device once it starts smoking. I've heard from overseas experience that people have tried to pick up smoking cell phones and smoking small electronic devices, and it's just ended up with them being injured. The best thing to do is just get out of its way.”

Right now, it’s not necessarily easy to hear about the downsides of lithium batteries. I know I’m not giving up my cellphone, laptop, camera, portable speaker, e-book reader, wireless mouse, toothbrush, power banks, cordless drill, sander… I’ll be honest, I don’t have the faintest idea how many lithium batteries I’ve got in my house. It’s a lot.

It’s also not a great time to be talking about the risks of electric cars, buses, scooters and bikes. After all, burning fossil fuels has been catastrophic for the planet and electrification is part of the solution.

The risks associated with lithium batteries aren’t a reason that we shouldn’t use them. The point is that lithium batteries are a new technology, and most of us don’t understand the risks and how to manage them. Pete makes a point which is crucial here.

“We often don't take things seriously unless there's a disaster. Sadly, that's the nature of the business that I'm in. When we look at legislative changes to keep people safe in buildings, for example, that's occurred as a result of tragedies. We need a mindset shift to say let's look towards the future. What's the potential here? How can we stop it reaching a tragedy before we start acting? With lithium batteries, we've got that chance. We have got a chance to turn it around now and start looking forward. We know that there's a risk with these things. We just need to educate people better about how to manage that risk.”

Managing the risk of lithium batteries doesn’t only fall to individuals, of course. There are wider questions about how they should be regulated. However, individual actions do affect the risk. For a summary of how to keep yourself and your family safe, here’s some more information from Fire and Emergency New Zealand.

Lithium-ion battery safety | Fire and Emergency New Zealand

Image credit: Melanie Newfield