Vehicle fires: What’s more dangerous - an EV or a petrol car?

When I saw a Nissan Leaf cut in half at the Christchurch Innovation Expo, my first thought was: That’s one way to keep the batteries cool on an older EV.

In fact, it wasn’t extreme EV ventilation but an EV City initiative to help emergency services train for electric vehicle fires.

EV fires are happening, from an electric vehicle that caught fire in the garage of a Pakuranga Heights home last month to the spectacular Tesla blaze on Auckland’s Harbour Bridge in March.

But in fact, statistics indicate EVs are actually much less likely to be involved in a fire than a car powered by a petrol or diesel internal combustion engine (ICE).

Ed Harvey, CEO of Christchurch-based electric charger maker Evnex, points to a recent study by a US insurance company that found:

• 1529 petrol vehicle fires per 100,000 sales
• 25 electric vehicle fires per 100,000 sales

And when EV fires happen, they’re almost never the result of a crash. “It’s not zero, but the possibility of your EV’s battery catching fire as the result of a collision is remote, comparable to the risk in an internal combustion-powered car,” a Wall Street Journal analysis said. (An example of it not quite being zero occurred in Nelson in October last year, when Fenz was called to a fire after a Nissan Leaf’s battery array was punctured by a fence post).

“There are very few incidents, but you read about every one of them,” Harvey says. (It should be pointed out that ICE vehicle fires have got a bit of press just over the past few months, too, including this June blaze on Auckland’s Southern Motorway, this one on the Northern Motorway, this September fire that blocked the Waterview Tunnel and this fire on a North Shore street).

Battery packs - in silver - exposed in the Leaf tear-down. Photo / Chris Keall

For additional context, Fenz says that last year, emergency services attended a total of 1875 vehicle fires. Fenz doesn’t keep a breakdown of ICE versus EV fires although “work is being undertaken to change this,” a spokeswoman says.

But even if all 36 lithium-on fires for the year were vehicle-related (they aren’t some involve e-scooters, e-bikes or other lithium-powered devices), it would still be 1.9 per cent of fires at a time when EVs accounted for just under 3 per cent of NZ’s fleet.

The manual disconnect for the Leaf's high voltage systems. Photo / Chris Keall

And despite the rise and rise of EVs (or perhaps we should say partly because of it, in keeping with Harvey’s mythbusting take), the total number of vehicle fires has actually declined from 2103 in the year to June 30, 2019 to 2078, 2011, 1980 then 1875 over the subsequent annual reporting periods.

EV makers are also getting better and better at thermal management, Harvey says, with the primary aim of better managing the impact of fast charging on battery life than fires per se. There have been glitches along the way, including Jaguar’s recall of its I-Pace EV in June this year over a thermal overload issue - albeit one that has not caused any incidents in NZ or globally.

But despite the lower risk, when they do happen an EV fire can take more than 10 times as much water to put out compared with a fire in a petrol or diesel car, Fire and Emergency NZ says. A petrol or diesel car can take 2000 to 4000 litres to extinguish, and an EV 25,000 to 50,000 litres.

With an EV fire, there’s the first issue of “thermal runaway” - when a single cell in a battery overheats and a chemical chain reaction causes a sudden, immense amount of heat that ignites other cells. The batteries can also reignite after several days. (One of the main reasons for the cut-in-half EV is to show fighter fighters where to manually disconnect the car’s high voltage system - see the clip above).

And Fenz has been on a push to educate people that the rising popularity of lithium-ion battery-powered light vehicles, from EVs to e-scooters and e-bikes, plus various other gadgets, has heightened the risk of fires, usually tied to overheating. Fenz gave the Herald the following stats.

• From 1 January to 4 September 2023 there were 52 potential lithium-ion battery-related fires recorded
• From 1 January to 31 December 2022 there were 36 potential lithium-ion battery-related fires recorded

They are listed as “potential” lithium-ion fires because “we do not currently collect data in a way that allows us to easily identify the exact type of battery causing the fire”.

The cutaway Nissan Leaf that was on display at the Christchurch Innovation Expo. Photo / Chris Keall

Neither has Fenz released a breakdown of the vehicles or gadgets responsible for each fire. There can even be a mix-and-match.

Fenz recently said that since 2019, there have been 15 recycling truck fires suspected to have been caused by discarded lithium-ion batteries.

New Zealand encourages lithium-ion battery recycling but doesn’t make it compulsory, like across the Tasman (one of the reasons that New Zealand e-waste pioneer Mint Innovation opened its first plant in Sydney, with no immediate plans to build one at home).

Fenz tips for safe lithium-ion battery safety

I have to say when I recently acquired an e-scooter, my default would have been to plug it in and charge it overnight. Luckily, the chap who handed it over pointed me to the documentation that explained that was a no-no, given overcharging can cause overheating. Instead, I set an alarm for four hours after plugging it in.

Fenz advice hits a range of related themes:

• Only use chargers that are supplied with the device, or certified third-party charging equipment that is compatible with the battery specifications. Using chargers with incorrect power delivery (voltage and current) can cause damage to the battery, including overheating, which can lead to fires
• Don’t leave batteries or devices charging unattended overnight. Once the indicator shows that a device or battery has been fully charged, disconnect it from the charger
• Only purchase and use devices and charging equipment from reputable manufacturers and suppliers
• For smaller devices, such as tablets, laptops and phones, do not charge these under a pillow, on the bed or on a couch – they can overheat and cause a fire.
• Never store or leave batteries or devices in areas where they can be exposed to heat or moisture. Do not leave devices in direct sunlight or in parked vehicles where they can quickly heat up

If the device or battery starts to smoke or emit flames

• Battery gases, vapour and smoke are highly toxic and flammable and must not be inhaled. If anyone has been exposed to battery fluids, debris, smoke, vapours, or flames, seek urgent medical assistance
• Burns should immediately be treated with cool running water for 20 minutes
• Burns larger than a 20-cent coin require emergency care.
• Call 111 and wait in a safe location for firefighters to arrive

If a small battery or device such as a phone or tablet starts overheating

• Unplug it from the power outlet if it is charging.
• If possible, move it outside, away from any flammable material and windows or doorways
• Small devices can be dropped into a bucket of water if this can be done safely
• If using a fire extinguisher (dry chemical powder or carbon dioxide), only attempt to from a safe distance, away from any smoke or vapours
• Water and fire extinguishers may be used to prevent the spread of fire but are not likely to fully extinguish a lithium-ion battery fire
• Call 111, even if you no longer see visible smoke or flames. There is a chance that the battery could reignite if it has not been sufficiently cooled.

Source / Fenz

Chris Keall is an Auckland-based member of the Herald’s business team. He joined the Herald in 2018 and is the technology editor and a senior business writer.