Lithium-ion battery fires are being caused by DIY e-bike alterations inspired by YouTube, an inquest has heard.
NSW Deputy State Coroner Kasey Pearce was overseeing the inquest in Sydney that was focused on the specific circumstances of four fires, two of which were fatal.
Videos from testing labs have been admitted into evidence, showing how hot and volatile the fires can get.
At least two of the fires, including a deadly blaze in Lake Macquarie, involved "backyard" repair jobs of e-bike batteries.
Judge Pearce's focus is on so-called micro-mobility vehicles, including e-bikes, e-scooters and hoverboards.
The inquest began in December and resumed this week.
Today, counsel assisting the coroner, Ann Bonnor, asked about repairs done by unlicensed people.
Andrew Low from Fire and Rescue NSW's Fire Investigation and Research Unit told the inquest that too often fires had been linked to homemade repairs or battery re-builds with parts bought online.
"There are backyard operations, they have soldering irons and they purchase things off eBay to do repairs," he said.
"Their exact motivations, I don't know, maybe whether to get more power, I am not really sure."
He said he had been to eight lithium-ion battery fires and most were linked to unauthorised repairs or people adding batteries to existing packs.
"I have been to a few where it has been evident that they have made some non-manufacture changes to batteries," he said.
His evidence echoed testimony given by Fire and Rescue Assistant Commissioner Brendan Cox in the initial hearing.
He said backyard repairers, purporting to be experts, had been linked to blazes in New South Wales and Victoria.
He said it was "unregulated and dangerous work, often sought after by people wanting to save money".
Fleeing fire
The first fire happened in short-stay accommodation at Cabarita Beach in Northern NSW in September 2023, a day after a man picked up his repaired e-bike battery.
He suffered severe burns to 40 per cent of his body, but survived.
In the second blaze being examined, a food delivery driver was injured in December 2023 when his second-hand e-bike battery exploded in his bedroom in the inner-Sydney suburb of Annandale.
Mazharul Haque Shohan, who suffered burns to 20 per cent of his body, gave evidence to the inquest today.
Mr Shohan said he thought he was dreaming that night, before fleeing while on fire.
"I woke to a huge sound, I thought I was dreaming," he said.
"It was a matter of five seconds of my life, there was a really big bang and things were shaking."
He said there were flames and extra heat and he knew he had been burned.
"There were instant flames with the bang. The bang came out with a lot of sparks. Black smoke and smells," he said.
"It felt like it was blasting a couple of times."
Two other men fled the unit.
Mr Shohan told the inquest the month before he had his e-bike battery stolen, so he bought a replacement.
Explosions and death
The last two fires were fatal.
In February 2024, two women died in a two-storey townhouse at Teralba, south of Newcastle.
The inquest heard a "backyard" repairer inserted mismatched pins and pierced an e-bike battery's casing before it exploded.
Patricia Kerr and Therese Harris were killed.
The inquest has heard temperatures could reach 900 degrees Celsius within minutes when lithium-ion batteries exploded.
The inquest heard battery cells could also be ejected from a battery pack up to 40 metres.
The fourth and final fire involved a battery charging 30 centimetres from the foot of a delivery driver's bed in Sydney last year.
The inquest heard he suffered incineration injuries, dying at the scene.
Fire Rescue NSW data tendered in court has said lithium-ion batteries caused about six fires in NSW per week.
The inquest is due to run until the end of next week.
