A family whose electric bike’s battery exploded in their garage are counting themselves lucky the house did not burn down after they dismissed the “loud bang” as owing to the notorious Wellington winds.

The family had been watching a movie on Friday in their Wellington region home when they heard the bang, which they did not think much of due to the high wind warning in the area.

“We thought, ‘Hey, you know, something banged outside, no big deal’. Now we realise that was the battery exploding,” said Vanessa, who didn’t want her surname used.

The battery exploded while the family were watching a movie.

About 15-20 minutes later, they started getting ready for bed when they realised something was wrong.

“We walked out into our hallway and smelled this horrific smell, and saw, like, a haze of smoke in the hallway,” Vanessa said.

“We opened the internal door [to the garage] and it was just thick with smoke, and there was a fire.

“My god, I’ve never seen anything like it.”

Vanessa said the flames were about waist-high and about half the width of the bicycle. They began throwing towels and water on to the blaze and were able to put it out themselves.

The smoke poured into the house, setting off the alarms.

“It’s an electrical smell. It’s the most vile, disgusting smell, [and] went through the whole house,” she said. “You could feel it in the back of your throat, which was just foul.

“The only thing that really saved us from the house catching on fire, luckily, was the half-concrete wall ... We’ve got fire marks all the way up it.

“Had that been Gib, that would have been the house.”

She said everything in the garage was covered in a layer of soot. All they could talk about as they cleaned up was how lucky and grateful they were it hadn’t managed to spread to the rest of the house.

The family did not call 111 as they were able to put out the fire quickly, but Vanessa said she thought she likely should have, even in the aftermath. She wondered how many similar fires went unreported.

There were “so many what-ifs”, including what would have happened were they asleep, or away. Vanessa and her partner also had her elderly mother and two teenagers sleeping in the house that night.

Thankfully, the fire did not spread to the rest of the house.

The bike which caught fire was a high-quality mountain bike which had been converted to an electric bike, and was charging at the time of the explosion.

Vanessa was now questioning whether they should keep an electric skateboard they also own, and said they now had rule that iPads and other devices were not to be charged overnight.

The experience has caused the family to make other changes, including installing a smoke alarm in the garage and making sure they had other fire-suppressing equipment such as an extinguisher.

“It was a shock, and just a big wake-up call.”

In July last year, a man was critically injured when an e-scooter he was charging in an apartment exploded.

The incident prompted a warning from Fire and Emergency New Zealand (Fenz) about the dangers of lithium-ion batteries.

Risk reduction and investigations manager Pete Gallagher said Kiwis had little understanding of the risks of the batteries and how to use them safely, despite them being “in everything”.

“We use them in our daily lives, from cellphones to power tools, to laptops and computers, to e-scooters and e-bikes, through to electric vehicles.”

The batteries are most at risk when they get too flat or are left connected to a charger longer than necessary. Gallagher said the batteries liked to be “stable”, so dropping below about 20 per cent of charge could present a risk.

“If the batteries are abused, if they suffer some physical damage, if they’re dropped, that can also cause that chemical reaction inside the battery to start. It generates more and more heat. The heat can’t escape and they burst into flames.”

Fenz recommended people store and charge e-scooters and e-bikes somewhere other than inside their homes, as they were larger and could potentially cause more damage if they caught fire than a cellphone would. But if people could not store them elsewhere, Gallagher recommended putting them in an area with a smoke alarm, and not near an exit point.

Melissa Nightingale is a Wellington-based reporter who covers crime, justice and news in the capital. She joined the Herald in 2016 and has worked as a journalist for 10 years.