In big cities packed with commuters, hoverboards — the latest must-have gizmo —  seemed ideal for getting around, but the pricey toys have proven to be little more than a nuisance.

Because they can’t be registered with the Department of Motor Vehicles, the devices are banned on New York’s sidewalks, with violators facing steep fines. In the District, they’re prohibited on sidewalks within the Central Business District — with the exception of areas monitored by U.S. Park Police, such as the sidewalks running along Pennsylvania Avenue near The White House and the Capitol, according to the District Department of Transportation. In London, it’s illegal to ride them in public.

What happened when I tried to commute to work on a ‘hoverboard’

Now the season’s hottest toy — one was sold every 12 seconds on Cyber Monday— has come under fire due to reports that faulty batteries have led them to spontaneously combust. The Consumer Product Safety Commission has scrambled to investigate, aiming to issue guidance on the products — electric scooters that don’t actually hover — before the toys can be given as Christmas gifts. If the commission doesn’t act quickly, the chairman said in an interview Wednesday, the number of cases could balloon as the toys are unwrapped en masse.

In a Gaithersburg, Md., bedroom last month, one rolled into a mattress and set it aflame. The wheeled, self-balancing scooter had been charging. There were no injuries, but from the pictures you might think that a small bomb had exploded. It caused about $5,000 in damage.

The devices have been blamed for destructive house fires in Lafitte, La., Chappaqua, New York and elsewhere, the Commission confirmed.

“This is a very high priority investigation and we will work around the clock to try to get answers as quickly as possible,” commission chairman Elliot F. Kaye said in an interview. “My concern is that after Christmas we will see a spike in injuries associated with fires. There’s a significant amount that will not be opened until after Christmas.”

Meanwhile, if you’re planning on toting one along on your holiday travels, don’t: The major airlines have banned them. The U.S. Postal Service has limited their shipping to ground transportation, and mega online retailer — founded by Washington Post owner Jeff Bezos — has pulled some hoverboards from its online marketplace out of caution. has stopped selling them entirely. In an email to customers shown to CNET, Amazon UK advised customers to dispose of their hoverboards, and said it requested refunds from sellers.

Already, Kaye says, the commission is investigating a dozen hoverboard-related fires in a total of 10 states. The commission has logged about 40 emergency room visits related to falls and physical accidents, “with the range of those incidents being an open head wound, fractures to the arm and hand and other trauma to the arms and legs,” he said, adding, “when there’s a fall it’s pretty serious.”

“While the fire hazard has generated significant attention, I do not want to downplay the fall hazard,” Kaye said in a statement issued Wednesday.

A hoverboard set a mattress ablaze in a Gaithersburg home on Nov. 8, leading to about $5,000 of damage. (Photo: Montgomery County Fire Department)

The issue, researchers say, involves the lithium-ion batteries used by the hoverboards. Chinese companies selling and manufacturing the budget-priced versions of the devices do not adhere to the stringent safety guidelines that would be put in place by brand-name retailers, they said. The issue tends to present itself after a few charge cycles, when one or more of the cells within the battery pack malfunctions. While smartphones tend to be powered by single cells, a hoverboard contains a mass of cells packed at a high density, according to one battery researcher, “that were probably not made with the same rigorous quality.”

And that’s before you consider that they’re being thrown around, subject to the wear and tear of owners hopping on an off the devices and scraping them against the pavement.

The Post explains why lithium-ion batteries explode

“The ones that are a bit more spectacular is when you go from a usual battery that’s fully charged, and all of a sudden you have a hard short. All the energy that’s stored in the battery is now being discharged in the battery. You have a huge amount of heat when that happens, and then heat is discharged and you have a fire,” said Jay Whitacre, a professor of materials science and engineering at Carnegie Mellon University. “It’s crazy because it’s a very small thing and it has a very fair number of batteries in it.”

He stopped short of calling it “bad design,” but said some tweaks are needed to ensure that malfunctions are contained in a sort of firewall. It doesn’t help that the online hoverboard market resembles a sort of Wild West.

Models are available on Amazon for a wide range of prices: about $500 for the Swagway X1, which was pulled briefly from the site, and $296.40 for the Hover X. Meanwhile the PhunkeeDuck, a model made famous by athletes and celebrities sells online for a cool $1,499.

Kaye said there’s no way of differentiating between models that are safe and those that are cheap counterfeits. The commission, he said, has seen multiple configurations of malfunctioning devices that make it hard to pinpoint what the exact issue is.

“There’s something going on with either the way the batteries are stacked together, or there’s some insulation missing or some aspect that is not proper,” Kaye said.

Amazon recently sent out a notice to hoverboard manufacturers asking them to “provide documentation demonstrating that all hoverboards you list are compliant with applicable safety standards,” according to seller Swagway, whose device was blamed in the Chappaqua, N.Y. fire. But Kaye said even that step would not give him confidence that the product is safe.

“There’s nothing that I’ve seen, from the way that these are being manufactured, that would give me confidence that even if someone produces paperwork that these products meet industry standards that that would be the case,” he said. “In the time that I’ve been here, I haven’t seen anything like this, where you have the pressure of the holiday season approaching and you want to get answers as quickly as possible, but the hazard is difficult to detect.”

Swagway said in a statement the removal of listings included “97 percent of the other branded hoverboards selling on the site.” Amazon did not respond to a request seeking verification for the figure.

One model that has remained on Amazon even amid the controversy is the Razor Hovertrax. And the $600 item has been the company’s hottest seller on Amazon since hitting the market late last month, said its CEO Carlton Calvin, who declined to specify exact sales figures. Calvin says his company’s reputation can bring some legitimacy to the embattled product.

“You know, young adults, with their interest in moving away from cars, picking up our adult scooters, it’s another tool in the quiver of urban mobility that I think is really interesting,” he said. “I think that the main danger of having so many copies that are just coming in directly from China, people on eBay can just order them to be shipped directly from the factory. I’m concerned that it’s tarnishing the reputation of this great invention.”

A Razor spokeswoman was more pointed in an email to the Post.

“As far as the ‘super low priced knock-offs’ go, it’s pretty obvious that ‘economizing’ at the expense of safety and performance is not often a ‘plus’ for the consumer when high-tech electronics and rider safety are involved,” she said. “Razor offers superior manufacturing capabilities, technology and also customer support and experience which few, if any, of the ‘cheap’ players can even hope to match.”

Swagway said in a statement that it had “passed all testing in adherence to government guidelines.” The company said it had sent over the required information to to get its product re-listed.

Less than two hours later, a company spokesman told the Post its product was back on the site. Meanwhile, Kaye says his sister in Connecticut purchased a hoverboard as a present for her kids. But until the commission comes to a conclusion, he said, she’s keeping hers tucked away and out of sight.

“That’s certainly a safer position to take,” he said.