What Are Hoverboards And Why Do They Explode?

Popular Science investigates the self-balancing scooter

Beware of what you buy this Christmas—it could blow up in your face. Hoverboards, more accurately described as self-balancing scooters, are one of the most popular holiday gifts this year. Ebay reportedly sold more than 5,000 units on Black Friday and claims to have sold one hoverboard every 12 seconds on Cyber Monday.

But there’s an increasing concern about the safety of these vehicles. There are already thousands of hoverboard wipeout videos available on sites like YouTube, and in many cases, the personal vehicles have caused serious injury. In more extreme cases, cheaply made hoverboards have exploded and caught fire, forcing Amazon to stop selling specific models and Overstock to discontinue all sales. London and New York City have taken measures to curb the use of hoverboards on city streets and sidewalks. So we thought it was a great time to break down the hoverboard craze. Here’s everything you need to know about shopping for hoverboards during the holiday season:

What is a hoverboard?

Technically, a hoverboard is a levitating platform (that looks like a skateboard without wheels) that can be used for personal transportation. The term was invented for the movie Back to the Future II, where protagonist Marty McFly travels into the future to discover that teenagers are riding on levitating boards without wheels. Although self-balancing scooters don’t actually hover, people have adopted the term “hoverboard” as a more colloquial way to refer to the vehicles—mainly because it sounds cooler.

How do they work?

Self-balancing scooters have a few basic components: a gyroscope to determine the pitch or balance of the machine, motors that keep the board balanced and move it forward, microprocessors to manage power output to the motors, and large batteries to fuel the device.

The most important function of a self-balancing scooter is (you guessed it!) remaining upright. In order to do this, microprocessors in the vehicle monitor the direction a rider is leaning. The gyroroscope, also connected to the microprocessors, helps gather information about the tilt of the board. Motors inside the board change power output to keep the rider balanced. Every self-balancing scooter is different, meaning that each one uses a different battery, set of microprocessors, and motors.

Why are they so popular now?

You can thank Justin Bieber. And Wiz Khalifa. And Nick Jonas. And Kendall Jenner. And Skrillex. And all of the other celebrities that have been seen riding them down in public and in their homes.

One of the first widely publicized instances of someone riding a hoverboard was in June, when the Cleveland Cavaliers lost the NBA Finals. The team’s shooting guard J.R. Smith, known for his outlandish behavior off the court, was seen riding one away from the arena and was quickly turned into a meme.

It wasn’t until months later, in August, when Wiz Khalifa was arrested at Los Angeles International Airport that the phenomenon was solidified. Shortly after, celebrities were spotted riding hoverboards in many high profile places.

Are hoverboards legal?

Not everywhere. The New York City Police Department declared hoverboards illegal and warned people that they could be met with fines and other penalties if they’re caught riding them in the street. “Be advised that the electric #hoverboard is illegal as per Admin. Code 19-176.2,” tweeted the NYPD’s 26th precinct from their public account in mid-November. Although the tweet was deleted shortly after it was posted, the NYPD later confirmed that hoverboards are illegal to ride in New York City.

The United Kingdom has taken a similar approach. Self-balancing scooters and other motorized transporters are banned from sidewalks. The ruling is part of the 1835 Highways Act, which prevents people from using the sidewalk to lead or drive any horse, cattle, or carriage of any description. There are also laws in place that prevent people from using self-balancing scooters on public roads in the UK. Any motor vehicle used on a public road requires the user to be licenced and insured, and the vehicle must be registered. Unfortunately for anyone in the UK, you can’t register your hoverboard.

Both New York City and the United Kingdom are using similar interpretations of the law to limit the use of self-balancing scooters in public areas. The reason is that hoverboard riders will disrupt the flow of traffic if they’re using them on sidewalks (similar to a bicycle on a sidewalk or any other large vehicle). These government agencies are also preventing people from riding hoverboards in the streets because they can’t be registered, licensed or insured. So, in short: The only place you’re really safe riding a hoverboard is on private property.

You also can’t bring a hoverboard onto an airplane. United, American, and Delta Airlines have banned the scooters are flights, even as checked luggage. The high-watt lithium batteries used in hoverboards can start a fire in a plane’s baggage compartment according to the Federal Aviation Administration. According to a CBS report , the U.S. Consumer Product Safety Commission is investigating 10 incidents of hoverboard fires in nine states.

Why do they explode?

In most cases, a hoverboard explodes because it comes equipped with a faulty battery. There is a huge difference in the price and quality of different hoverboards on the market. Until Amazon’s recent decision to ban several popular models of hoverboards over safety concerns, you could find models priced between $300-$700. And there are even more expensive ones, such as the PunkeeDuck for $1500.

As you can imagine, the low-priced versions of these hoverboards aren’t built as well as some of the higher end versions. Buzzfeed News reported on the factories in China that quickly jump on these consumer trends without much quality control. Many of these factories that start shipping hoverboards without any quality control can actually be shipping a dangerous product.

Exploding batteries are actually nothing new for consumer electronics: smartphones, laptops, electric cars, and more have all had numerous reports of battery explosions. In most cases, the heat-sink systems or cooling components included in the device aren’t enough to keep the operating at a safe temperature. In the case of a vehicle like a hoverboard, the batteries are so large and powerful that the resulting fires can be large enough to burn a house down.

So how cautious should you be? Consumer affairs site Best Reviews is encouraging people to refrain from purchasing hoverboards, citing the uncertainty around the safety of various models. “For the time being, we are not recommending any hoverboards until they are proven to be safe,” said the site in a recent blog post. Or as we like to say: ride at your own risk.