"Red self-balancing two-wheeled board with a person standing on it" by Soar Boards (www.soarboards.com) - https://www.flickr.com/photos/136833700@N04/21403154443/. Licensed under CC BY 2.0 via Commons - https://commons.wikimedia.org/wiki/File:Red_self-balancing_two-wheeled_board_with_a_person_standing_on_it.png#/media/File:Red_self-balancing_two-wheeled_board_with_a_person_standing_on_it.png

Hoverboards catching fire runs risk of destroying their potential contribution to transit problems

Hoverboards have been catching fire, airlines have banned them from luggage, some retailers have stopped selling them, and the fires are starting to show up in the press.  These vehicles, “Self-balancing two-wheeled scooter” is a better phrase than Hoverboard, are an interesting new way to get around.  They’re pure electric, so no emissions, and are light enough to carry around during the day.  That’s all good right?  They’re even a potential solution for certain transportation problems.  What if they’re dangerous, however?  If they catch fire too often they’d be too risky for general use.

I don’t know the numbers – how often are hoverboards catching fire compared to fire rates of other vehicles?  But whatever the rate, these fires are bad for adoption of lightweight personal-sized electric vehicles.  (BTW, the above picture came from Wikipedia)

On the other hand, we are surrounded by devices containing lithium-ion battery packs, and while there are occasional fires, they’re safe enough we don’t think there’s any risk carrying cell phones in our pockets.  Clearly there’s no significant difference between a cell phone or laptop with lithium-ion batteries and a “hoverboard” with lithium-ion batteries.  The extremely low rate of fires in laptops, cell phones, electric cars, and other devices with lithium-ion batteries demonstrate it’s possible to build safe lithium-ion powered gadgets.

I can think of a couple questions that need to be answered:  Why do they catch fire?  What can be done to avoid a fire?  What’s the risk?  How much damage are we talking about?

Battery pack fire causes

In articles I’ve seen, the fires occur while the hoverboards are charging.  Having looked into lithium-ion battery flammability, I know this is a common failure case.  Especially for battery packs that lack battery management systems to shut off charging when the battery pack is full.

Almost every energy storage technology has failure modes that result in fire.  For lithium-ion batteries, the relative risk of fire depends on the specific battery chemistry.  Some battery chemistries are more prone to fires than others.

In late 2014 during the Apple iPhone 6 bendgate period, news came of a fellow whose iPhone 6 exploded in his pocket when he was involved in a freak accident that bent the phone.  In that case the fire was certainly caused by an induced short circuit when the phone bent in half.  That sort of scenario is similar to the Tesla Model S which caught fire in Los Angeles after crashing during a high speed chase.  With a collision and physical damage to a battery pack, it’s nearly impossible to avoid a fire.   (BTW, plenty of Model S’s, Leaf’s, Volts, etc have been in serious collisions with no fires, because manufacturers encase battery packs in strong cases which haven’t been ruptured)

In more normal scenarios, we need to be able to charge and use hoverboards, and other lithium-ion powered vehicles, without risk of fire.  A minimum requirement is for battery packs to have battery management systems preventing the cell voltage from falling too low or rising too high, both of which are failure cases that can lead to fire.

Some think another risk factor are hoverboards that don’t stand up to the rigors of being ridden, especially with the kind of tricks some do on hoverboards.  One supposes a weak case structure could buckle, causing penetration of a battery cell, resulting in a short circuit, that causes a fire.

Cheap knock-off Hoverboards the likely culprit

According to articles like this one on The Daily Beast, a contributing factor in this case is cheap knock-off hoverboards from China and an unclear situation of ownership over the technology.   A Chinese fellow living in the U.S. claims to have invented them, and was negotiating licensing rights with another fellow who also claims to have invented them.  In the meantime a flotilla of Chinese manufacturers have knocked off identical clones, but sometimes used sub-standard parts.

What’s most risky is to skimp on the most expensive part, the battery pack.   Unscrupulous manufacturers could easily use fire-prone batteries with no battery management system.   Products with cheapo battery packs, that might lack a battery management system, would be prone to fire.   I think the Daily Beast article linked above is dangerously overhyping the risk.

As I said above, if there’s no BMS there’s no protection against overcharging the battery pack.  An overcharged battery can catch fire, producing the results we’re seeing in the news now.

Recommendations

If you do experience a hoverboard fire – or for that matter a fire in any lithium-ion battery pack – do not pour water on the fire.  That just makes the fire worse.  You should also expect occasional explosions, as shown in the video below, as the fire spreads from cell to cell in the battery pack.  With luck your fire will occur outside, and you’ll be able to keep away from the fire until it burns out.  If not do your best to bring it outside, but do so with care so you don’t get burned.

At this time its wise to avoid buying the hoverboards that have junk parts inside them.   One way is to limit your purchase to reputable vendors.  Perhaps in time manufacturing standards will be applied to these vehicles, and it’ll be safe to buy from the cheapie vendors.  At the moment, given the number of fires, it’s best to skip past the cheapie vendors.

But even that’s not a certainty, given a recent fire involving a Swagway hoverboard.  That brand is thought to be reputable.

Something to look for is compatibility with relevant standards:  UN 38.3 (battery), UL 1642 (battery), and UL 60950-1 (charger)

Physical safety

There’s another risk, besides the fire risk, with hoverboards.  This is — how to avoid falling off the thing, and getting injured, or worse falling in front of a larger vehicle and getting crushed.

In this case the risk is similar to the risks with riding a bicycle or kick scooter.  That is, except for the fact that hoverboards don’t have anything to hang onto to assist with preventing a fall.  It’s best, therefore, to spend some time in a safe location acquainting yourself with riding safely.  Don’t just jump on one, learn how to safely get on and off, and before heading out into traffic spend awhile experimenting so you know how to handle yourself.

Airline bans

Why are the airlines banning hoverboards from aircraft?  Why are postal services banning hoverboards from air shipments?  This is due to a United Nations regulation concerning air shipment of lithium battery packs.

Over the years there have been a few cases of lithium battery pack fires on aircraft.  A couple cargo aircraft were destroyed due to such fires, until the UN stepped in (years ago) and banned the shipment of large battery packs.  A problem is that the manufacturers aren’t clearly labeling hoverboards to show the battery pack size.  That means it’s difficult for airlines or air shipping companies to know whether the battery pack in a given hoverboard is small-enough to fit the regulations or not.  And, given the fires currently happening it’s best if these companies err on the side of safety.

As much as a hoverboard is begging to be carried in luggage on a trip, we don’t want an airliner to go down in flames because of a hoverboard fire.

Hoverboards have great potential if used wisely

Vehicles like these hoverboards have great potential as a transportation alternative.  They’re small, light, no emissions, and offer a way to move ourselves from place to place with very low energy expenditure.  They’re easy to carry on board a bus or train, making them a feasible solution for “last mile” intermodal transit problems.  That is, you could ride one to the bus station, carry it on the bus, then ride it from the bus stop to your home.

With luck the companies involved will recall these products, the dangerous ones will be taken out of circulation, the engineering fixes put into place to fix the problem, and the resulting hoverboards will be safe and the fire issue will fade into the past like the laptop fires of a few years ago.

 

 

 

About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.
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About David Herron

David Herron is a writer and software engineer living in Silicon Valley. He primarily writes about electric vehicles, clean energy systems, climate change, peak oil and related issues. When not writing he indulges in software projects and is sometimes employed as a software engineer. David has written for sites like PlugInCars and TorqueNews, and worked for companies like Sun Microsystems and Yahoo.

One Comment

  1. Thank you for this useful information.
    More reasons to be looking into Lithium-ion batteries replacements.

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