Hot Feet from Hoverboards

Not long after my university went back in session in January, I saw a couple of young men tooling along a sidewalk on campus on two-wheeled things that looked like Segways, but without the vertical handle.  They turned out to be hoverboards, a gadget that packs two high-power motors, some gyros and accelerometers, some electronics, and high-capacity lithium-ion batteries into a space smaller than a skateboard.  Evidently if your balance is good enough and you can pay the roughly $300 and up the thing costs, you can have the sensation of standing on your own private moving sidewalk.  But a few users have had a more exciting time with their hoverboards than they bargained on:  their units have caught fire.  One family in Petaluma, California reported that after fifteen minutes of charging, their daughter's hoverboard "exploded" into flames, making a noise like a small bomb and sending burning embers around the room.  Fortunately, someone was around to put out the fire, but a hoverboard was possibly responsible for a house fire in Santa Rosa that did extensive damage and killed two of the family's pet dogs. 

Also in January, the U. S. Consumer Product Safety Commission (CPSC) launched an investigation after receiving more than 40 reports of fires involving these devices.  Although many of the units were purchased through Amazon.com, evidently for Christmas presents, Amazon has since quit selling hoverboards and carries only accessories for them now.  But you can still find independent sellers online who carry the things, along with answers to questions like, "Will my hoverboard catch fire?"

All sources I consulted agree that the fire problem is traceable to the lithium-ion batteries in the units.  The motors can draw as much as 300 watts apiece, and no other type of battery currently available on the consumer market can supply that much power and still fit in a hoverboard that doesn't weigh more than the rider.  Lithium-ion battery technology is a carefully calibrated technological dance along the line between success and failure, where failure is usually spectacular.  Charging the batteries too much can cause the already pressurized cell to rupture, it can heat the thin insulating separator between the cell's cathode and anode to cause a short circuit and further heating, and can lead to the lithium compounds inside the cell to burn vigorously when exposed to air. 

Over a dozen different brands of hoverboards have come on the market, and some companies may be using inferior-quality batteries that are especially prone to catch fire.  In reaction to the posting of vivid videos of hoverboard fires on Youtube, some companies have started boasting that they use only genuine Samsung or other name-brand batteries.  But they still advise against leaving the room while a hoverboard is charging, just in case something goes wrong. 

Fortunately, no human has died as a result of a hoverboard fire.  And considering the already rather self-limited market for these things—you have to be young and flexible enough to both balance on one and survive any falls, plus be able to afford to blow $300 or more on a thing you may never learn to use—hoverboard fires don't rank up there with issues like the onboard lithium-battery fires that plagued the Boeing 787 back in 2013 and caused a couple of potentially deadly incidents before the fleet was grounded to fix the problem.  Still, the fact that we are aware of at least 40 fires caused by hoverboards shows what can happen when a flock of fast-moving manufacturers, probably all based in Asia, try to exploit a short-fuse market opportunity without taking the time and effort to do thorough safety testing.

Some would call for the heavy hand of government regulation to make sure that all consumer products pass standardized safety inspections before they can be sold.  The private Underwriters Laboratories, which is responsible for the "UL" symbol borne by many consumer products that pass its rigorous safety tests, has been trying to find a hoverboard that is worthy of the UL label, but so far all the ones they have tested have flunked. 

What we see in the hoverboard situation is how the rapid pace of information exchange on the Internet has dealt with the problem while the government is still pulling its pants on, so to speak.  As I mentioned, somewhere between January and today (March 13) Amazon quit selling hoverboards and offered a money-back exchange for those already sold, no questions asked.  Anyone googling "hoverboard fire" can find a lot of privately posted videos of smoking hoverboards, which the younger population is sure not to miss.  And many of those who are still selling the units are using the fear of fires as a selling point for the higher-quality name-brand batteries they use in the particular models of hoverboard they sell. 

Of course, even name-brand batteries can catch fire if abused, and there are warnings about not subjected the batteries to excessive shocks.  That would seem a little hard to avoid in the case of a consumer product that is likely to be flipped around underfoot by the user, at least a few times, until he or she gets the hang of it.  And who knows?  maybe hoverboards will form the basis of a new sport.  San Marcos, the Texas town where I live, happens to be a hotbed of activity for, believe it or not, unicycle football.  There are regular tournaments downtown and clubs and the whole bit.  Anybody who can play unicycle football isn't going to have much of a problem riding a hoverboard, and keeping it protected from undue shock and vibration.  Watch out, unicycle football.  Hoverboard football may not be far behind.

Eventually, the CPSC will come up with conclusions from its investigation, but by then hoverboards may either have become a routine part of the way we get around, or a forgotten fad like the Hula-Hoop.  The worst that you could do with a Hula-Hoop was to throw your back out.  But if you did, you probably shouldn't have been fooling with the thing in the first place.  The long-term solution is to find a battery technology that isn't as much like playing with fire as lithium-ion batteries are.  In the meantime, enjoy your hoverboards, but don't leave them alone when they're charging.  You might be in for an unpleasant surprise.

Sources:  I referred to a couple of reports on KGO's website (the ABC-TV outlet in San Francisco) at http://abc7news.com/news/childs-hoverboard-explodes-catches-fire-inside-petaluma-home/1174234/and http://abc7news.com/news/hoverboard-likely-sparked-bay-area-house-fire-that-killed-dogs/1166917/.  The information about UL and hoverboards is from the Chicago Tribuneon Feb. 23, 2016, at http://www.chicagotribune.com/business/ct-hoverboard-testing-ul-0224-biz-20160223-story.html.  I also referred to a story posted on the CBS News Interactive site www.cnet.com on Jan. 20, 2016 at http://www.cnet.com/news/feds-urge-you-to-buy-fire-extinguisher-with-your-hoverboard/and the Wikipedia article on lithium-ion batteries.  My blog on the Boeing 787 battery fires appeared on Jan. 28, 2013 at http://engineeringethicsblog.blogspot.com/2013/01/boeings-787-battery-eggs-all-in-one.html.

Correction:  

--> In an earlier version of this article, I referred to Underwriters Laboratories (UL) as "insurance-company funded."  That is not correct.  UL (LLC) is a private for-profit company as of 2012, and presumably makes money by charging companies who want the UL label for its certification services.  And while it is still true that no hoverboard has passed the requirements for UL certification, the organization has only had a month or so to start the process, and so it is possible that at least one such device will eventually pass.  I thank Brooke Higginbotham of UL for this information.