There are two things common among the 12 hoverboards that exploded and burned in the U.S. These gadgets had lithium ion batteries and were made in China.
The U.S. Consumer Product Safety Commission (CPSC), however, has yet to identify the cause behind the explosions. CNET notes that the fires caused by the hoverboard explosions occurred in different circumstances. Scott Wolfson, spokesman of the commission, says a "very thorough science-based investigation" is going on.
Some of the boards exploded during the charging, others while it was moving and in one instance, while just idle near a Washington shopping mall kiosk. Outside the U.S., hoverboard explosions have also occurred in the UK and Hong Kong. There is no particular brand of hoverboard susceptible to explosion.
The tech website points out that advice by authorities to use only the charger that comes in the box is almost next to useless since plugs of hoverboards are different from other devices, removing the possibility of using another charger for a different gadget. Overcharging as a reason behind the explosions is also unlikely since most of modern devices, when fully charged, automatically shut off the electricity's flow.
CNET notes that majority of hoverboards use lithium batteries that are highly flammable. When a short circuit occurs, such as when the plastic cover of the battery is punctured, its liquid electrolyte could heat up and result in an explosion. The small sharp particles inside a defective battery could also puncture the plastic that separates the battery's negative and positive sides.
"When this happens, especially when the batteries are charged, a lot of heat is generated inside the cells and this leads to electrolyte boiling, the rupture of the cell casing, and then a significant fire," Wired quotes the explanation of Jay Whitacre, materials science professor of Carnegie Mellon University.
Whiteacre adds that quality and consistency of batteries made in China, which hoverboards use, is not as good as those manufactured by tech giants such as Samsung or LG. Although not knockoffs or copies, the Chinese Li-ion batteries are mass-manufactured cells that risk fires on the "hot" holiday gift.