Blowing Up Hoverboards on Purpose
A peek behind the scenes at UL’s hoverboard safety testing
Things are getting explosive at UL, the company that develops safety standards for products and evaluates, tests and certifies them.
Hoverboards burst onto the market in 2015 — and proceeded to burst into flames, in dozens of headline-grabbing cases. Retailers yanked the products from shelves. Airlines banned them from planes, and more than 30 colleges banned them from campuses.
In early February, UL announced it would start certifying these self-balancing scooters, focusing on the safety of their electrical systems, batteries and chargers.
The Consumer Product Safety Commission has urged manufacturers to seek UL certification, saying hoverboards are unsafe until they meet safety specifications because of “an unreasonable risk of fire to consumers.” The agency also warned it could recall them.
UL recently pulled back the curtain on what those hoverboard safety tests will involve.
The blunt nail test
(Photo: Courtesy of UL)
UL uses this to test a single lithium-ion cell. While the blunt nail test is not part of the new standard, it demonstrates what could happen if a single cell fails due to a short circuit. A properly made battery would have the right circuit protection.
A lithium-ion cell is “about two inches long and looks like a AA
John Drengenberg, consumer safety director for UL. “That one
cell goes into a battery pack with 20 to 24 of them, and that battery pack goes
into the hoverboard.” This test shows what would happen if there was an issue in just one of those many cells.
The test simulates a short circuit in the battery. “We want to make sure we can get the cell to malfunction. Cells malfunction because of impurities in the battery — in the cell itself. Those impurities are random, manufacturing errors or lack of quality. But in order to evaluate the enclosures, we simulate the malfunction,” Drengenberg says.
“The nail makes the battery spark and pop. Some of them go off like firecrackers. What we’re looking for is that the battery enclosure is built in such a way that it will vent that pressure without the big explosion and rapid fire,” he explains.
The drop test
Hoverboards are dropped repeatedly from a height of one meter, or about three feet — about the height at which someone would carry it, plus a little bit, Drengenberg says.
“This traces back to normal use. If you’re carrying your hoverboard and it slips out of your grasp, will it be safe? Or will it dislodge the battery pack internally or crack the enclosure?” Drengenberg says. “We drop it three times on three faces – the wheel side, the top side, the bottom side.”
The submersion test
“We dip hoverboards in water up to the bottom of area where your feet go. People will ride in the rain or through puddles. So we test it in the water for five minutes,” Drengenberg says. After the submersion test, UL does other tests to make sure there are no internal electrical short circuits and nothing is overheating as a result of water exposure.
The Bunsen burner test
(Photo: Courtesy of UL)
In this test, a lithium-ion cell from a hoverboard battery is heated over a 1,000-degree F Bunsen burner flame for several minutes. The battery and the flame are surrounded by a screen on all sides.
“In just 10 or 15 seconds, the battery is so hot it just explodes. What we’re looking for: Will it project pieces through the screen, which is one foot away from the battery? If any piece that’s projected from that exploding cell penetrates the screen, it’s a failure.”
Better safe than sorry
While some of these tests may seem extreme, there’s a reason for that. "If you think how kids treat these things, throwing them on the floor like a skateboard, banging up curbs or leaving them out in the rain, then you can see why these tests are necessary,” Barbara Guthrie, UL’s chief public safety officer, told the Chicago Tribune.
Why lithium-ion batteries need extra scrutiny
What is it about lithium-ion batteries that makes them so explosive?
“We consumers do not want to lug around a huge battery. We want to slip our thin phone into our pocket or thin laptop into our bag. And that’s where lithium ion batteries come in — they pack a lot of energy into a small package. And when something goes wrong in that small package, that’s when you have big problems,” Drengenberg explains.
“With hoverboards, the battery is much bigger because you need enough energy to propel somebody down a sidewalk or up a hill and for numerous rides before it needs recharging. So now you’ve got more cells with a huge amount of energy. It’s also powering all the circuits that tell you when to stop or go or where you put your weight. Some even have LED headlights powered by those batteries,” Drengenberg says.
The UL mark on hoverboards
Certified hoverboards, if and when they're available, will have a holographic UL mark, Drengenberg says. While the holographic mark is used in special circumstances when there’s a risk of counterfeit marks being used. There are no UL-certified hoverboards on the market right now, Drengenberg notes.
(Photo: Courtesy of UL)
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