Wired has a good article on fires from “hoverboards,” which are essentially very small hands-free electric scooters. Here is an example. Start at about the :30 mark to see how these devices explode, and can easily set a house on fire.
Neither Wired nor other news stories have much constructive advice about how to reduce the chance of fires. As they point out, buying a well-made model is important, but at present there is no way to distinguish the well-made ones from the knock-offs. And most are cheap knock-offs by companies that will be gone in a year.
I have some experience with the underlying cause of these fires, their Lithium-based batteries, because I use them in radio controlled aircraft. Fires of these batteries are not common, but they happen. Two people in San Diego who I know directly have had major fires. One lost a 2-unit condo, the other a detached workshop. The second one happened to an expert in RC flying!
Here’s the cause: Any lithium-polymer battery that is overcharged, or has a short circuit, will catch on fire. The batteries in our cellphones and computers are very safe because the manufacturers realize this, and provide several levels of protection. Both the battery itself, and the charging circuit, monitor to prevent overcharging. And the battery is designed and manufactured to a high standard of safety. (You could still cause a fire by driving a nail through the battery, or a violent accident, but that is about all.)
In Radio Control flying, we mainly use cheap batteries to save weight. But we use expensive chargers to prevent overcharging, and we follow these rules:
- Never leave a battery alone while it is charging.
- Expect to spend $50 to $100 on a good name-brand charger. Learn to use it properly; they require simple programming for each type of battery.
- Charge on a concrete surface, outside, or in a fire-safe bag. In my case, since I live in a warm climate, I can use all 3.
- Keep a fire extinguisher or a bag/bucket of sand handy. The smoke from even a small fire smells awful, and will stink up a house.
- If the battery begins to swell, treat it as suspicious. If it swells a lot, dispose of it. (Disposal is its own procedure.)
- After any crash, treat the battery as suspect, especially for the first few hours.
I suspect that what has happened to hoverboards is that the makers use cheap chargers that do not protect well against overcharging. The batteries themselves don’t have proper built-in protection circuits. (If you look at a removable notebook or phone battery, the packaging conceals a fair amount of circuitry.) “Many modern batteries incorporate all kinds of safety measures, such as emergency vents, and many products filled with lithium ion batteries have to endure a barrage of drop tests, crush tests and electrical stress tests before they can pass.”
Despite these precautions, battery fires happen. We try to ensure that when they happen, they don’t have serious consequences. I was lucky because early in my RC flying I had a battery start to smoke while being charged. After that, I took the problem seriously. This picture is not mine!
Where did you get the picture? My company, ESSPI (Energy Storage safety Products International) is in the process of consulting the National Fire Protection Association on the Li ion battery fire safety issue.
Thanks for the question, and I wish you luck with your project. The need will only increase.
I got the image from RCgroups.com, a web site for RC hobbyists. It has a variety of threads on safety of Lipo batteries, and some of them include pictures and stories of accidents. Original picture: http://www.rcgroups.com/forums/showthread.php?t=1202291
Long thread called “Lipo Fires are Real!” is worth looking at. http://www.rcgroups.com/forums/showthread.php?t=719116
Thanks for keeping the battery fire topic in view. I am a big fan of li technology. Much like any energy storage medium, it has a downside. No worse than internal combustion engines, maybe safer! However, industry should not ignore the risk issues. We are currently in the process of developing hover board charging stations for universities and other public spaces…fire suppressed and contained. There is a company in Michigan that is developing an RC charging box that fits the bill mentioned above. It is quite affordable too from what I hear.
Federal Aviation Administration and other regulators still working on reducing risk of aircraft fires. A new rule: batteries must be mostly discharged when they are shipped by air. “… Freighters would still be allowed to carry both types of batteries, but with the 30% charge limit for lithium-ion batteries, down from the typical 50%. FAA testing has shown the potential for thermal runaway decreases with the state of charge.”