Developers of new eVTOL aircraft insist their multirotor designs will be safer than any helicopter or airplane flying today, thanks to their highly redundant distributed electric propulsion systems. However, the lithium-ion battery technology that will power most of these aircraft has earned a bad reputation in recent years, with media outlets reporting instances of battery fires in electric cars, bikes, and scooters, as well as laptops and smartphones.
These fires are caused by a phenomenon called thermal runaway, in which a battery’s temperature skyrockets uncontrollably, leading to spontaneous combustion. Battery packs are typically designed with safeguards to prevent overheating and contain any unlikely fires that might erupt. However, thermal runaway events can still happen for a number of reasons, such as manufacturing defects, traumatic impacts, or increasing ambient temperatures. Although these occurrences are relatively rare, it’s a risk that electric aircraft developers cannot ignore.
Thankfully, researchers have recently come up with some innovative new methods to predict and prevent thermal runaway events before they happen, allowing battery manufacturers and aircraft developers to take a more proactive approach to dealing with the risk of battery fires. In a recent blog posted to Medium, a group of researchers and strategists with investment firm Mobility Impact Partners detail several promising new technologies that can help to “predict, detect, and proactively intervene, ensuring that thermal runaway never gains a foothold.”
The authors noted that “no single solution holds the magic bullet to this challenge,” although “a combination of diverse approaches and technologies is arising, each addressing different facets of this problem.” They provided four examples of companies taking innovative and proactive approaches to preventing thermal runaway.
Accure Battery Intelligence, a German company that specializes in data analytics and software for battery management, is using artificial intelligence to predict thermal runaway events days or even weeks before they occur, according to the MIP blog. Another company that uses this type of predictive analytics is Qnovo, a California-based start-up that uses computer models to identify batteries that are aging too quickly—a sign of defects or abnormalities that could lead to thermal runaway events.
Li-on Tamer, an Ohio-based company, offers a different approach to thermal runaway prevention. It has developed sensors that can detect off-gassing—a telltale sign of an impending thermal runaway event—five minutes before rapid self-heating begins. This could give pilots enough time to safely land and evacuate an aircraft before a catastrophic failure occurs.
In the event that an electric vehicle crashes, traumatic damage to the battery packs could result in a thermal runaway event. To prevent this from happening, Virginia-based Safire Technology Group has come up with a clever solution that uses a type of non-Newtonian fluid, or a liquid that solidifies when subjected to a force such as an impact. This non-Newtonian fluid “instantly transforms the battery from a liquid to a solid state, rendering batteries inert and preventing thermal runaways resulting from collisions,” the authors state.
While intervention strategies like those developed by Accure, Qnovo, Li-ion Tamer, and Safire can help to prevent catastrophic thermal runaway events, battery fires may not always be avoidable. In addition to new prevention strategies, the blog’s authors call for “better development and dissemination of suppression technologies and strategies to deal with the fires that will inevitably occur in spite of the best combination of all of the above.”