The list of suppliers for the Bell Nexus air taxi includes some of the biggest names in aerospace. There’s Safran, a leading turbine engine manufacturer, which is collaborating with Bell on the aircraft’s hybrid-electric propulsion system. Thales, which is developing fly-by-wire flight controls for the Nexus as it has for Gulfstream jets. Actuator systems provider Moog, which has products on platforms ranging from the Boeing 737 to the Lockheed Martin F-35. And Garmin, the avionics supplier with such extensive civil market penetration that it hardly needs an introduction.
Then there’s Electric Power Systems (EPS), which is providing the Nexus’s energy storage system and battery management technology. A relatively young company with fewer than 100 employees in Logan, Utah, EPS would seem to be in a different league than, say, Thales, which employs 80,000. Yet according to Bell VP of Innovation Scott Drennan, the lithium-ion battery developer has more than earned its place on the list.
“[EPS] is fantastic,” Drennan told eVTOL.com. “[It’s] this wonderful startup that combines the best of that startup mentality of going fast, serving their customer, finding new solutions . . . and a deep understanding of the aerospace requirements for safety and lightweight integration into the vehicle. So our two teams just have an incredible relationship.”
Bell isn’t the only legacy aerospace company paying attention to EPS. In September, EPS announced that Boeing HorizonX and Safran Ventures had jointly invested in the company during its Series A funding round, providing much-needed capital as the company seeks to develop “a highly automated industrial base capable of producing aviation-grade energy storage systems at an unprecedented scale,” as EPS put it.
The company has big ambitions — and if the electrification of aircraft continues, it could grow to become a dominant player in hybrid and fully electric propulsion. Indeed, said CEO Nathan Millecam, “our aspirations are to become a household name in aerospace and to really be the company that powers this electric renaissance that we see happening right before our eyes.”
Aviation standards, automotive scale
If you’ve never heard of Logan, Utah, you’re not the only one. A 90-minute drive north of Salt Lake City, this town of 50,000 isn’t necessarily the first place you’d expect to find a cutting-edge technology startup. However, a combination of factors enticed EPS to relocate here from the Los Angeles area in 2017, including the strong local talent pool at Utah State University, enthusiastic support from city and state governments, and Utah’s appealing outdoor lifestyle and low cost of living.
When eVTOL.com visited EPS in Logan earlier this year, the company was still scattered across a handful of rented office spaces. However, it was at work on a new facility that will consolidate its operations, including manufacturing and advanced R&D work. This brand-new facility is expected to be completed in January 2020, and will include roughly 70,000 square feet worth of manufacturing space by the end of next year.
“Part of what [we’re doing] is building what we call a life lab,” Millecam explained. “The life lab allows us to rapidly simulate field performance results on advanced concepts . . . to know what type of performance and what type of direct operating costs we’ll get out of that vehicle.” That capability will be particularly valuable for the eVTOL industry, where low operating costs will be key to success.
EPS traces its roots to a research group that originally formed within the avionics systems company Phillips Aerospace starting in 2007, then migrated through multiple companies before finding its way back to Phillips in 2016. Millecam, who had previously worked for Honeywell and in the semiconductor industry, spun off EPS as an independent company along with co-founder Randy Dunn the same year.
Before that, the group was primarily focused on battery technology for automotive applications, not aviation. “When I hooked up with the team, I saw the value that it could provide to aerospace,” Millecam recalled. “It had all this great integration capability, it was highly modular, and because the team came from a [military aerospace] background, they developed [their products] to the standards that they were used to, yet they did this at a cost point both on the development side and the recurring side that was very competitive.”
With the growing interest in urban air mobility, EPS’s founders decided to leverage their combination of automotive and aviation expertise to work toward “high-volume production, where traditional legacy aerospace did very small volumes and didn’t really support the needs of the marketplace,” he said.
According to Millecam, the company’s products constitute complete energy storage systems, not just battery cell technology. Indeed, because the latter is evolving constantly, EPS can adapt its systems to whatever current cell technology makes sense.
“The reason why we call it an energy storage system is because there’s a lot of key technologies that are needed to put around a cell to really make the lithium-ion cell work in an airborne application,” he explained. “Those are things [such as] software, controls, power electronics, which ultimately get translated into a power distribution system, as well as a thermal management system that can handle both thermal normal and thermal runaway conditions.”
Millecam said that EPS is working to develop a “library” of product offerings in order to provide customers with efficient yet flexible solutions.
“If a customer [comes in] with unique energy storage system requirements, we can pull from the library and configure it in a way that gives them a unique system, but then the background modules have a lot of flight heritage to them with associated airworthiness documentation,” he said.
Technology for the entire industry
Beyond the Bell Nexus, EPS has revealed its involvement with two electric airplanes — the Bye Aerospace eFlyer and Embraer’s Ipanema demonstrator. The company has a number of other aerospace customers, Millecam said, but most of these are still confidential.
EPS has also had high-profile involvement with NASA’s X-57 Maxwell demonstrator. NASA selected the startup to build a lithium-ion battery pack for its electric X-plane because some of the major government contractors found the demanding specifications “impractical,” according to X-57 principal investigator Sean Clarke. In a recent article on NASA’s website, Clarke said the agency favored EPS’s “aggressive” approach: “We’re an aggressive project, and we’re willing to accept a degree of risk going in, and it’s paid off.”
But it didn’t pay off right away. EPS’s initial battery design succumbed to thermal runaway during testing, with an intentional simulated short-circuit in one cell causing the entire battery pack to burst into flames. As Millecam recalled, “We were trying to be very aggressive on weight — that was required in order to hit the range target of the vehicle.” After the first pass design failed in testing, he said, “we basically had to completely rethink our containment strategy on the pass two design.”
That second design proved to be a success, able to stop thermal runaway at an individual cell level. And EPS gained valuable insights in the process of creating it. “We were also able to develop some simulation tools that were pretty groundbreaking to help us rapidly prototype and test different materials, different combinations of materials, different thermal management strategies, to really optimize the packaging and to get the weight out, but still achieving that very high safety standard,” Millecam told eVTOL.com.
Now, he said, “We’re probably about two generations beyond the X-57 design and we’ve been able to optimize our packaging overhead significantly. Even though X-57 was groundbreaking in its weight, we’re doing a lot better than we were back then.”
Bell’s Scott Drennan teased further innovations made by EPS on the Nexus project, including additional weight reductions, new approaches to the integration of battery management systems, and the “smoother, cleaner integration of the aircraft electrical requirements,” he said. “I will eventually historically list out all of the mutual innovations that we’ve made together as we started to apply their baseline technology into our system — and it’s all just on that startup mentality that they have.”
Drennan expressed enthusiasm for the funding that EPS has received from Boeing HorizonX and Safran Ventures, as well as the fact that neither investor is seeking exclusive access to the startup’s technology. That was an important consideration for EPS, Millecam told eVTOL.com.
“HorizonX and Safran Ventures have been fantastic investment partners to work with. These entities share our common view to advance the technology and build out a manufacturing base to benefit the entire industry,” he said.
Editor’s note: For a more in-depth discussion on battery development and certification, find our Q-and-A with Nathan Millecam here.