Electric Power Systems (EP Systems), the supplier of electric battery systems for major original equipment manufacturers (OEMs) including Boeing, Embraer and eVTOL developer Archer Aviation, is facing some headwinds on the certification program for its Electric Propulsion ion Core (EPiC) energy storage system.
The company had originally been aiming to get the Technical Standard Order (TSO) authorization for its EPiC energy storage system in Q2 of this year, but recently told eVTOL.com that the expected timeline has shifted to as late as next year.
Abbie Bean with EP Systems confirmed in an email that the company — like many others — has hit some snags.
“As is widely seen in the industry right now, supply chain constraints have caused disruptions and delays,” Bean said.
On top of that, “We are really moving on new ground with the [U.S. Federal Aviation Administration] to certify propulsion grade batteries,” Bean said, so delays are not uncommon for advanced air mobility companies developing aircraft components while working in new certification territory.
Bean noted that the FAA has stringent safety and containment requirements, including that “the energy storage system … be able to contain any failure [thermal runaway] without damaging the aircraft and allowing the aircraft to safely land.”
This is different than the requirements for a car battery, for example, because in that instance, if the batteries go into thermal runaway, “Automotive applications simply require the driver enough time to safely pull over and get out of the vehicle,” Bean said.
Another difference is that batteries for aircraft need to be designed in such a way to ensure they “meet the high safety standards without burdening the aircraft with weight.”
Getting a TSO authorization is an important early step in the certification process.
According to the FAA’s website, a TSO authorization is not an approval to install and use a material, part, or appliance in a civil aircraft; instead, it is a confirmation that the specified component meets the minimum performance standard.
“Receiving a TSO authorization is both design and production approval,” the website reads. “It means … the applicant is authorized to manufacture it.”
Delays to any of the individual components moving through the approval process could impact the eVTOL, eSTOL, and eCTOL developers relying on that piece to certify their aircraft — and many of those developers have aggressive timelines.
For instance, VoltAero’s service entry is targeted for 2024.
Earlier this year, the company announced that it had chosen EP Systems to supply its EPiC energy storage system for the Cassio 330 hybrid eCTOL aircraft, which VoltAero told eVTOL.com will have “near-STOL performance.”
VoltAero said the decision to go with EP Systems’ EPiC energy storage system was in part because it “was looking for developers who are already in the certification process with their batteries.”
Of course, the certification process is only one factor in the equation. Suppliers like EP Systems have to have their products meet their customers’ specific needs.
Since different aircraft have different operational and configuration needs, EP Systems developed its EPiC energy storage system with a modular, scalable design.
Bean said there are many benefits to modular building blocks, without sacrificing power or battery life.
“It is simply constructing the battery in a more flexible solution that can work across vehicle platforms and fit a spectrum of volumetric space requirements within different aircraft.”
Having modular aspects means airframers can “reduce the cost of development and certification for a custom battery system. They are able to take advantage of lower cost of development and then lower recurring cost once in production,” Bean said.
EP Systems’ chief technology officer Michael Armstrong previously told eVTOL.com that the EPiC module will be available in three variants: EPiC Power, EPiC Energy, and EPiC Ultra.
The EPiC Power system will be 180 watt-hour per kilogram (Wh/kg) with over 2,000 cycles at 80% depth of discharge (DoD), 30C discharge and 4C+ charge rates.
The EPiC Energy system will be 205 Wh/kg, also over 2,000 cycles at 80% DoD, 10C discharge and 4C charge rates.
Finally, the EPiC Ultra system will be 115 Wh/kg, with over 7,500 cycles at 80% DoD, 70C discharge and 40, 60, 80 amp hours (Ah) auxiliary power units (APU).
J. Scott Drennan, EP Systems’ board advisor, recently presented at the Transformative Vertical Flight symposium where he touched on the importance of looking at stored energy cost in terms of dollars per kilowatt hour per cycle.
Bean explained, “When considering a battery solution for the propulsion, an airframer needs to look at not just the upfront acquisition cost, but that cost in relation to the amount of energy and how long the battery will last (cycles). Many new advanced lithium chemistries may provide increased energy density, but they come at a higher cost with lower cycle life. EP Systems brings a strategic balance to optimize these factors and deliver a solution with today’s current lithium technology at the best dollar per kilowatt hour per cycle.”
Despite the recent delays it has been facing, EP Systems has certainly proven that it’s one of the companies to watch in the eVTOL battery space, as it continues to garner interest from OEMs. Besides VoltAreo, EP Systems’ current and publicly announced customers include the U.S. National Aeronautics and Space Administration (NASA), Boeing, Safran, Bell Textron, Embraer and Diamond.
Archer Aviation is also turning to EP Systems to supply its legacy VersaPower battery system for Archer’s Maker eVTOL demonstrator.