AI & Autonomy, Air Taxi

Challenges, considerations and issues for tomorrow’s “flying cars”

By Mark Robins | December 22, 2023
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This is the third in a series of articles exploring development of eVTOL batteries. 

To fulfill the emerging need for new aerial vehicles designed for urban air mobility, electric vertical take-off and landing (eVTOL) aircraft cannot be ignored. Different from conventional avionic components in many ways, eVTOL battery performance and safety requirements especially need to be considered and examined.

While avionics batteries are used primarily for backup systems and have a comparatively low rate of charge and steady predictable discharge, Manuel Terranova, CEO and president of Peaxy, San Jose, Calif., says eVTOL batteries need to support both high Crates during takeoff and maneuvering, combined with low C-rates during cruising. “Peak power performance needs are much more significant with requirements for operating at 10- 20 C rates. As a result, they have a higher energy density than conventional batteries. eVTOL batteries are also designed for increased thermal stability and to allow for more flexible deployments, with features such as enhanced modularity to suit different types of aircraft and trip distances.”

Battery technology impacts eVTOL development; it affects the range, carrying capacity, charging time, and maintenance costs. An aircraft’s different power requirements in each flight phase are more evident in the eVTOL. A typical eVTOL trip has five stages: takeoff, climb, cruise, descent, and landing, where the power output required by the battery at distinct states of the vehicle’s flight is different. Most eVTOLs use the most power while taking off and landing.

“Compared to many other electric mobility applications, eVTOL batteries typically require a higher level of performance, such as having higher specific energy and power, and the ability to work continuously at a high discharge rate while still having a suitable life span,” says Dr. Ionel Stefan, chief technology officer at Amprius Technologies Inc., Fremont, California. “Plus, in the quest to optimize eVTOL operational efficiency, minimizing charging times assumes paramount importance, particularly during peak demand periods. Conventional avionic batteries are used as backup power for auxiliary systems, while eVTOL batteries are the main energy source. As such, they are of much larger capacity and energy density is a critical metric directly linked to the weight of the battery.”

San Leandro, California-based Cuberg’s batteries enable eVTOLs to take off, coast and land. Cuberg technology uses a lithium metal anode and a proprietary liquid electrolyte to simultaneously solve the interlocking challenges of battery performance and manufacturability. “While incumbent battery technologies, such as lithium-ion, can be too heavy and low-performing to enable the business case for eVTOLs, Cuberg’s battery cells are lightweight and high-performance,” says Richard Wang, founder and CEO of Cuberg. “Our high energy-dense lithium metal cell provides more specific energy and power. Researchers have understood the potential of lithium metal anodes for many years, but we are making unique strides in actually commercializing this technology. Our proprietary liquid electrolyte stabilizes high-energy anode and enable long cycle life. This is key, in particular, to meet safety requirements for aviation.”

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