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How Far, How Long, Will Your Batteries Let Your eVTOL Fly?

In aviation, time is money. This is also true in UAM.

Entrance of Stanford University.
Faculty and students at Stanford University are contemplating the optimal battery life for eVTOLs. (Image courtesy of Stanford University.)

They say time is money. Perhaps nowhere is the consumer-operator more conscious of time than in aviation.

Travelers worry if their flight is on-time. If departure is delayed, they worry they’ll be able to connect from one flight to another. Flight operators fret over aircraft availability, regulations dictating crew time for safe operations, and myriad other factors that can impact operations, reputations, and bottom lines.

When flight ops depend exclusively on battery power, certain questions loom large in the minds of eVTOL developers and operator hopefuls. Those questions include: How long will lithium-ion batteries last; how often will an operator need to charge them; and how much time is needed to maintain the batteries or swap them out for fresh ones.

Battery Use in Regional and Urban Air Mobility Settings

These were the questions two researchers at Stanford University sought to answer in their study,  Forecasting the Operational Lifetime of Electric Aircraft Through Battery Degradation Modeling. Dr. Juan J. Alonso, a professor in Stanford’s Department of Aeronautics and Astronautics, and the founder and director of the Aerospace Design Laboratory (ADL), along with his protégé, Matthew A. Clarke, a Ph.D. candidate at Stanford, the pair presented their findings at the AIAA SCITECH 2022 Forum.

Alonso and Clarke’s assessment attempted to accurately account for how the repeated use of the batteries might reduce efficiency in time-dependent factors. They modeled flight ops in regional and urban air mobility settings and predicted that, after a year of continuous operations, such heavy frequency can reduce battery capacities by as much as 45 percent.

The findings suggest that lithium-ion battery developers consider designing and engineering battery cells specifically for aerospace use. For example, batteries with a high C-rate discharge at the beginning and end of the battery’s life cycle, a process known as battery inverse-design.

The study’s finding also suggest development of more vigorous thermal management system algorithms based on the predictability of thermal loads.

Perhaps of greatest interest to eVTOL developers and operators is the prospect of creating flight operation strategies that optimize an eVTOL’s life before substantial ground maintenance is required.

All that valuable information suggests a second aphorism: Forewarned is forearmed. eVTOL operators, lithium-ion battery developers, start your engines, and prepare for takeoff.

Dave Clarke

Dave Clarke is a California-based writer who is fascinated by the way technology changes our lives.