Their work, say the researchers, which includes testing of a prototype battery, reveals that eVTOL batteries have more stringent requirements than electric vehicle batteries in all aspects.
"I think flying cars have the potential to eliminate a lot of time and increase productivity and open the sky corridors to transportation," says Chao-Yang Wang, holder of the William E. Diefender Chair of Mechanical Engineering and director of the Electrochemical Engine Center, Penn State. "But electric vertical takeoff and landing vehicles are very challenging technology for the batteries."
"Batteries for flying cars need very high energy density so that you can stay in the air," says Wang. "And they also need very high power during take-off and landing. It requires a lot of power to go vertically up and down."
In addition, say the researchers, the batteries will also need to be rapidly recharged so that there could be high revenue during rush hours, with such vehicles having frequent take-offs and landings and recharging quickly and often.
"Commercially, I would expect these vehicles to make 15 trips, twice a day during rush hour to justify the cost of the vehicles," says Wang. "The first use will probably be from a city to an airport carrying three to four people about 50 miles."
Weight is also a consideration for these batteries as the vehicle will have to lift and land the batteries. Once the eVTOL takes off, on short trips the average speed would be 100 miles per hour and long trips would average 200 miles per hour, say the researchers.
The researchers experimentally tested two energy-dense lithium-ion batteries that can recharge with enough energy for a 50-mile eVTOL trip in five to ten minutes. These batteries, say the researchers, could sustain more than 2,000 fast-charges over their lifetime.
The researchers used technology that they have been working on for traditional electric vehicle batteries. The key, say the researchers, is to heat the