Electric vehicles (EVs) will meet the daily travel needs of drivers longer than commonly assumed, according to the first study of its kind carried out by scientists at the US Department of Energy's Lawrence Berkeley National Laboratory. Many drivers and much prior literature on the retirement of EV batteries have assumed that EV batteries will be retired after the battery has lost 20 percent of its energy storage or power delivery capability. This study shows that the daily travel needs of drivers continue to be met well beyond these levels of battery degradation.
Electric vehicles (EVs) will meet the daily travel needs of drivers longer than commonly assumed, according to the first study of its kind carried out by scientists at the US Department of Energy's Lawrence Berkeley National Laboratory.
Many drivers and much prior literature on the retirement of EV batteries have assumed that EV batteries will be retired after the battery has lost 20 percent of its energy storage or power delivery capability. This study shows that the daily travel needs of drivers continue to be met well beyond these levels of battery degradation.
Samveg Saxena, who leads a vehicle powertrain research program at Berkeley Lab, analyzed real-world driving patterns and found that batteries that have lost 20 percent of their originally rated energy storage capacity can still meet the daily travel needs of more than 85 percent of U.S. drivers.
He and his research team also analyzed battery power fade and found that even after substantial loss in battery power capabilities performance requirements are still met.
"There are two main reasons people are hesitant to buy an EV: first, they're unsure it will satisfy their mobility needs, and second, they're afraid the battery won't last the whole life of the car and they'll have to replace it for a lot of money," said Saxena, who has a PhD in mechanical engineering.
"We show that, even after substantial battery degradation, the daily travel needs of most people are still going to be met."
The analysis of battery life was published online recently with open access in the Journal of Power Sources, "Quantifying EV battery end-of-life through analysis of travel needs with vehicle powertrain models," which Saxena co-authored with Jason MacDonald of Berkeley Lab and Caroline Le Floch and Scott Moura of UC Berkeley.
With today's EV batteries, "end of life" is commonly defined as when the storage capacity drops down to 70 to 80 percent of the original capacity. As capacity fades, the vehicle's range decreases. The Berkeley Lab researchers decided to investigate the extent to which vehicles still meet the needs of drivers beyond this common battery retirement threshold.
To conduct the study, the researchers took nearly 160,000 actual driving itineraries from the National Household Travel Survey conducted by the Department of Transportation. These are 24-hour travel itineraries showing when a car was parked or driving, including both weekend and weekday usage by drivers across the United States.
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Electric vehicles image via Shutterstock.
