Researchers move closer to charging an EV as fast as filling a tank of gas
Swiss researchers, however, say that by increasing the electrical charge, EVs can potentially be fully charged in about 15 minutes.
In a paper published today, researchers from the Ecole Polytechnique Federale de Lausanne (EFPL) (Swiss Federal Institute of Technology in Lausanne) said an EV charging station with 4.5 megawatts (MV) of power could charge a vehicle in 15 minutes.
Unfortunately, 4.5MW is the power equivalent of 4,500 washing machines. "This would bring down the power grid," the researchers stated.
To overcome drawing such a significant charge from the power grid at one time, the researchers created a buffer storage system that disconnects from the grid before releasing the 4.5MW charge to an EV.
"We came up with a system of intermediate storage," said Alfred Rufer, a researcher in EPFL's Industrial Electronics Lab. "And this can be done using the low-voltage grid (used for residential electricity needs) or the medium-voltage grid (used for regional power distribution), which significantly reduces the required investment."
The EPFL researchers, along with other partner universities, built an intermediate storage battery. In the space of 15 minutes, it provided the 20 kilowatt hour (kWh) to 30 kWh needed to charge a standard electric car battery.
The "Intermediate" storage is achieved using a lithium iron battery the size of a shipping container, which is constantly charging at a low level of power from the grid. When a car needs a quick charge, the buffer battery promptly transfers the stored electricity to the vehicle.
"Our aim was to get under the psychological threshold of a half hour," Massimiliano Capezzali, deputy director of the EPFL Energy Center and leader of the research project, said in a statement. "But there is room for improvement."
Last year, Tesla opened up to the rest of the auto industry its patented designs for Supercharger stations, a quick charging technology that Tesla claimed is the fastest EV charger on the market.
Supercharger stations are able to partially charge a Tesla Model S sedan in 30 minutes, giving it a 170-mile range. A full charge takes 75 minutes.
Superchargers consist of multiple Model S chargers working in parallel to deliver up to 120 kW of direct current (DC) power directly to the battery, according to Tesla.
Tesla currently has 591 Supercharger stations with 3,425 Superchargers around the world. Last year, the company released an over-the-air software upgrade for its cars that tracks charging station locations and alerts drivers when they're out of range of those stations.
As part of the EPFL Industrial Electronics Lab's quick charging project, researchers built gas station prototypes to determine how they'd need to be modified as gas-powered cars slowly die out and are replaced by EVs.
The research showed that a quick charging station able to handle 200 cars per day would need intermediate storage capacity of 2.2 MWh, which require an Intermediate battery system the size of four shipping containers.
"Electric cars will change our habits. It's clear that, in the future, several types of charging systems -- such as slow charging at home and ultra-fast charging for long-distance travel -- will co-exist," Capezzali said.