Chalmers researchers develop a cheaper, faster charger for electric cars

Researchers at Chalmers University of Technology have developed an integrated motor drive and battery charger that shortens the charging time for electric vehicles from eight to two hours, cutting the typical cost of charging from $2000 to "close to zero, ideally", said Saeid Haghbin, a postdoctoral research fellow at Chalmers.

Many governments are betting electric vehicles will play a key role in cutting transport carbon emissions. But until now, the batteries for electric cars models that have been brought to market remain expensive, short-lived and difficult to charge – key obstacles to widespread adoption. If the costs of making and running electric vehicles could be brought down, they may play a key role in cutting transport carbon emissions.

“Electric cars have been discussed as a possible solution to reduce carbon emissions for a long time, but scientists debate whether this mode of transportation is the future or not,” says Haghbin, who focused his doctoral work in electric power engineering on the optimal electric vehicle charger.  “If we manage to solve the main problems with the battery and the battery chargers, I think the electric vehicles will succeed. And in general, I think electric transportation will become more common in the future, for example trains, trams and plug-in hybrids,” he said.

Motor vehicles now account for one-fifth of all CO2 emissions in Europe and new more efficient models are needed if the EU is to fulfill its 2020 commitment to reduce greenhouse gas emissions.

Haghbin's innovation focuses on a new power transfer method involving what is known as a rotating transformer.  “The ideal scenario would be to have a charger powerful enough to charge a car in five to ten minutes, but this would cost over $100,000, which is more expensive than the car itself,” says Haghbin. “The question we posed was: how can we reduce the size, weight and price of the on-board charger?”

Since the electric motor and the inverter are not used during battery charging, the researchers looked into the possibility of using them in the charger circuit and building some kind of integrated motor and battery charger. In other words, would it be possible to use the motor and inverter in the charger circuit to increase the charging power at a lower cost?

“Instead of having a separate isolated battery charger, we introduced a new concept for the power transfer, the rotating transformer, which was developed to transfer electric power while rotating,” says Haghbin. “The battery is charged through the transformer and a split-phase electric motor that was especially designed for this purpose.”

Haghbin’s integrated charger has been patented and Chalmers is looking for a potential industrial partner for commercial development.  At the same time, Volvo AB is working on a concept for further enhancement to the system.

Model of the integrated motor drive and battery charger. This image shows a plug-in hybrid electric vehicle, which also has a fuel tank and a combustion engine, but the technology system works equally well with a purely electric vehicle.

The original article appeared on the Chalmers website.