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A cheaper and faster way to charge electric vehicles

30 April 2013

Researchers have developed an inexpensive integrated motor drive and battery charger for electric vehicles that can charge in just two hours.

Concept of the integrated motor drive and battery charger. The 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 work, carried out by Dr Saeid Haghbin at Chalmers University of Technology in Sweden, has resulted in a novel high-power integrated motor drive and battery charger for vehicle applications that involves a new power transfer method based on a 'rotating transformer'. The cost of the system is estimated at around $2,000.

“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 Saeid 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 Saeid Haghbin. “The battery is charged through the transformer and a split-phase electric motor that was especially designed for this purpose.”

The Chalmers integrated charger is, from a university perspective, still at the laboratory stage. To achieve a more optimally performing system, further investigations and experimentation are necessary, but the idea has received a Swedish and an international patent. Chalmers is currently seeking a potential industrial partner, while Volvo AB is working on the concept for further enhancement to be used in its own system.




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