Compared to today’s electric vehicle chargers, the team’s new charger shortens the charging time from eight to two hours, and reduces the cost by around $2,000. These are huge improvements for what is a difficult problem.
Saeid Haghbin, doctor of electric power engineering at Chalmers, undertook his doctoral studies in order to develop the optimal electric vehicle charger. The result is a novel high-power integrated motor drive and battery charger for vehicle applications, where a new power transfer method has been introduced involving what is known as a “rotating transformer”.
Doctor Haghbin explains the goal, “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. 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 research team 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?
Doctor Haghbin explains the design with, “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. 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 on laboratory level. To achieve a more optimal system, further investigations and experimentation are necessary.
The product development and design has resulted in both a Swedish and an international patent. Chalmers is trying to find a potential industrial user, and Volvo AB is working on the concept for further enhancement to be used in its system. Things are progressing.
Doctor Haghbin has a practical viewpoint on the EV field saying, “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. 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.”
Doctor Haghbin has a firmly practical view that is intuitively correct. Cutting the cost of the charger dramatically and increasing its charge rate by four fold is going to have a major impact. Reducing the purchase price and solving the long wait times of today to get moving again is going to change the perspective of EVs and add many more potential buyers to the market.
Today one thinks ‘two hours of driving followed by eight hours of charging’, which for most everyone is a deal killer. But two hours of driving followed by two hours of charging is a very different circumstance. That isn’t including $2K freed up to buy more battery capacity, which might make it three hours of driving.
A four hour drive with a two hour charge followed by a four hour drive is a good day before an overnight charge. Its a long lunch break – but its would sell a lot better than today’s proposition and we’re almost there.
Thanks Doctor Haghbin!