Energy management using a quick charger with storage battery for electric vehicles

We developed and field-tested an electric vehicle quick charger (EVQC) with storage battery to suppress the lengthening of charging time while preventing a rise in a building's peak power usage caused by EV charging. This EVQC features a demand control technique that determines the amount of power to be used by the charger according to the amount of power used by the building. In addition, charging the storage battery of this EVQC with surplus power from a photovoltaic power generator installed on the roof of the building prevents the flow of power back to the utility grid. In this paper, we describe this demand control technique and report on the results obtained by a field test. We also propose a new battery-capacity estimation method using storage-battery charging/discharging data and show that the method can make estimations with good accuracy at an error rate of approximately 3%.