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2014-02-24

Toyota pulls plug on plug-in EV charging


Toyota is developing a wireless EV charging system based on magnetic resonance

Toyota is developing a wireless EV charging system based on magnetic resonance Recharging a plug-in hybrid or all-electric vehicle could in future be as simple as parking the car. Toyota has announced verification testing is to begin later this month of a new wireless battery charging system it has developed for vehicles that use an electric power-train. The new technology allows a vehicle to be charged simply by parking it in alignment with a coil set into the surface of the ground. This makes the process simpler and easier, dispensing with cables and connectors. The Toyota charging system transmits electricity using magnetic resonance created by changes in magnetic field intensity between a transmitting coil in the ground and a receiving coil in the car. It is designed so that it can reduce any loss in power transmission efficiency caused by misalignment or height differences between the coils. Initial specifications for the magnetic resonance system include a working frequency of 85kHz and an input voltage of 200V AC. The present system only has a charging power of 2kW, less even than the 3kW 'slow' charge points used predominantly for overnight charging. However, given that the Prius plug-in hybrid has a relatively small battery, the system can full charge the battery in around 90 minutes. The system is being developed with a future market launch in mind. Measures have been taken to minimise any electromagnetic interference with nearby equipment, and the transmitting coil in the ground has been made robust enough to withstand vehicles driving over it. To help the driver align the car correctly, Toyota has developed a function for its Intelligent Parking Assist system that shows the position of the transmitting coil in a parking space. The test programme involves three plug-in hybrid used by homes in Aichi prefecture in Japan. It will assess user satisfaction, the system’s ease of use, misalignment rates and charging behaviour, such as how often charging takes place and timer-based charging it used. Toyota will use the test results to develop the technology further, with the ultimate aim of bringing the system to market – potentially at higher charging rates. Toyota believes its commercialisation will help promote the use of electrified vehicles and mobility options that are smarter, easier to use and kinder to the environment