Corporate Research & Development Center

It is a bother to plug and unplug the connector of a conventional wired charger for plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). To address this problem, Toshiba has developed an easy-to-use and safe contactless EV charger. The new contactless charger can transmit electric power over a distance of 17 cm, accommodating the requirement for high-bodied minivans. The charger has been tested in combination with a battery controller mounted on an electric vehicle. The test has verified that the charger has a capacity of 7 kW. Thus, it will halve the charging time, compared to 3-kW-class wired on-board chargers that are most widely used in Japan. The permissible right-left misalignment between the transmitting and receiving pads is up to 25 cm. This will ease the strain on drivers for parking accurately, compared to comparable chargers from other vendors that tolerate a misalignment of only up to 15 cm.

It has been pointed out that it is tedious to have to plug a cable of a PHEV or EV to a socket of a battery charger at the parking lots of homes and offices. Thus, in order to further expand the sales of PHEVs and EVs, there is a strong expectation for contactless charging using wireless power transmission that will ease the trouble of charging.

To address this need, Toshiba has developed a 7-kW contactless EV charger that employs a magnetic resonance method that provides a longer transmission range than the conventional electromagnetic induction method.
A combination test with an on-board battery controller has verified that the charger has a capacity of 7 kW. The transmitting pad measuring 60 × 40 cm placed on the ground can be up to 17 cm apart from the receiving pad of the same size mounted on the underside of an electric vehicle. This means the contactless charger can be used to charge the battery of minivans. The charger controls both the power transmitter and receiver via wireless LAN and dynamically chooses the optimal charging voltage according to the changes in the state of charge of the secondary battery, maintaining an almost constant power transmission efficiency. Consequently, the charger provides a high power transmission efficiency even when the transmitter and receiver coils are misaligned right-left by 25 cm.

We are planning to start a field test in 2014. Additionally, we will further increase the transmission power to expand the contactless charger applications to electric buses. We will also actively partake in international standardization and rulemaking efforts.