Charging Efficiencies: Wired vs Wireless EV Charging Systems
David Schatz, VP, Product Management, WiTricity
Plug-in charging is not 100% efficient. Energy loss, primarily in the form of heat, occurs every step of the way from the grid to the battery. Regardless of the brand, a plug-in EV charger is made of various components, any one of which may be more or less efficient than similar components in another charger.
The “efficiency” of the transfer of energy from the grid all the way to the battery encompasses a range. A traditional Level 2 home charger operates in the range of about 83-94% efficiency grid-to-battery depending on which one you buy. In the plug-in AC EV charging scenario, much of the heavy lifting is done on the vehicle through the On-Board Charger including the Rectifier PFC, Inverter, Transformer and Rectifier, which are needed to make the grid power into power that the EV battery can consume.
David Schatz leads product management for WiTricity, the leading provider of EV wireless charging technology. In this session, he will explain that with wireless charging, the vehicle does not need an “On-Board Charger,” reducing the charging complexity on the vehicle. The ground pad and vehicle pad convert the alternating current into the magnetic field that transfers power over the air gap. With the highly resonant design of the wireless charger, it is just as efficient as the isolation transformer used for plug-in charging. Wireless charging operates within an 88-93% band of efficiency, plus the added efficiency of not having to spend time plugging in and unplugging or the hassle of leaving your car.
David will provide graphical examples detailing where exactly the energy goes when charging an electric vehicle, and why wireless charging is just as efficient—and more convenient—than plugging in.
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