Marc Rosenmayr, CEO of electronics for Hella (hellausa.com) in North and South America, envisions a future in which his electric vehicle recharges wirelessly in a parking space while he buys a cup of coffee.
“With wireless charging pads installed in the parking lots of businesses, you could charge for 10 minutes while grabbing a coffee, and another 10 minutes when you stop at the drug store,” Rosenmayr says.
And he isn’t simply imagining this technology in abstract: Hella and Vahle (vahleinc.com)—maker of industrial wireless energy transfer systems—have developed a wireless, inductive EV charging system.
The system consists of two stationary components and a coil placed on the bottom of the vehicle. The main stationary component is the battery charging system, which contains the inverter and connects to the power supply network. The second component is the charging pad itself, and receives alternating current from the battery charging system. The power supply is the same as existing, cord-dependent 220-volt charging units. The pad sits on the floor of parking garages or embeds into the ground outside. When a vehicle parks above the pad, magnetic coupling occurs between the coil on the bottom of the vehicle and the pad, charging the battery.
“The field is stronger the closer you are to the mat—it’s most efficient if the gap is smaller,” Rosenmayr says. The preferred distance between the vehicle coil and the mat is four to eight inches.
A shield protects the interior of the vehicle from the magnetic field. A “foreign object detection” system made up of sensors in the stationary charging pad cuts off the energy transfer if a metal object (other than the car’s charging coil) is detected, preventing potential fire hazards.
Another benefit is extended battery life. “Battery systems are less susceptive to aging if you do smaller, more frequent charges than big ones,” he says. “Batteries are all about chemistry. You move a lot of chemistry from one stage to another during a long charge. If you do small charges, you only use a part of the battery.”
Thinking further into the future, Rosenmayr says wireless charging could allow for charging at stoplights, and possibly along entire stretches of highway provided the infrastructure was there to support it.
Despite these far-out possibilities, the next step is developing standards for wireless charging to ensure the stations are compatible between various EVs, as well as different charging station designs.
“We are working together with SAE to establish universal standards to ensure that all systems, both stationary and onboard vehicles, are able to communicate and work together,” Rosenmayr says.—ZP