Driving forward with automatic EV charging

In order for EVs to continue to grow in popularity, more charging stations must be integrated into infrastructure. However, with the number of EVs on UK roads now over 0.5m, having more charging stations required could become a problem.

Charging challenges

Charging stations in city centres can be an eyesore, and bulky cables and plugs can cause inconvenience in people’s garages. In fact, a study published in Nature earlier this year found dissatisfaction with the convenience of charging to be a key reason for drivers to discontinue with an EV and switch back to an internal combustion engine.

Contactless inductive charging offers one solution to the typical visual and mechanical annoyances of charging. The wireless charging technique involves a transmitter coil embedded in the garage floor or road surface, and a receiver coil in the bottom of the vehicle. Electricity from the grid runs through the transmitter coil, which generates a magnetic field. The magnetic field then induces current in the receiving coil, thus charging the vehicle’s battery.

However, even contactless charging comes with disadvantages. In order to embed the coils in the floor, the ground has to be opened up and then refinished, causing inconvenience and visual defects. In addition, without a wire to transfer the power, the maximum output is currently around 3kW in most cases, resulting in long charging times. Furthermore, a significant portion of the power is lost during charging compared to plug-in cables, and this is magnified if the car is not parked precisely over the coil.

An automated solution

Fortunately, it is possible to avoid both the annoyance of long cables and the inefficiency of contactless charging. Instead, a small, sleek and flat charging structure can be fixed onto the floor. The structure can be as little as 6cm high, providing an inconspicuous solution.

Similar to contactless charging, the vehicle must be parked over the charging structure, but its position doesn’t need to be as exact. This is because a retractable, automated arm then extends out of the structure with a connector placed at the end, which seeks its counterpart on the car’s underbody.

The two components seek and connect by exchanging information via encrypted wireless communication. An ultrasonic system ensures the arm accurately finds its target. Within less than 15 seconds, the connection is established.

The connector is a conical-round current carrier, and can therefore make full contact even if the car is not parked in the optimal position. As long as the connector is within a range of 50cm², the car can be parked at any angle and still get connected. The technology can handle up to 100kW DC, making charging time just one hour.

Perfecting the system

The system uses motors from the FAULHABER CR series, which has graphite commutation, a very robust type of commutation suited to high power applications. The motors also feature powerful neodymium magnets and a high copper content rotor, delivering supreme power.

EMS is the sole UK supplier of FAULHABER motors, and also has a selection of complementary planetary gearheads available. Adding a planetary gearhead reduces the motor speed and increases the torque, making the motor run at a higher and more efficient revolutions rpm.

The electric car market is growing rapidly, but charging difficulties are limiting its potential. Automated charging techniques avoid the inconvenience of bulky cables in typical plug in methods and the inefficiency of contactless charging, therefore helping to accelerate EV adoption.