NO STRINGS ATTACHED

SWEDEN Park your car and the battery starts charging automatically. It may sound like a futuristic dream scenario for many electric car owners. However, the Neighbourhood Watch association in Stockholm’s Spånga-Tensta district has been charging cars without cables since May 2015.

When Börje Lindström reverses his Nissan Leaf from its parking space, some of the lights on the wall-mounted control panel linked to the induction charging plate on the ground go out to show that charging has stopped. The car belongs to a voluntary neighbourhood watch association in Spånga-Tensta, close to Stockholm, that Lindström is a member of. The Nissan Leaf is one of the most common electric cars in the market, but this one is different. Instead of conventional charging with a cable, it uses a wireless, inductive and automated charging solution.

The neighbourhood watch car covers about 120 miles (200 km) each week, usually during the daily rounds performed by the association’s members. Today, Lindström drives while Elvi Svensson sits beside him in the passenger seat. Lindström is happy with how the car runs and is charged.

“It can sometimes be a bit tricky to stop precisely over the charging plate,” he comments. Svensson adds: “But the control panel on the wall displays arrows for getting it right. The panel also shows when charging has begun and when the battery is fully charged.”

Börje Lindström and Elvi Svensson, Spånga-Tensta Neighbourhood Watch association.

Electromagnetic field
Johan Tollin, Head of the e-mobility programme at Vattenfall R&D, explains how the technology works:
“Inductive charging uses an electromagnetic field instead of a cable. The hard bit about this technology is to concentrate the magnetic field to where you want it. And high efficiency is obviously desirable.”

Lindström and the others in the neighbourhood watch association are part of a project named “Wich,” designed to test the wireless charging of electric cars for the first time in Europe. Twenty cars have been used to test a solution for wireless charging for over a year.

The cars – Nissan Leafs and Chevrolet Volts – have been specially adapted for this innovative technology: an A3 sized coil has been fitted under the boot.

“In order to charge the car, we have a box placed on the ground or on the garage floor that contains the primary coil which in turn communicates with the secondary coil in the car. The charger is powered from a normal 230 V power socket,” says Tollin, also commenting that the charging plate works even if it is covered with snow or dirt.

“A further advantage of inductive charging is that the charging plate can be cast in asphalt or concrete.”

According to Tollin, Vattenfall is taking part in this project for reasons other than to promote the development of this technology.

“Wireless charging technology is interesting in itself, but it’s actually the possibility of automatic charging, offered by this technology that will be particularly beneficial for the development and proliferation of electric vehicles,” Tollin says. “Park and go, that’s what automatic charging is all about. The driver does not have to do anything like connecting through a cable.”

At the same time, Tollin does not want to condemn cables.

“We will live with them and they will still be around and indeed dominate for a long time to come. I see automatic charging mostly as a future option for these cars.”

Automatic charging
Surveys of the users of electric cars in this project show that many of them have experienced problems in getting the charging to work due to the difficulties of parking the car precisely over the charging plate. Per Wahl, responsible for the cars used by Spånga-Tensta Neighbourhood Watch, shares this view.
“It can be a bit tricky, especially if you have a narrow parking space. Before we started with this, I thought it was just a small detail to remember to connect a charging cable, no big deal. But now I’m totally for induction charging. On a cold day with a dirty car and cable, it’s an ideal solution. You merely have to park and charging starts automatically.”

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