78
find a power station, grab the plug, and stick it in their
EV’s socket as if pumping gas.
With conductive charging, the driver doesn’t techni-
cally have to be involved. Demonstration projects exist
with robotic arms that can automatically insert the plug
into the EV, such as the Tesla charging snake that was
revealed back in 2015 (but has yet to be implemented
at any of Tesla’s public Supercharger stations). Though
this eliminates driver involvement, it can’t help but feel
clunky. It’s like replacing your remote control with a
robot that physically presses the buttons on your TV.
Stockinger wanted to come up with a way to charge
EVs that retained the efficiency of conductive charg-
ing without sacrificing the easy automation of wireless
charging. He came up with a solution called Matrix
Charging, and he founded Easelink to develop and com-
mercialize the technology.
Matrix Charging
There are two components to Matrix Charging: the
Matrix Charging Pad, a slim rectangular prism dotted
with an array of metal contact points, and the Matrix
Charging Connector, an extending rubber tube that’s
positioned on the underside of an EV.
The Matrix Charging Pad is installed on the surface
of a parking space. It’s connected to a power source, and
when an EV with a Matrix Charging Connector parks
over the Pad, the Connector automatically extends
down until it makes contact with the Pad. The Connec-
tor magnetically aligns to the closest contacts on the Pad
and commences charging. Even though there are hun-
dreds of contact points on the Pad, only those contained
within the Connector tube are activated. The rest of the
Pad remains electrically neutral.
The first and current generation of Matrix Charg-
ing provides AC charging with up to 22 kW of power.
Transfer efficiency is over 99 percent, the same as for a
plug-and-socket connection. Easelink is developing a
second generation of Matrix Charging that will pro-
vide 22 kW AC charging and 50 kW DC charging. The
company also has plans for a third generation that will
provide more than 100 kW of power.
Easelink considered various design options when
developing Matrix Charging. The first big question was
whether to use conductive or inductive charging. Hav-
ing found a solution that could readily be automated,
Easelink chose conductive charging for its low cost and
high power transfer.
The second question was where to place the charger.
Should it be above the vehicle, under the vehicle, or off
to the side? Easelink chose to put the Matrix Charging
Pad under the vehicle.
“The only two parallel surfaces that are always avail-
able are under the vehicle. That’s the underbody of
the vehicle and the parking ground itself,” Easelink’s
Sebastian Demuth told Charged. “You don’t need a wall
to mount a wall port, you don’t need a pole to mount
the charging device, so the ground is the easiest way to
integrate such a technology.”
The third design dilemma was the choice of where to
put the charger’s moving parts. Easelink decided to keep
the moving parts of the Matrix Charging Connector
on the EV itself, keeping the Charging Pads static and
resilient. Even so, the vertical movement of the Connec-
tor’s rubber tube is delivered through a single actuator,
keeping the number of moving parts to a minimum.
Finally, Easelink needed to determine the nature of
the conductive contact. Should there be a socket in the
ground and a plug extending from the EV, or vice versa?
Easelink went with neither option, instead opting for a
planar geometry for the contact surface.
“It has to be a planar surface,” Demuth said. “That’s
easiest to clean. It’s traversable, and has no obstacles. So
it’s barrier-free, and can be integrated seamlessly into
the ground. And that’s how the product was designed.”THE INFRASTRUCTURE
The Connector magnetically
aligns to the closest contacts
on the Pad and commences
charging. Even though there
are hundreds of contact
points on the Pad, only
those contained within the
Connector tube are activated.