Ben Goren via EV wrote:
brucedp5 wrote:
In Tesla’s defense, Straubel says that the current 120-kW Supercharger
“seemed pretty crazy even 10 years ago” when conventional chargers delivered
under 10kW. So, maybe this theoretical 720 kW Supercharger is possible…in
time.
But what’s the work-around solution for the size and heft of the cable? We
don’t see one. Do you?
That's actually fairly straightforward. When I worked at Schott Power
Systems, we built a 100kw version of the GM Magnecharger. 100kw isn't as
bad as you might think; 330v at 330a for example. We could have used 1/0
welding cable, for example. It would still be smaller than a gas pump
hose. 1/0 is rated for 125 amps continuous, or 375a for 10 minutes. 10
minutes at 330a is 55 amphours, or 16 KWH; not bad for a quick boost.
But we chose to use a liquid-cooled cable. The charging cable was a
hose, with two smaller wires and another hose inside. Oil was pumped out
the inner hose, and back around the wires and outer hose. The liquic
cooling was necessary for the paddle transformer on the other end
anyway, as at 100kw it also generated a significant amount of heat that
needed to be removed.
The same scheme could be done at 720kw. The wire can be arbitrarily
small as long as you have sufficient cooling. You could also boost the
voltage to get the current down, and drop it back down in the car. All
things are possible if money is no object. :-)
If you want to go the science fiction route: superconductors.
While they could be used, I think the cooling losses would make it a
very inefficient way to transfer power. Another problem: While
superconductors have no electrical resistance, they *do* have a serious
limitation on current density. If you exceed that current, it ceases to
be a superconductor. A superconducting wire to carry a given current is
*bigger* than a copper wire for the same current.
Massive hunks of copper at the plug
Well, not all that big. The EV drag racers carry thousands of amps
through simple wires and connectors all the time. They just don't have
to do it continuously. Charging at 720kw, the charging time is going to
be very short. No time for things to overheat!
A connector system that surrounds the contacts with a pumped liquid or
compressed air coolant could be very small for a given amount of power.
And very safe -- any flaw in the insulation would cause a coolant leak,
which could be detected very easily.
Just have an industrial robot plug the cable in.
To me, that's the best solution. For one thing, the robots already
exist, as do the people to program and maintain them. Just repurpose
them from the factory floor to the charging station. I also think
consumers would find entertainment value in watching such a robot. You
could also "arm" it, so would-be vandals would be in for a surprise!
"911, what's your emergency?"
"Human, this is robot XYZZY-113. I have captured another vandal. He is
in the canvas bag hanging from the tree at charging station #3 at the
corner of Main Street and 2nd Avenue."
--
ASCII silly question, get a silly ANSI
--
Lee Hart's EV projects are at http://www.sunrise-ev.com/LeesEVs.htm
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