Re: Tesla Motors vehicle question

On Oct 21, 7:42 pm, James Robinson <wasc...@xxxxxxx> wrote:
Rick Powell <rkpow...@xxxxxxxxx> wrote:
I have heard the figure $10 for a 5-minute quick charge at 480 v. for
the Altair or similar batteries that could take a quick charge.

Let's put that into perspective.

If you assume that the same amount of energy has to be put into the
batteries as is contained in 15 gallons of gasoline, with a feed at 440
volts, that would mean the cables would have to be able to handle 15,000
amps over the five minute period. That's about 75 times the maximum
current fed into a typical house (200 amps) these days. Those would be
some heavy wires.

To put it in another measure, the charger would have to provide just
under 9,000 horsepower for the five minutes, or about 6,700 kilowatts. I
hope there is nobody else getting a charge at the same time, or the
lights in the neighborhood would really dim.

I've ignored the fact that there is a difference in efficiency between
battery-powered vehicles and gasoline powered, but it wouldn't change
the numbers significantly.

Either they will be providing only a partial charge, meaning the range
would be far less than a typical car these days, or they are working
with a vehicle the size of a Vespa.

There is also the issue of battery life and heat generated during the
charge. Typically, batteries will heat up as they are charged. The
faster they are charged, the hotter they get. With a charge at that
rate, the batteries would get hot enough to set fire to anything
flammable touching them, so they would have to be well insulated (extra
weight and volume to move around) This is part of the efficiency loss of
battery technology. Further, the faster you charge batteries, the
shorter their life. Batteries get expensive, if you have to replace
them every year.

Seems like lots of existing gas stations could get a new service drop
from the nearest transformer to add an electric "pump" at their
facilities. Lots easier than adding a new E85 tank or compressed
hydrogen tank and specialized pump

It wouldn't be a simple electric service drop, but a huge load. It would
be expensive, and much more difficult than a simple E85 tank.

Interesting. I'm not an EE and I haven't done the calc's, but I think
the equivalent energy they were talking about was 2-3 gallons of gas,
and the electric vehicle would be a direct drive with wheel motors
which would be the most efficient use of electricity, not necessarily
the Tesla. If it is required that a charging station be fed by a 30
kv or 69 kv line or similar, there are still ample locations of
existing service stations near such a line. I would think that "self-
service" might not be possible with such large currents due to the
liability issue.

Previously, I thought that "hot swap" batteries which could be trickle
charged at service stations and removed/installed by a custom forklift
would be the way to go in enabling long range drive EV's. It would
require standardization of the battery pack and a removable rear end
mount, also standardized. Preventing theft of the battery pack would
be an issue.

Plug-in series hybrids, with a small gas engine that can continuously
charge the battery on long distance trips, seem to offer the best
short term hope of putting electric vehicles on the road in
significant quantities. The issues with all-electric vehicles are
solvable, IMHO, but it will be awhile before a reasonable solution is
widely available. I have read about the "supercapacitor" technology,
which would solve some of the battery issues, but AFAIK no one (such
as "Eestor" or other developers) has produced a working model with
enough juice storage to run a decent-sized EV.

RP

.

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