On Fri, 19 Sep 2008 08:01:11 GMT, mauried@tpg.com.au (Mauried) wrote:
>Lithium Ion batteries, whilst still being the best option for electric
>cars, are simply too expensive to be viable, and there is no sign
>of any major cost reductions.
>Lithium Ion batteries will need to drop in price by at least 10 times
>to become commercially viable for EVs.
>Historically, the progress of improving battery technology has been
>glacially slow.
And who wants to buy new ones every year ande a half. Maybe they have
the magic bullet in controllers for cars, but that's the life I see in
laptops. Also, can you imagine the fire supression system that would
be needed? If this all comes to pass, maybe I'd better buy that
standby generator, power cuts may be much more common.
wrote:
>>> 300 miles needs 40 KWH
>Sounds a bit light to me. Do you have any references on this? It has
>always been an interest of mine, as so much petrol replacement talk
>seems to not to consider the amount of energy that is actually needs
>to be replaced.
Ron, there doesn't seem to be anyone in this thread who actually owns an EV. I
do. Several.
My little run-about, a CitiCar, has 16kWh on board. It's good for about 40
miles at 50 mph or perhaps as much as 50 miles if driven in the 35 mph range.
This is a tiny, golf cart-sized car with decent aerodynamics, a direct-drive
drive-train, nice hard, low rolling resistance tires and light weight, as EVs
go, having an aluminum chassis and plastic body.
A converted conventional vehicle such as a Geo or an S-10 pickup will use from
250 to over 500 watt-hours per mile. 40 kWh would take the vehicle 160 miles
at 250 watt-hours per mile and 80 miles at 500 watt-hours per mile. As a
practical matter, because of hills and stop and go traffic, one typically gets
from half to 3/4 the theoretical range. These are low speed vehicles, seldom
topping 60 mph.
A typical conversion has 144 volts' worth of 220 (20 hr rate) amp-hour golf
cart batteries. At the high discharge rate that an EV subjects them to,
they're typically worth about half that.
Production EVs should have better Cds and much better drive trains,
particularly AC motors. The Chevy Volt is quoted in various places of having
a Cd of 0.27 to 0.29 - not all that hot. The GM EV-1 had a Cd of 0.19. Of
course, it was as ugly as the south end of a north-bound mule....
Though the information leaking out is muddled, best I can tell, the Volt will
have a 16kWh pack. If the leaked information is correct, the control system
will maintain the battery's charge between 20 and 80%. IOW, 60% of the
battery's capacity will be available for propulsion. 16kWh * 0.6 = 9.6kWh. If
the Volt can go its claimed 40 miles then the efficiency is 9,600/40 = 240
watt-hours/mile.
The 40 mile range is almost surely quoted over the EPA's standard test cycle
for EVs which tanks into account hills and stop and go traffic. IOW, it's a
realistic range and efficiency.
For a pure EV (no fuel engine), I've been saying for years that a 300 mile
range is the magic number where the average driver simply won't have to worry
about range for around-town driving. It's the magic "comfort number" that
eliminates what GM calls "range anxiety".
I've learned with my EVs not to PLAN a trip longer than half their known
range. The reason is that something invariably comes up that causes me to
travel extra miles. Using the 0.5 formula, I have plenty of head room for
those extra miles without depleting my batteries to a damaging level.
Using that rule, one would have to work extremely hard to drive 150 miles in a
day other than on an extended trip where a BEV isn't appropriate. Even when I
lived in Atlanta and burned up I-285 on a daily basis, I'd be hard-pressed to
do 150 miles.
For a Volt-like car with a PRACTICAL efficiency of 240 watt-hours per mile,
one would need 0.24 * 300 = 72kWh on-board. Actually closer to 100kWh if the
depth of discharge is kept above 20%. 100kWh is not doable at any reasonable
cost right now but it will be in a few years if battery technology continues
to follow an almost Moore's law-like capacity vs cost curve. I can hardly
wait.
Meanwhile my next conversion is under way. It'll have a 60 mile range using
PbA batteries and an on-board generator configured in a discontinuous series
hybrid mode. That is, the generator won't be large enough to supply the
running power but it'll be large enough to replenish battery energy fairly
quickly. A typical scenario will be that I drive 50 miles to the store (I
live in the mountains and the closest store are between 25 and 50 miles away).
I'll do my shopping while the generator recharges the batteries. Then I'll
drive 50 miles back home with the generator still running.
That way I'll drive over half my trip on pure battery power (cheap TVA
electricity) and the other half on very highly optimized engine power. If I
can find a friendly merchant in town who will allow me to opportunity charge
(my paying for the electricity, of course) then I may be able to make almost
all the trip on battery power.
John
--
John De Armond
See my website for my current email address
http://www.neon-john.com
http://www.johndearmond.com <-- best little blog on the net!
Tellico Plains, Occupied TN
Why the US is losing its competitivve edge:"It used to be that the USA was
pretty good at
producing stuff teenaged boys could lose a finger or two playing with."-James
Niccol
Neon John wrote:
> Production EVs should have better Cds and much better drive trains,
> particularly AC motors. The Chevy Volt is quoted in various places of having
> a Cd of 0.27 to 0.29 - not all that hot. The GM EV-1 had a Cd of 0.19. Of
> course, it was as ugly as the south end of a north-bound mule....
I'll bet the (GM) Opel Flextreme will better that by a country mile.
Apparently Saturn in the USA are now looking at taking it too, having just
adopted two other
Opel models, the Astra and the Vectra
http://www.canadiandriver.com/news/08detroit/080114-4.htm
Graham
Neon John wrote:
> A typical scenario will be that I drive 50 miles to the store (I
> live in the mountains and the closest store are between 25 and 50 miles away).
> I'll do my shopping while the generator recharges the batteries. Then I'll
> drive 50 miles back home with the generator still running.
The joy of this of course is that the ICE can be run for optimum efficiency
whilst doing this
job since it doesn't have to speed up and slow down with the vehicle.
In icy weather its 'waste heat' can also be put to good use for cabin heating.
Incidentally, from expereince of my Saab, relatively modest heat seat heating
can hugely
reduce the energy needed to keep comfortable on cold days.
Graham
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>cars, are simply too expensive to be viable, and there is no sign
>of any major cost reductions.
>Lithium Ion batteries will need to drop in price by at least 10 times
>to become commercially viable for EVs.
>Historically, the progress of improving battery technology has been
>glacially slow.