Re: Race to build a better battery


"Evgenij Barsukov" <evgenij_b_no_spam@xxxxxxxxx> wrote in message
news:e7ot9l$o9f$1@xxxxxxxxxxxxxxxxxx
Jim Higgins wrote:
On Fri, 23 Jun 2006 02:13:39 -0000, Ed Ferris <none> wrote:

Sorry, you need 100 kW-hr for 400 miles range, which is what you get
with a good gasoline-powered car. 50 kW-hr for 200 miles.

You can charge a second battery while you're driving around on the
first one. Swap batteries (not so simple if they weigh 500kg, though)
instead of recharging in 10 minutes. Say you fill up once a week,
that gives 7 X 24 = 168 hours minus one for charge transfer, 100/167
kW = 0.6 kW, about the same as the Low setting on a 110V space-heater.
If you're driving cross-country you would have to have battery-
exchange stations along the way, or perhaps limit yourself to 7 hrs.
recharging at the motel overnight.

Or do I have the figures wrong again?


The main thing I see wrong is the idea that totally electric vehicles
with 200 mile battery range are even a remotely viable option.

Let's look at the problem closely and take as model case
the above mentioned 40kW motor vehicle
http://www.greencarcongress.com/electric_battery/index.html
see Tepco and Fuji Heavy Ind.
It can go 80km at 100 km/h, which takes 0.8hrs.
So it has 32 kWh Li-ion battery. What is the size?

Presently high-rate Li-ions used in notebooks
are 1500mAh / 3.6V average/ 40 gm, which gives around
135 Wh/kg and 365 Wh/l.
Note that above high-rate cells (rated to 15C discharge so
it can be charged to 80% in 15 min or faster) have much lower capacity
than regulars which now reached 600 Wh/l.

Anyway, staying with high rate cells (which have a chance
to live long enough to be practical), the battery in above
vehicle is going to be 237 kg, and 87 l. Admittedly,
it is a damn heavy battery, but compared to 1.5-2 ton car
that is not too much considering that equally heavy combustion
motor and transmission can be taken out.

Now, to get 200 miles, e.g. 322.58 km, you need to have
4 times larger battery, e.g. 948 kg and 348 l.
This really is close to the limit of reasonable size
because it would take about half the weight of the car.
It could be argued that power capability of such giant
battery would be tremendous, so unless we want a formula-1
race car we could get away with using low-power rated cells
that have about twice higher capacity (e.g. 600 Wh/l).
Of cause than we give away 15 min recharge (hardly possible
anyway as it would require amazing 515kW charge, 2.3kA at 220V),
but 1 hr recharge to 80% still remains possible.
There might be also some weight saving by using large
polymer cells (in my example I used 18650 cells with are small and
have large contribution of steel casing to the weight).

All in all it appears to be possible to make 200 miles
battery that would be about 500 kg and 180 l sized with
1 hr recharge to 80%. Price and charge practicability
remains out of this discussion.
Well, what the hell - using again high-rate type cell
whole-sale price, 3$/cell and 5.4Wh/cell, we get the price
of 1.8Wh/$ and 32*4kWh / 1.8 Wh/$ = 71111$. That of cause
are bare cells alone without power management, charger, safety,
assembly etc. In well running mass production of notebooks
all of mentioned overhead usually adds about 3/4 of the pack
price. So welcome to your 284 000$ 200 miles car battery.
It is possible, but is it needed or desirable is a different
issue.

Regards,
Evgenij

Evgenij,

Thank you for very clear explanation of Li-ion batteries
in automobiles. My understanding is that an electric
car with a range of 200 miles is physically possible.
Many families have two cars, and one of those certainly
could have a range of 100-200 miles.

What makes Li-ion batteries so expensive? They do not
seem to contain precious metals (Platinum, Palladium,
Rhodium, etc.). Could a well run mass-production
operation engineered to produce large capacity batteries
get the cost down 100 fold? Think in terms of 5 million
battery packs of 200 kg each, having a capacity of 200 kWh.
could the manufacturing cost get down to $5,000?

Regards,

Ernie


.

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