On 17/02/13 08:14, Andy Burns wrote:
The Natural Philosopher wrote:

On 17/02/13 03:46, Ericp wrote:

Uni of California announced they stuffed nanotubes
in a lithium battery and found it lasted longer, held three times as
much and charged in ten minutes.

No,. they didn't. read the thing carefully. It had three times the POWER
density, not three times the ENERGY density.

Yes, they *are* talking about 3x energy density in milliamp hours per
gram (as well as discussing charge rates in amps per gram).


compared with carbon electrodes. But I have never seen carbon electrodes
in any battery its been my misfortune to destroy.

And plenty of other people are getting better than that using other ways:

http://en.wikipedia.org/wiki/Lithium-ion_batteries


Note about twice the energy density of this 'new' research using ..air!.

Something is missing, because lets say that standard today technology is
capable of say 1Ah/gm at 3.7v That's 3.7watt hours per gram, or 3.7kwh
hours per kilogram, or 37kwh per 10kg. So an EXISTING car better ought
to be around 10kg!! No WAY is ANY commercial lithium battery anything
LIKE that.

e.g. an uncased pack of lithium cobalt technology

http://www.hobbyking.com/hobbyking/s...po_ Pack.html

gets around 25watt hours in 200 grams.

so about 125 watt hours per kilogram. A factor of at least 10, possibly
37 ...different from these 'claims'

So something is not adding up.

milliampere hours per gram is not power density and its not energy
density. Its current density, and something is not making sense here.


viz "At the meeting, Au said that his research group has demonstrated a
coin-sized rechargeable lithium-air battery with a current density of
600 mAh/g, which is much higher than the current densities of 100 to 150
mAh/g of lithium-ion batteries.

Read more at:
http://phys.org/news/2011-02-lithium-air-batteries-high-energy-density.html#jCp"


But again, without knowing what the terminal voltage is, its impossible
to know what the energy density is.


My 'what a BEV needs' boil down top at least 200Kwh in a battery
weighing no more than 200kg. That should give you an all day driving
sort of range. So a watt hour per gram essentially. For the complete
battery.

current state of the model world batteries are achieving an eighth of that.

Nickel probably less than 1/15th of that.

The world is full of wonderful claims that are couched in terms that
hide the actuality.

I have no doubt these guys have done good research, but by starting from
a **** poor place and using terms that don't mean much in the real
world, its hard to see that the claims amount to much.

As I said, current batteries are about 8 times worse than they need to
be. Even if these are three times better, its still not good enough.

And the question remains. Three times better than what, and in what way?


http://wiki.xtronics.com/index.php/Energy_density

is worth a read.
Petrol 12,200 Wh/kg So at 30% efficiency that's still around 4Kwh per kg.

Lithium ion 130 - 1200 Wh/kg Even at 90% efficiency that's not cutting
the mustard. And nowhere have I seen a 1.2Kwh/kg battery. The lower
figure of around 130Wh per kg is more like what's around.







[Sorry the links are images, the Nano Research journal is dumb enough to
think they can charge £30 for access to their online articles while
giving a free peek at the first page]

http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/000.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/001.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/002.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/003.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/004.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/005.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/006.png


http://link.springer.com/static-content/0.6134/lookinside/935/art%253A10.1007%252Fs12274-013-0293-y/007.png



Read em all and still no answers.




--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.