5411Re: [evworld] Re: Batteries
- Oct 8, 2005On Sat, 8 Oct 2005 10:57:14 -0800, you wrote:
>Hi All,To some extent, I think some of the stumbling-in-the-dark we are doing
>I'm enjoying the talk about batteries. Yes, it's the crux of the matter. A
>while back, I asked a question to the EV lists about the theoretical limits
>to batteries. I got several great responses, but William Kortoff's seemed to
>be the best. I'm reprinting it below:
in trying to bring ourselves up to speed on batteries is not just how
fast this nascient industry is moving, or can move, but also that we
live in these bizarre times where, taken as a whole, our (U.S.)
country's industries and media and government and some populace are
resisting progress and enlightenment when it comes to technologies
that can help obsolete our oil addictions.
That said, these wh/kg barriers are something we should definitely
discuss more. I wish I knew more, such as by attending a conference
that could help bring me up to date.
One somewhat-outdated-but-perhaps-still-slightly-useful perspective is
available as part of this group's files here:
Note that it was prepared for CARB in 2000, and as it ages, it's
interesting to look back on it, as something you've sort of paid-for,
and see how its conclusions hold up.
A top industry person mentioned to me one of these thresh-holds, I
think it was 300 wh/kg for Lithium based batteries, in terms of trying
to devise aerial vehicles. It's been far too long since I looked at
relevant charts (I'm sure others will come up with some good links for
us) but as we continue to make the reasonably-expected-progress on
better "advanced" batteries, these previously-difficult numbers start
to look perhaps reachable. If we go back a few years, it always
seemed like there was a "catch" to the batteries with better energy
density per unit mass.
William responds to you:
>I can't see what practical applications would need 3000 wh/kg.How about "any"? Isn't there some famous quote from Bill Gates not
seeing how anyone would need more than 640K of RAM?
If we specifically look at the aerial applications issue, and how the
US Military has apparently gone somewhat out of its way to deal with a
more advanced battery such as Aerotech's, we can see how the energy
per unit mass issue becomes critical and nearly impossible to put
limits on the benefits of improving the number. If we ever want to
dare to think of moving some aviation away from the present
technology, we'll need to think big with a lot of different
technologies, not just batteries (and let's not forget that ACP's
Li-Ion tzero came about in part due to batteries that were being used
by model airplane enthusiasts).
Since weight is such a critical element in getting better mileage with
vehicles, I think any improvements we can make in weight with
batteries are something I look for.
When I hear "zinc-air", even though I don't think they're always
rechargeable so much as "rebuildable", I think that maybe some of the
"fuel" is being carried outside the vehicle itself (just as an IC
engine uses mass that is from outside (Oxygen combusted with
With conventional vehicles, the fuel weighs something (6-8 pounds per
gallon?) and the powertrain weighs something. Manufacturers have been
in earnest seeking powertrain weight improvements and generally
nowadays advanced engines often seem to incorporate some sort of
aluminum alloy. Likewise, the non-powertrain-relevant aspects of the
car also employ weight-saving measures in some more advanced cars. One
car that stood out about 10 years ago was the original Acura (Honda)
NSX in terms of its use of Aluminum in the frame, and not just in some
more conventional areas. Likewise, some of the recent public-policy
organizations, that are pushing for better-mileage vehicles in terms
of how they can help us all on various fronts, have started mentioning
such issues as bringing more carbon-fiber focus to bear and lowering
the weight of vehicles.
When I think of the specific-energy-by-mass limitations on batteries,
I think about the challenge of creating a charge differential and
holding it and then delivering current to power something. A certain
number of protons and neutrons would appear to be necessary and so it
has always seemed somewhat logical that a Lithium-based approach
(incorporating a lighter-weight element) might hold promise for saving
weight. Obviously, we're going to go through a lot more innovation
than that over the next few centuries in this field and others that
Maybe we should think about developing some of our own data, if none
is conveniently available, though surely there must be some good stuff
around. Just for the heck of it, I'd be curious to see how mechanical
springs stack up (yes, mechanical springs), as well as some of the
other technologies that some group participants often ask that we not
leave out of the discussion, such as compressed air, hydraulic energy
storage, boron, Hydrogen (there must be some fans amongst us) etc.
Some of these are conventional "fuel-users" though, whereas with a
battery or a spring or something, the onboard-mass does not change as
the vehicle is fueled-up or down.
I guess my last thought for now is that at some point one of the
better Lithium cars was mentioned as storing 50 kWh and this is a lot.
That's still less than half a gallon of gasoline, in terms of energy
content, or maybe about 25 times less than what we might find in an 11
gallon fuel tank. I agree with absolutely not shutting the door on
making progress in this area, but it is useful to know what we are up
- << Previous post in topic Next post in topic >>