[ausev] Ultracaps

[Gil Dawson]

On Dec 31, 2008, at 10:09 A, Jim Watson wrote:
> I don't know very much about Caps,.. But I do know that they don't  
> take very long to store a charge,...
> Jim

Turning it around, you might have put it, "They charge very quickly."

On Dec 31, 2008, at 8:46 A, Brian Lasseter wrote:
> I prefer some of the Ultra-caps from Maxwell
> Technologies.  You can get nice 15V, 50F caps for $200.  (In a form
> factor about the size of two fists.)

15V is new, I think.  The highest max voltage I had noticed before  
was 2.

The energy stored in a capacitor rises with the square of the  
voltage, so this is huge.  A 15V capacitor can store (225/4=) over  
FIFTY-SIX TIMES as much energy as a 4V capacitor of the same  
faradiddity.

To compare some very rough theoretical maxima...

A 12V battery rated at 200Ah can store at most    12 * 200 = 2,400  
watt-hours

A 2V 50F capacitor can store    (0.5) * (50) * ( (2) ^ 2 ) =   100  
watt-hours

A 15V 50 F capacitor can store (0.5) * (50) * ( (15) ^ 2 ) = 5,625  
watt-hours

Now, that's getting somewhere.  (Somebody please check my figures.)

On Dec 31, 2008, at 12:17 P, Jim Watson wrote:
> I just looked at the data sheet on a 500.0 F, 16.2 V cap. It says  
> that it was designed for car applications. Also this cap that I  
> looked at was around 5.75 kilograms = 12.67 lbs.
>
> E = (.5)(500)(16.2)^2
> I think that is:   E=64,000 WH   ??

I concur (I get 65,610 wh.)  That's 10 times the Farads and a squeak  
more voltage than Jim's example above, so it checks.  I'm telling  
you, this is new.  I looked all over the web (OK, it was a year ago)  
and 2V was the max I saw.

On Dec 31, 2008, at 12:17 P, Jim Watson wrote:
> What would charging this baby look like?? Would you just plug it  
> into the wall for less than a fraction of a second, and be ready to  
> go?

Not quite.  They probably have a max amp rate through the connectors,  
and you'd be limited by your power supply rating.  But there's none  
of that chemical coddling that batteries require.  They'll probably  
let you flow full current from zip to max.  Recharging an UltraCap  
can't be anywheres near so slow as charging batteries.

Contemplate these numbers for a minute.  More energy than can be  
stored in ten car batteries, in a device that weighs less than 13  
pounds and takes but a few minutes to charge.  What could you do with  
that?

From: http://www.priusownersgroup.com/?p=2989
> [A]n ultracapacitor-equipped Toyota Supra HV-R coupe became the  
> first hybrid to win the 24-hour endurance car race held at Japan’s  
> Tokachi International Speedway. The hybrid Supra finished 616 laps  
> of the 5.1-kilometer (roughly threemile) course—19 more laps than  
> the second-place nonhybrid Nissan Fairlady Z. “The Toyota that won  
> was able to deliver energy more quickly, accelerate faster, and use  
> braking generation more efficiently,” says Kevin Mak, an analyst  
> with research and consulting firm Strategy Analytics and author of  
> a recent study that explores the potential for ultracapacitors to  
> complement and possibly even replace batteries in hybrid vehicles.  
> “The days of the large hybrid vehicle battery pack may be  
> numbered,” he adds.


On Dec 31, 2008, at 12:17 P, Jim Watson wrote:
> "all of these products will perform reliably for more than one  
> million discharge-recharge cycles." What does that bit about one  
> million discharge recharge cycles mean?? Does it mean that one full  
> trip in you car completing 1 full charge of the caps is = to 1 out  
> of the million charges possible.

That is how I read it.  Compare to a battery... you get, what?   
Hundreds, thousands at most?  Ultracaps are qualitatively different  
on this point.

> Damn that sounds great!!!

Yes, doesn't it?

So, what's their downside?  Anybody know?



--Gil