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February 21, 2006


Michael Cain

Since I don't think conveniently in Joules, 325 kJ/kg works out to just about 90 Wh/kg. That's a factor of 15 better than Maxwell's current products. I see that the product announcement is for materials; we'll have to wait for someone to deliver big honkin' capacitors made with it. Still, exciting times...

Robert McLeod

Given the density of aerogels (typically milligrams/cm^3) I wonder how big a volume a kilogram of this material would occupy.


Good catch, Robert.

I noticed too that they don't discuss voltage (and a lot of their numbers are stated in terms of 'up to', such as 'up to' 20 KW/kg, whereas Maxwell has a production device that's 10 KW/kg).

One of the sticking points about carbon supercaps is that while they can hold an astonishing number of farads, the theoretical peak voltage is - I believe - around 3.5V (Maxwell's chemistry achieves 2.7V). You have to stack a lot of these things in series in order to achieve automotive voltages, which kills the capacitance.

So, if the ACI chemistry were, for example, 3.2V, that would be fairly impressive. If on the other hand it were 2.2V, it might be competetive, but not such a breakthrough. Of course, if it is close to the limit, one wonders where we have to go from here. You aren't likely to get much higher energy densities with carbon, I don't think. Are you?


Oops. These guys have been shipping carbon aerogel supercaps for a while now. They're pretty small (50F max, it looks like), but they're at 2.5V



At 90 Wh/kg, you could make a powerpack for an electric bicycle which packs 500 Wh (enough for about 30 miles), recharges from a wall outlet in 6 minutes and weighs about 12 pounds.  A 2 kWh surge pack for a hybrid car, 50 pounds.  Woot!

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