How big do you think these caps are?

[Dusty Chalk]

The "super power caps" that Nissan is going to be using in their upcoming hybrid electric diesel cars that they'll be using instead of batteries.

[aardvark baguette]

I would think we would be talking about at least several dozen Farads.

[Filburt]

They're supercaps; frequently called "double layer" etc. Nichicon lists a series that goes up to 4000F (http://www.nichicon.co.jp/english/products/pdf/e-jd.pdf), although maybe they have some higher capacity ones that they aren't listing. EPCOS apparently makes some 5000F ones. Digikey and Mouser carry Supercaps, though Digikey's selection seems to be better.

[Dusty Chalk]

Correct me if I'm wrong, but the whole paradigm is different -- using caps is like using memory that doesn't last from reboot to reboot, so they'll have to be charged up every time the car is run? Unless they use relays or something that guarantees that there is zero leakage current going through when the car is at rest/powered off?

[aardvark baguette]

Correct me if I'm wrong, but the whole paradigm is different -- using caps is like using memory that doesn't last from reboot to reboot, so they'll have to be charged up every time the car is run? Unless they use relays or something that guarantees that there is zero leakage current going through when the car is at rest/powered off?

Well its definitely different already; I know the car audio people have the alternator & battery recharge their caps. So without a battery, I can only assume that it would be further taxing the alternator. Maybe they have a completely different method of recharge

I should think a major caveat of this design, even if implemented successfully, would be a lack of ability to start the car, turn it off and start again. It seems like it would be extremely vulnerable, if it isnt driven and given time to recharge.

But thats pretty much my limit of understanding on caps; I'm no expert by any means.

I'm also not sure if the charge is fully lost when the car is shut off, even for normal caps. I don't believe it is fully, because the process of initial charge is supposedly tricky, and has to be done just right. Once installed, its more or less just driving and no maintenance from the user end. So I assume they keep at least a nominal charge for a few days being shut off.