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Why is this cap so big?

So I am installing a new stereo in my truck (I have done custom, high-end installs for years) and am including a power cap as I always do. These caps are standard in the mobile audio world to keep your headlights from dimming and to keep your alternator from being over-worked.

Question: Why are these things so big? I mean, the 10F super cap is just slightly bigger than a "standard" cap where as this one is almost the size of an oatmeal can at only 2 farad.

Just for some additional info, this particular install has a final output of around 1600 watts total.

Why is this so big?!?!?

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Supercaps are made to be used as comparatively long-term power sources, in the same way that you'd use a small battery. Their high capacitance-to-volume ratio comes at a price - primarily that they've got a low charging voltage tolerance, and in general aren't as tough.

That huge cap you've got there is probably an electrolytic type, with a much higher voltage tolerance. Electrolytics can handle reasonable voltages (you can get HV versions too though), but you have to make them pretty big to compare to a supercap in terms of capacitance. They're also quite easy to manufacture, and they can take more of a beating - a must for automotive applications, as I'm sure you'll agree =D.

What telefox said.  Super caps have a very low voltage tolerance (6V or so), but your tanker probably has a much higher voltage limit.

Sometimes bigger caps are just cheaper, too.

Plasma weapons are right around the corner...

Man, I just love good answers!

Next we can move on to if fire has mass or not...

this is a 12V cap :) btw :D It is usually used in cars audio system for the bass system to don't kill the engine/battery when a big bass drops is comming... I think, it has to charge really fast because drums could be at fast BPM...

Here is the answer.

Remembers me at a russian Matrioshka doll. Guess what is inside the smaller cap. ;-)

Is it a tiny smoke bomb?

It will act as smoke bomb when you reverse the polarity of the smaller cap before reassembling it.