[pejoculant]

There most certainly are capacitors available that meet his specs without being unreasonably large. For example this one has a capacitance of 1200F and is only 8 cm long: http://www.mouser.com/ProductDetail/Ioxus/RSC2R7128LR/?qs=cf...

Modeling it as a parallel plate capacitor with a mica dielectric is basically totally ignoring the part about it being a supercapacitor. He may as well have been seeing if it would be feasible to get to the moon using a wood fired rocket.

[benjamincburns]

Most supercaps are rated for very low voltages (this one is only rated for 2.4V), as dictated by the breakdown voltages of the dielectric and its manufacturing tolerances. A 6V-rated 1200F supercap made from the same materials will be considerably larger. Further, most electrical engineers will enforce a factor of safety beyond the manufacturing tolerances . This is doubly true for capacitors, since dielectric failure on high energy caps can be somewhat catastrophic (read: explosive).

[venomsnake]

Why would you need 6v for a phone? I got feeling this was pulled out of his ass. Everything works on sub 2V there if I am not gravely wrong (not sure for the light source for the display)

[benjamincburns]

You don't. I'd bet most of the voltage rails on a modern phone are 1.8V and 3.3V. Then the display backlight usually uses a constant-current regulator, and you'll probably have some oddball low voltages for the CPU core and other various things. Given Ohm's law you can generate all that using DC-to-DC converters.

[cheald]

My old HTC Sensation drew 3.7V.

http://www.amazon.com/Anker%C2%AE-1900mAh-Li-ion-Battery-Sen...

[ISL]

High efficiency DC/DC converters are now commonplace. Energy density (J/m^3 and J/kg) and internal resistance are the really important quantities in energy storage capacitors.

[benjamincburns]

Agreed. I discussed this elsewhere:

https://news.ycombinator.com/item?id=5799723

https://news.ycombinator.com/item?id=5799713