Supercapacitors and supercapacitor technology is being used to operate the new stop-start technology for passenger cars.
The old conventional lead-acid battery can't cope with the vastly increased number of stop-starts without its lifetime being seriously compromized. So the new type of AGM (absorbtion glass mat) battery has a nano-porous negative electrode forming a supercapacitor, giving it in the order of 20,000 cycles, or better. (Acknowlegements to "Axion-Power").
Peugeot with its diesels is going a slightly different path with a super capacitor module separate from the battery.
In both cases, the supercapacitor is performing the 'start-engine' function, and the battery is performing 'operate-accessories' function.

Leedsman.