Power Caps

[boryc]

Ive just installed a 2 Farad Power Cap in my car, it all seems fine but im confused about the actual workings of it without confusing people.
It seems to "turn off" once the reading goes under 12.00, which seems understandable. But ive turned my ignition off and its been around the 14.00 mark and ive waited to see it drop below the 12 mark and turn off but when ive gone back to it a couple of hours later its lit up and back on showing readings of around 12.50, does this seem correct or maybe a malfunction somewhere as im sure ive installed it correctly.

[tom hopkins]

don't want to sound stupid but what the hell are power caps??????
sounds like some form of capacitor but what does it do?