In article ,
"Tha Ghee" wrote:

"Kevin McMurtrie" wrote in message
...
In article ,


Sorry, but a stiffening cap is worthless. Do the math for the voltage
swing on the cap and compare it to that of the battery. The capacitor
is insignificant.

You'd need to be drawing surges over 250 Amps before a cap became
worthwhile, and it would have to be a ****load bigger than a few Farads.
Effort would be better spent on adding a second battery with a very high
cranking rating.

Even handheld mobile transmitters use capacitors of 1F to 5F. Putting a
few F on a high powered audio amp is like waxing your car to make it go
faster.

what makes a cap worthless, in the car system with a lowly 12vrms the cap is
very necessary. I just want to know what you base your statement on??

The car battery is very capable of holding the voltage above 12V. A
capacitor, on the other hand, stores a very small amount of power. It
takes a lot of Farads before you're doing anything significant compared
to the battery at low frequencies. One amp causes a one volt change
every one second in a one Farad cap. If you figure that bass hits last
1/4 second long, you need a lot of Farads before you're helping much.

The flickering lights that some refer to is the car's voltage bouncing
between the alternator's 14.4 volts and the battery's 12.x volts. It's
purely a cosmetic problem. Alternators are slow to adjust and a fully
charged battery barely conducts electricity above 12.7 volts. A
capacitor can help in this case by making the flicker less abrupt,
especially at engine idle when there's not much current involved.

People who find that a 1F cap is needed to stay above 12V or save their
alternator should really check their wiring. The capacitor is only
masking symptoms of another problem. As others have mentioned, ground
cables are often overlooked in inspections. Check that the battery
cables, positive and negative, are in good shape. Check that a mechanic
didn't forget to re-install ground cables after repairs. 10 guage wires
on the engine block and intake manifold are for engine control
electronics only. There are usually large ground cables at the
alternator and/or starter.

And in the original poster's case, I think he just has a crappy
alternator. They're normally indestructable.