Honda Accord Forum - Honda Accord Enthusiast Forums

Stiffening capacitors are simply too small to provide THAT much power. they can provide very little power at an instant, only until voltage is stabilized, but then need to be recharged. They try to resist changes in voltage, but once they are depleted they drop like everything else. Further, you never fully deplete a capacitor since it won't drop below the system/battery voltage. You only get the energy between 14V-12V... which is less than 10% of the capacitor's capacity.

A stiffening capacitor can be of benefit for a system that is already properly sized. If you can already maintain 14V at all times, a stiffening capacitor can help stabilize some minor fluctuations.

Yes, they are grossly overestimated in their benefits and most people just buy and use them because they saw/heard/were told that it prevents dimming or voltage drop.

Quote:

A capacitor's storage potential, or capacitance, is measured in units called farads. A 1-farad capacitor can store one coulomb (coo-lomb) of charge at 1 volt. A coulomb is 6.25e18 (6.25 * 10^18, or 6.25 billion billion) electrons. One amp represents a rate of electron flow of 1 coulomb of electrons per second, so a 1-farad capacitor can hold 1 amp-second of electrons at 1 volt.
A 1-farad capacitor would typically be pretty big. It might be as big as a can of tuna or a 1-liter soda bottle, depending on the voltage it can handle. For this reason, capacitors are typically measured in microfarads (millionths of a farad).
To get some perspective on how big a farad is, think about this:

A standard alkaline AA battery holds about 2.8 amp-hours.
That means that a AA battery can produce 2.8 amps for an hour at 1.5 volts (about 4.2 watt-hours -- a AA battery can light a 4-watt bulb for a little more than an hour).
Let's call it 1 volt to make the math easier. To store one AA battery's energy in a capacitor, you would need 3,600 * 2.8 = 10,080 farads to hold it, because an amp-hour is 3,600 amp-seconds.

If it takes something the size of a can of tuna to hold a farad, then 10,080 farads is going to take up a LOT more space than a single AA battery! Obviously, it's impractical to use capacitors to store any significant amount of power unless you do it at a high voltage.
The difference between a capacitor and a battery is that a capacitor can dump its entire charge in a tiny fraction of a second, where a battery would take minutes to completely discharge.