capacitor to handle elec (reduce load on alternator?)

[talldudenumber5]

i see alot about electrical being the enemy so i thought would adding a capacitor, like the ones they use for large car audio systems, (i.e. those farad capacitors in the kits) right by the batterry help. my idea was that you run the alternator wire to the battery and thats the sole wire to the positive then you run a wire to the capacitor from the battery. then on the out side of the capacitor you have the rest of the wires for the cars positive electrical system.
would this help to regulate the power needed since alot of power is not always drawing just need quick power.(intermitant wipers, blinkers) would this reduce the load on the battery(and increase battery life) and in turn reduce the load on the alternator

just a thought i may be totally off on this one

[NiHaoMike]

The real solution is to replace the alternator with a high voltage 3 phase motor (either induction or permanent magnet synchronous), then set up a high voltage battery pack and all the electronics needed to make it work, such as the inverter/rectifier and DC/DC converter. (In other words, make it a hybrid!)

A capacitor by itself won't do much.

[gone-ot]

...yes, "super caps" will help, but only as temporary storage devices for DC-energy.

...but, even then, for maximum energy-DENSITY, a battery device is better suited.

[NiHaoMike]

A capacitor array could let you FAS a lot more since capacitors are very good for peak power. It can even be made to work on 12v (although you'll need many dozen Farads of capacitance), but higher voltages are more practical since energy stored increases linearly with capacitance but increases with the square of the voltage.
capacitor array for starting engine - diyAudio

[gone-ot]

...BIG difference between a CAP and a BATTERY--the battery is basically a 'constant-voltage' source while a capacitor is not, so as a battery is depleted, it's voltage remains basically constant but its ampere output declines; whereas with a capacitor BOTH its voltage and amprere capacity declines as its energy (Ws or Joules) is used.

...one definition of "energy" storage in a capacitor is given by:

Ws = J = (1/2)*(C*I^2)

...where:
Ws = Watt·seconds (US)
J = Joules (Metric)
C = Capacitance, in farads
I = Current, in Amperes

...it's the constant-voltage (CV) nature of batteries that make them better at LONG-term energy storage, but the non-voltage nature of capacitors make them better for INSTANTANEOUS storage of unknown voltage "pulses" (so that ALL of the energy "content" is captured, and not truncated above some voltage threshhold).

[payne171]

There is an sticky about a split pi ultracapacitor setup with high voltage batteries where the capacitors unload during high output situations as well as absorbing more energy from regenerative braking. I don't know if that will help in a car not designed for it, but it points to the possibility.

[Piwoslaw]

I read that using ultracaps wastes 30%-40% of the energy. I believe it was b/c you have to fully charge it, but can usefully retrieve just over half of the stored energy. This is OK when you have frequent charge/discharge cycles, but over longer periods the cap loses charge.

[Phantom]

Chances are that the Cap will not do anything and in audio they rarely help it is better to clean the grounds and make sure the battery is in good working condition. In most situations it would be better to get a larger/more efficient alternator and put a different pulley on it.

[payne171]

No offense, but you are wrong about capacitors rarely making a difference in car audio. In a car audio setup, a big bass hit pulls more amperage than the alternator provides. The battery cannot react fast enough. Without one, your headlights will dim. With one, the capacitor quickly unloads the extra electricity to cover the peaks. They work well as long as they are needed in the first place and are installed correctly. In theory, I can see how they could help. If you have a bettery setup with a lot of capacity and not enough amperage for rapid acceleration, the caps could make up the difference in during a power/acceleration surge, then recharge under light load.