What Are Power Capacitors?


$3,000; Ibuprofen for stress headaches; five weeks of waiting for the car to be repaired – such are the results of the automobile versus deer catastrophe. But what can you say? You didn’t see the deer. So blame it on your faulty headlamps, lack of sleep, hunger, those distracting billboards, or that nice Chevy Camaro SS that zipped by earlier. Meanwhile, the real culprit lays silent – er, rises to a crescendo.

What? The sound system was responsible for hitting the deer? Maybe. Booming bass notes, rising crescendos, and other explosive musical parts demand immediate and powerful energy, which may overload the regular voltage requirements of the automobile electrical system. This causes voltage sag, and leads to dimmed headlights, fuzzy music, and dead deer. How to solve these problems – and potentially save $3,000? Buy a power capacitor.

What Is a Power Capacitor?

A power capacitor (aka “Stiffening™ capacitor”) stores electrical energy. It is not a battery, as a battery produces electricity through the production and absorption of electrons, while a capacitor merely stores them.

A power capacitor has a relatively simple construction. Two conductive substances (“plates”) are placed alongside of a non-conductive substance (“dielectric”), which may be air, rubber or even paper. Incoming electrical current is temporarily stored in an electrical energy field in the dielectric.

When the audio system requires extra jounce, the capacitor can empty its voltage in microseconds, due to its low internal resistance. (In contrast, a battery may take several minutes to dump its load of electricity into the system.) A power capacitor is the perfect augment to an amplifier, which requires vast power boosts to play loud, strong music. If the amplifier is not fed enough volts, it steals power from the lights, air conditioning, engine, and other systems.

The storage capacity (capacitance) of a power capacitor is measured in Farads, named after the legendary Michael Faraday. A one-farad power capacitor can hold 1 amp-second of electrons at 1 volt (Capacitors are not designed to hold electricity at low voltage). Most power capacitors are designed to contain between 1 and 20 Farads worth of energy.

Which to install in your vehicle? The choice of capacitor depends on the style of music listened to, the size and capabilities of the battery and alternator, and the capabilities of the amplifiers. The colloquial rule of thumb is one Farad of capacitance per every 1,000 watts of power with a minimum of one Farad.

Do I Need a Power Capacitor?

If any of the following attributes applies, then you should consider purchasing a power capacitor.

• Headlamps, interior lights or dashboard lights dim when playing loud, boisterous music.
• Extreme bass or treble notes are muted.
• The audio system uses large subwoofers.
• The audio system uses large amplifiers.
• The audio system has a small alternator and battery.

AM radio addicts or those who like “background music” would not be likely to benefit from a power capacitor.

Power Capacitor Tips & Tricks:

When installing a power capacitor, mount it as close as possible to the amplifier so as to minimize cable loss.

If the bass notes sound muffled, don’t automatically assume the amplifier is to fault. Check the installation and location of the subwoofer and confirm that it is arranged in an acoustically beneficial position.

So buy a power capacitor, skip the Ibuprofen, and enjoy the rollicking sounds of a classic rock song played long, loud and lucidly. And save deer.

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