A stiffening capacitor is an extremely large value electrolytic capacitor. Capacitors have the ability (capacity) to store a charge on their "plates". The larger the capacitance, measured in units of Farad, the greater the charge a capacitor can store for a given voltage. Most automotive capacitors can store a stable volts, and are rated from about up to 5 Farad or even more. Capacitors have an extremely low internal resistance to current flow, much lower than that of a battery. Capacitors can therefore charge and discharge power much faster than a battery can.
How does it work?
All capacitors consist of two "plates", separated by an insulator called the "dielectric". Each plate has an external connector. Connected to a source of voltage, electrons are forced onto one plate, and off of the other plate. When the capacitor is fully charged, no more electrons will flow in or out. Disconnected from the source of voltage, the charge will remain between the plates, and the voltage can be measured between the capacitors terminals with a volt meter. A capacitor can store a charge for a very long time.
The capacitor is connected to the positive power line to the amplifier, and then grounded to the vehicle chassis. When initially connected, the capacitor will very quickly charge up to the voltage of the vehicle's battery. So quickly, in fact, that a large spark will occur unless a small resistance is used to slow the rate of charge. More on this in a moment.
Low frequency causes the output transistors in any audio amplifier to remain on and flowing current to the speakers for a longer period than midrange or high frequencies. Low frequency therefore creates the greatest current draw in any audio system. As the source of low frequency in music is usually a drum or bass guitar, the low frequency is mostly in short bursts, or "transients". So subwoofer amplifiers generally draw the most power from an automotive charging system.
When a motor vehicle is running, the power for the electrical system comes from the alternator. Some very high power subwoofer amplifiers are capable of drawing more power from a vehicle's charging system than the alternator can produce. At very high output levels, this can cause the bass "hits" to begin to lose volume, punch, and overall clarity, and can cause lights to dim or flicker. When the amplifier tries to draw more power than the alternator can produce, the voltage in the power line to the amplifier (and everywhere else in the electrical system for that matter) begins to drop. As the voltage in the capacitor is still stable, the drop in voltage in the line will cause the capacitor to push charge onto the power line. This bolsters or "stiffens" the voltage in the electrical system until the transient bass "hit" passes. At that time the demand by the amplifier drops, the alternator brings the voltage back up, and the capacitor recovers its charge. It is then ready for the next bass transient.
This power "reservoir" in the capacitor only works to a point. If the power draw from the amplifier or multiple amplifiers demands so much power that the alternator can't bring the charging system and capacitor back up between bass transients, then reduced bass response and flickering lights will again occur. Adding more capacitance may help, but an alternator with a higher current rating would be a better solution.
Wherever you're on the road with ATV, motorcycle, snowmobile and any vehicle, IT is extremely reliable and long last Stiffening Power Capacitor you can rely on.
Technical Details:
5 Farad Capacitor
Digital Blue Voltage Display
Chrome Plated Battery Post
Lightning LED
