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Car Audio Capacitors vs. Power Cells

One of the most common questions when upgrading your vehicle’s audio system with the addition of aftermarket amplifiers and subwoofers is, “Will I need to add a capacitor or second battery to my vehicle?” If you need to add a second battery, then you have to decide if you should add a power cell or if you should pick up a second battery for $60 at your local discount store. Finally, which of these methods will remedy your headlight dimming problem? These are good questions that hopefully I can help you understand, even if you do not understand the physics behind Ohm’s Law.

Your common starting battery is referred to as a “wet cell” battery. Wet cell batteries contain metal plates submerged in a bath of lead acid that, when energized, creates electrons that produce electricity to power your vehicle. Have you ever noticed the corrosion that builds up on the terminals on your starting battery? This is caused by the acid spilling out of the top of the battery. Not only is this dangerous, but it reduces the battery’s performance. Wet cell is a much older technology but it has lower production costs, so car companies include them “factory standard” with your vehicle. When it comes to adding a second battery, I should point out that it is not recommended to mount a Wet cell battery inside the interior of your car, for obvious reasons. No matter what vehicle you drive, somehow I don’t think corrosion and acid would go well with the interior.

Not to be confused with dry cell batteries, power cells use a newer AGM (Absorption Glass Matt) technology which make the cell lighter and enables them to produce more electricity than your average wet cell battery. They are also safer than the average wet cell battery. AGM power cells use the same metal plate construction as the wet cell batteries; however, the lead acid is absorbed in the glass matt so that the acid cannot spill out. The glass mat also immobilizes the acid so that there is faster reaction between the acid and the plate material. The lower resistance and faster acid migration of AGM technology allows higher rates of amperage during normal charging and discharging. As such, AGM power cells cause less strain on your alternator than your factory battery and they produce more power for your system. Best of all, you can mount these power cells anywhere and in any position—because the acid is absorbed in the glass matt, they will not spill.

What size power cell should you use?

Capacitor Wiring

I’m going to use the example of a 1000W RMS system. Certain factors, such as heat and board configuration, prevent amplifiers from operating at 100% efficiency. Let’s say that our amp is 70% efficient (note: the best amps are about 80% efficient). To achieve 1000 watt