The Official Capacitor Thread

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Alright so you've been told or think you know about electrical systems. You've got your degree in car audio forum installation. To earn this degree you think that capacitors are evil but batteries are good. You think that current is drawn from the battery and the alternator is keeping the battery charged.

You couldn't be any more wrong on anything you say. Let's apply some simple logic.

Do capacitors store enough charge to be useful under prolonged heavy draws such as long bass hits? Nope they sure don't. They store hardly any energy and if they do store a lot, they have high esr making them useless anyways. BUT if they store almost nothing, that means they draw almost nothing also. So, does it HURT to have them in your charging system? No. It doesn't really make any difference either way. They are basically a digital voltage readout distribution block with a small reserve of power that your amp can draw from for a fraction of a second. The thing that makes them not a big deal, is when your voltage is at 14v+, the capacitor is drawing no current. It charges to the circuit voltage. Since there is no difference of potential between it and the source (the alternator), there is no current flowing between them meaning no drain. Then when the voltage drops, the capacitor immediately begins discharging. Until the voltage climbs again, it does not draw more current because it's voltage falls to the circuit voltage. Once the bass note stops, the alts regulator raises the voltage back up and the cap charges. This is how electronics work. Without a difference of potential (voltage) current cannot flow.

Well wait, batteries are better right? Well, they are actually exactly what you hate about capacitors.... a constant drain. Yes batteries will store more charge than a capacitor, BUT they can never charge to the circuit voltage. This means when your car is on, they are always drawing current. The more batts you add, the more current you draw. The battery has a LOT of reserve compared to a capacitor right? Of course, so after it discharges, then when the voltage is raised where it can charge again, it has to DRAW a lot because it just discharged a lot right? YES of course!

So in short, a battery can save your amp by being able to supply large amount of current for longer periods of time than a cap can, keeping your amps voltage up at levels where it can perform without hurting itself. It also puts a MUCH larger strain on your electrical system than a capacitor every could.

There IS NO replacement for an alternator. Since a battery cannot charge to the circuit voltage, there is no way it could be supplying current until the voltage drops to it's float charge. So how could a battery stop dimming? The short answer is, your old battery had to have high esr and drawing a lot of current. The new battery has a lower esr and draws less current. Other than that, it can't happen.

Forget what you think you know, because misinformation on this site has been rampant and it's clear most of you don't know much.

 
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