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Discussion Starter #1
So I'm at the final stages of installing my 4 channel amp (punch 301x). The amp is all hooked up, so is the capacitor. The only thing not hooked up is the 4 gauge main power to the battery and the ground which are insulated and set aside till I decide to take the big step.

I was reading the instructions that came along with the capactor and one of the steps in the installation is charging the capacitor with a circuit supplied with the cap kit. At first this confused me because I figured just hooking it up to the power cable should do this? Then some vague memories of RC circuits that I remember from my college classes on analog circuits kicked in and I thought hmm that may make sense.... The only thing I can figure is that to charge a capacitor you need a circuit with a resistor and a cap in series and to discharge they need to be in parallel (I think). But really I have no idea. Could someone with more expertise please explain this to me? Also any ideas on what steps are involved? Do I charge the cap before connecting it to the amp? Or does that not even matter? Is there something I should be careful about? Obviously I don't want to stick a finger between the two terminals but is there anything else I should watch out for?

Finally, where to ground? I found a hole on the vertical part of the chassis of the back seat which looks good but I wanted to hear some more suggestions.
 

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Discussion Starter #2
HELP!!!

In case anyone cared to know about this:

1. Charge the cap first. There is a circuit usually provided to do this. It is just a resistor connected in series with the Cap. Only thing ot be careful here is not to bridge the two terminals with a metal/highly conductive object. You're fine if you touch them. I would suggest unhooking your battery's negative terminal hooking the cap up to ground and your power cable then connecting the negative terminal again.

2. Disconnet battery negative terminal when cap is done charging. Disconnect the cap.

3. Hook the cap up to your amp.

4. Reconnect battery negative terminal.

5. Rock'N'Roll. Or not, right now I have everything hooked up and I am getting no sound. I don't think it's the cap though because the amp is powered up and I'm mesuring a good value for the voltage across it.

Oh well.
 

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I had a cap in my WRX that was charged properly. Do I need to recharge it before I install it in my STi or is it still charged from when it was in my WRX?
 

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Discussion Starter #5
Technically you should discharge the cap first then remove it then charge it again. The only reason you would do this is because a fully charged 1/2 farad - 1 farad cap is potentially dangerous. If you bridge the terminals its like shorting out a battery except instead of the battery getting hot slowly the energy is released all at once. I saw it demonstrated once where the cap was not fully charged it made a pretty loud noise and sparked. I'm not sure what would happen if it were fully charged but I can't imagine it being a good thing if they recommend you discharge it first.

As for the second question: Doesn't it charge by itself. I'm not sure. I know that purely from a circuit point of view you need a resistor between the battery and cap positive terminal. Which is all the charging ciruit really is, just a resistor.

Any other opinions, I'm just an amateur here so it would be nice to get a professional opinion.
 

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simon13elmont said:
I'm not sure what would happen if it were fully charged but I can't imagine it being a good thing if they recommend you discharge it first.
Ooh, I can field this one. 'Course it was a 1-farad cap, and it was years ago, but I still twitch when I think about it. :wink:

*twitch*

That and the wall outlet voltage that sent me flying across the room are still etched in my mind. Oh, and the time I had 35kV ignition voltage hitting me from a running engine. Now that was fun - kept banging my head into the hood of the car until I had the sense to let go of the plug wire.

*twitch*

Moral of the story, boys and girls:

1) MOUNT the cap.
2) CHARGE the cap. with a resistor
3) CONNECT the cap. to your stereo system
4) DISCHARGE the cap. when (BEFORE) you remove it from the car

*twitch*
 

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The reason you need the resitor to charge the cap is because it offers a very low internal resistance and if you don't use the resitor to limit the current flowing into the cap it may surge it and destroy it and you along with it.

You also don't wanna short out the caps two terminals when it's fully charged cause it's low internal resistance will allow huge amounts of current to flow out of the cap at once without limit. Amperage is what kills, not voltage.
 
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