I was just wondering if there is a big difference between the various brands of caps? I am thinking of picking up a 2.4 off of ebay for around 100 shipped, just wondering if there are differences between them?

I am not using it like a band-aid though, I am gonna get one just in case I ever need it, I probably dont need it, but it might help some day. I have a HO alt. coming in the mail this week and next payday I was gonna pick up a cap and an SVR battery.

 

I had a generic Cap to stop dimming in my old car. It worked for about 6 months then it didnt do any good except give me a voltage readout. Now I have a stinger 1F cap that i probably don't even need (i used it in my last car and my Si, not the same cars that had dimming) that has been going strong and making the bass sound cleaner for like a year. So yeah, i think brand matters, or at least that its a good brand. Also, better caps have charging circuitry in the top so you don't need to use a charging bulb or resistor, and never have to worry about it losing a charge.

 

Brand does not matter, only ESR. The crappy cheap caps normally have bad esr values for car audio. So there is a catch.

 

what brands do you recommend.?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SilverDc2 &raquo;</TD></TR><TR><TD CLASS="quote">what brands do you recommend.?</TD></TR></TABLE>

Anyone that is legitimate and advertises an ESR I would go with the older companies for this type of thing though. Stinger, RF, etc.

 

What is ESR??? and what is a good value for the ESR level to be at?

 

ESR is equivalent series resistance. It is basically loss incorporated with the operations of the capacitor. The problem is the more current you try putting through a resistor the more voltage loss you get. Most descent caps are about .017 ohm esr.

When a cap is being charged it should charge at vehicle voltage. The cap does not discharge until you pull enough current from your alternator to cause a voltage drop, let's assume 14.4 standard. So if you have 90 amp alternator and pull 100 amps, the voltage will drop to battery voltage, and the battery would back you up for the additional 10 amps. The cap basically gives you a little extra current and higher voltage(14.4) than the battery.

If you are pulling some extreme current, like 200 amps, with a 90 amp alt with a cap this time. The voltage drops, then the cap kicks in (14.4 volts). Now your cap needs to provide 110 amps. ESR causes a voltage drop from 14.4.
110 amps*.017ohms=1.87 volts.
So your cap delivers the voltage at 12.53 which is below battery voltage for a charged battery.

That was an extreme example but illustrates why caps are only good if your electrical system can keep up.

In a nutshell remember the following. Current is always pulled from the highest potential(voltage) in the system. Order generally goes alternator(14.4), cap, battery(12.5-13.0). When the capacity of any object is exceeded it goes to the next. Lower ESR means less voltage loss.

Additional notes, you will see esr as heat generated by batteries and caps during charge and discharge. If your system is too big for your alternator, you may be better off without the cap. It can become another waste of energy.

 

Ok, so if I do get a cap, would it be OK for me to wire it up before the distribution block, or should I put it between the distribution block and the subwoofer amp?

 

Before distribution block is fine.