How To: Stiffening Capacitors

This is a related topic to another thread about problems with my HO alt. I asked this question in that thread, but thought it might be a good idea to start a new thread for it.

I am wondering about Stiffening capacitors. I run two 700W Alpine V12's (One for the tower, one for the hull speakers) and one Xtant 1000W sub amp to run my three 10" subs. The two V12's are powered with 4AWG wire and the sub amp is wired with 1/0 AWG wire. Which capacitors do you guys suggest? I know what storage size I need, but is it better to run all three amps off one big cap. or split it up and put a cap. in-line to each amp? Some larger caps. have a distribution block built into them to make the wiring easy and neat. But I've got one 1/0 wire and two 4awg wires. Which caps. would support this setup? What are all your suggestions on brand, size, setup and wiring/Distribution.

Thanks for your help guys!!!

how long are your wire runs? what RMS are those amps? I think caps are a waste of $$$$. sounds like you have solid wiring. do a search on the internet for caps...lots of good info. For every person who doesn't like them there's one who swears by them.

Adam- My runs are very short. All three of my amps are within 3-4 feet of my batteries. The cables that come from the engine are longer. They're somewhere around 7-8 feet. However, they're also 2 O/T guage. The wire from my alt. to the starter solenoid where the positive cable to the batteries is also connected is a 4 AWG. I was thinking of upgrading it to O/T guage. Why do you think caps. are a waste of money? Also, concerning my earlier question, how does a HO alt. strain an engine? Thanks for your help and info Adam!

From an electrical standpoint all capacitors do is add "ballast" to the electrical system. Sounds like you are already using heavy wire on short runs so it's unlikely that you will see a significant improvement with the addition of caps.

Here is a lame analogy. Wire to the amp is like a rope, if it's too small and stretchy it will not provide a solid pull. Adding a capacitor keeps it from stretching (cap goes at the amp not the battery).

Haha never heard that analogy before. What I have heard is caps are like bandaids, they just cover up a problem from something else in your charging systems (not enough amps from the alternator, poor battery, inadeqaute wiring, etc.)

Mikeski's stretchy rope analogy is pretty good! But Ryan's comment is also valid, if a stiffening cap does any good at all it is to provide a bandaid for a poor design or implementation elsewhere in the system.

If the wiring is adequate you won't get much of a voltage drop to the amp. If the amp is designed properly it can tolerate a fairly large drop without any degredation in the output.

My recommendation: if it ain't broke, don't fix it.

Why do you think you need stiffening caps? Can you hear something in the music that you don't think is right? Do you have some test equipment that is telling you that you are getting some high amount of distortion?

If you can insturment a problem, or think that you hear one, then jury rig the caps in before you bother to properly install them. You can lay the caps on the floor and wire them to the amps with a very short run, which is a better electrical case than you will probably get with a decent installation. Run a before and after test and see if it really does anything.

If it doesn't help, don't install them, they will only lead to trouble down the road.

Besides the problems I am having with my alternator, I haven't experienced amy other problems or heard anything in the music to indicate a problem. The HO alternator I have been using doesn't work anymore and there is evidence that it has been getting pretty hot. Some have suggested a cap. in my system but some of you are against them. When I designed and installed my system wiring was a big priority for me. I wanted to make sure the wiring was up to the challenge in the electrical department and it didn't hinder performance. One thing I have noticed is that when I'm bumping the system pretty hard and the subs are cranked I notice my volt meter on my dash fluctuates. Is this normal or an indicator of a problem or the need for additional power storage?

So is the consensus to not use a capacitor? Would adding another battery be a good idea? I've been using my two Optimas for two years now. Could they be getting weak?

Kraig the cap will in no way help with the total current drain from your alternator. Ive got a 1 farad cap and its been in for over three years and has not caused any trouble. I had a misunderstanding when i added it. I most likely would not add one again if i had it to do over again although the cap top makes for a cheap distibution block. The cap cant really hurt anything as everyones amps have caps internally so how could an external cap hurt? It is generally not needed however IF your wire is of large enough gauge. If your voltage from your battery does dip it will extend your play time and prevent clipping as the output transistors do not like it when the voltage heads south.

Sounds to me like a second or third battery would be the key.. something like the optima blue top.. Adding a cap is just going to add another load to your already stressed out electrical system.. I agree with that others that its just bandaid..

a cap is a very insignificant "load" on a system. All it really is, is a "battery" that can charge and discharge in milliseconds. In theroy it should reduce the load on your electrical system (batteries, alt, ect..) The cap should act as a buffer between your amps and yoru boat electrical system. Adding batteries will just increase amp hours (ie. stereo play time w/o engine running)

Just my opinion , but unless your trying to mount your batteries in strange positions, optima's are not worth the $$$. You can find just as good as batteries even better for alot less.

(Message edited by acurtis_ttu on October 06, 2005)

I may add a cap to my system this winter. I am running about 15' of #2 wire from the battery (that's right only one) to a splitter block where I drop down to #4s going another 4' or so. With only one battery and only #2 wires feeding the power blocks there's not that much "ballast" to keep the amps from pulling the transient voltage down. So far I have not noticed a current draw issue but I am upgrading my amps this winter so all bets are off. One could say that I should add lots of batteries and upsize to 1/0 wire but I don't want that much weight in the boat because I still slalom ski and the boat is already a beast. Luckily I have a very good voltage recording meter that measures voltage sags. I will hook it on the boat one weekend, if the voltage drops below a reasonable threshold then I will add a cap.

Audio systems consume electricity in waves, a cap can raise the low point of the voltage swing but it cannot raise the average.

Here ya go, this is all you need

100 Farad 16 Volt Competition Grade Capacitor.