yes a 1farad cap is what you need

 

Before you going to throw money out of the window please tell me what cable diameter are you using?
How long is the wiring?
How old is the battery and which brand?
What kind of fuses do you use?
Your current draw is to big- that can have two causes:
a) wiring to thin (voltage drop)
b) battery worn out(internal resistance to high)

A capacitor will only cover up a bad supply. Fight the causes- don't try to cover them!

Read this:




Seriously, the voltage drop is caused by the resistance of the wiring or from a bad battery. That explains your diming illumination. Have also in mind that the output of an alternator at idle speed is around 50% of the rated output.

 

the wireing is about 15 feet and the wire is a decent size plenty big and the battery is brand new before winter

 

Despite the good advice supplied, a capacitor is not a waste of money in my opinion. If nothing else, it will take away the constant on - off signals being sent to the alternator.

 

ok thanks for the help know i just need a place to put it running out of room

 

Where do you have everything now?

 

Decent size? Decent is no compareable unit, Which size?
Brand new? A lead-acid from Wally? Which capacity?

These informations are pretty useless, look at the size, brand and capacity.

Disconnect your battery and measure the voltage after 24 hours or more disconnected. Than you have the real voltage and the real indicator how good your battery is.

15 feet in- or excluding return? Where did you connect the return?

Did you measure the voltage while running the engine already?

 

Although this is a bit old...I'm still posting

On the Jeep I never had problems and I have ~1000w of class A/B power, less inefficient than class D and I never had problems with lights dimming.

In my opinion no capacitor needed, just a good battery and good wiring (1/0 gauge and good grounds). If you still have dimming, the Big 3 wiring upgrade is a good improvement. You add 1/0 wire from Alt to Battery (positive, fused), Battery to engine (ground) and Battery to Frame (ground).

 

I tend to agree with Deezel Stink3r... Find the problem instead of band-aiding it... I've always wanted to up the alternator amps and get a better/new battery (instead of K-Marts cheapest one)... The capacitor will just help save the equipment already in existence... And YES, no less than 1 farad... I want to say 1 farad is for 500 watts and under... 1.5 farad would be for 750 watts and under... 2 farad for 1000 watts and under... and so on... Don't quote me on that, but i THINK that's the easy way to figure on the farad vs. wattage...

My lights used to dim now and then on my truck, I changed both battery's to brand new 780cca and I have no problems at all now... I'm also only pushing about 200 watts in audio equip.

Good luck with your problem... Deezel Stink3r is pretty electronic savy - worth considering his advice...

 

Deezel Stink3r is correct and is giving great advice. In most vehicles you can NOT install any type of high powered audio and expect the thin factory wiring (as well as some of the aftermarket audio wiring kits) or even the factory rated battery/altenator to be able to carry the additional load placed on your charging system. In some cars, even just a high powered deck without any external amplifiers will cause your car's gauges/lights to dim, it all depends on battery size and condition as well as the gauge and quality of your wiring and the amperage of your altenator.

I have three class A amps in my car for a total of 1825w continuous @ 4 ohms 20-20,000 hz producing 168db of sound pressure with a max of .04% thd. One amp pulls a continuous current draw of 90 amps, one amp pulls 60 amps and the third amp pulls 30 amps for a total of 180 amps of continuous current draw on my charging system...

Prior to installing all of this audio the factory rated altenator for my car was 30 amps and the factory rated battery was 650cca...

I now run a 110 amp altenator with oversized heatsinks and a 1000cca under the hood. I have two more 1000cca batteries mounted in my trunk. I run 4 gauge many stranded wire (for low resistance) between my altenator and battery under the hood as well as from that battery to the batteries in the trunk. I short-ground my trunk batteries directly to the frame through the bottom of the trunk and I run a 4gauge ground wire back to the underhood battery. I also have two 1farad caps on my sub-amp and a third 1farad for the other two amps...

Depending on how long I keep the volume cranked, I can still make my lights dim as I simply draw too much current however, before I made the upgrades to my charging system I couldn't even get my music volume more than about a third as my amps would go into protect mode... and yes, that was with the caps

So do the caps help?.. Yes.. But only in short music spikes/peaks/bursts... caps will NOT solve a current overdraw problem on your charging system