Question about using a cap in a car

[joecool85]

Well, I'm too cheap to buy a cap, and I don't need even .5 Farads, I really want like .25 or so Farads. So, I'm planning on using 15x15,000uF caps wired together in parallel (for like $35 or so). The question is, does it drain power when the car isn't on? If it does, is it enough to matter?

 

[Nigel Goodwin]

Well, I'm too cheap to buy a cap, and I don't need even .5 Farads, I really want like .25 or so Farads. So, I'm planning on using 15x15,000uF caps wired together in parallel (for like $35 or so). The question is, does it drain power when the car isn't on? If it does, is it enough to matter?

There will be slight leakage, but not enough to bother a car battery.

 

[Someone Electro]

A cars clock will draw more than this.A cap just stores electricetly.So when you pump up the stereo and the cars batery cant cope whith the drain then the cap gives out the charge to help it.This is many on the bass beats betwen the beats the cap charges back up.

EDIT: Oh and its best to keep the cap close to the amp to minemise the resistace

 

[joecool85]

If I had it set up with a relay so it was only on when the car is running, would that be a problem? I've heard you have to charge them before using them, would they discharge from sitting?

 

[Nigel Goodwin]

If I had it set up with a relay so it was only on when the car is running, would that be a problem? I've heard you have to charge them before using them, would they discharge from sitting?

No, because (from what you asked previously!) they are still connected to the battery, so that will keep them charged.

BTW, what are your expectations from this? - most of the in-car audio stuff is up there with 'snake oil' :lol:

 

[joecool85]

I was meaning that if I had it disconnected from battery unless ignition is on. I'm not expecting much of this, its more of just an experiment of something neat I can do lol.

 

[joecool85]

Eh, actually I might just hook it straight to the battery...

 

[stevez]

I think the purpose of a capacitor, in this application, is to make up for the voltage drop from the battery to the amplifier during moments of extremely high current draw. If you place it at the battery it won't do much good. Like Nigel, I wonder just how much benefit you'll derive from this anyway.

 

[joecool85]

It is to make up for voltage drop, you have that right. As far as where I mount it, I think it has a lot to do with resistance of the wires. I re-did my entire grounding on the car so that it now grounds in 6 spots, 2 spots using 4 gauge wire, and 4 spots using 8 gauge wire...instead of the 2 10 gauge wires that grounded it out of the factory. There is very little resistance throughout the entire car's chassis now. I figure that by mounting it right near the battery it will help "clean up" and even out the voltage flow. As far as gains I may see, I'm not really expecting much, I just think it'd be cool I think it may help when my car idles down though. Right now when I idle down and the fan and headlights are on, it will bog down/dim the lights for a second, then kick back up when the alternator adjusts for it. I think the caps would help with this. Worst case, it does little/nothing for me, and I use it later when I finally get an amp in my car. It has been proven that it helps with sound quality of subs, NOT SPL.

 

[Someone Electro]

Its not only for overcoming resistance its also beacuse the batery cant sudely go from near no load to lots of load (chemical is slow)

But since resistance is alo the problem its good to ount it right before the amps power input.

The strong bass takes a lot of power the high freqecys dont.

 

[evandude]

car batteries are capable of very high current; chances are, when your car dims the lights a bit it's going to suck the caps dry very quickly and it probably wont' make much difference. Putting the caps at the battery is not at all the point of using a cap in a car audio setup, as someone already said.

you also have to consider the resistance and the power handling capability of your little homemade capacitor array; those car audio caps are pretty beefy and can take some current, if you're using small capacitors not only are you going to get added resistance in the wires between them, you're also going to have to make sure your capacitors have low enough internal resistance, and can handle the instantaneous current demands that you're trying to use them for.

adding to nigel's snake oil comment... I am not a car audio nut myself, however I have heard the opinions of a few who do a lot of competitions and stuff, and the general consensus I got was that adding a capacitor is nothing but a "band-aid" fix for a more serious, underlying problem with your electrical system (whether it be weak grounding, poor wiring, weak battery, weak alternator, etc) and if you fix that problem instead, there's usually no great need for a capacitor; and that sometimes the cap will just make matters worse.

 

[Someone Electro]

Using lots of litle caps is better than one huge cap.

Beacuse if you wire then togeter whith thick wire it will have an way lower ESR than that one huge cap.

 

[joecool85]

The band aid thing is only kinda true. A cap will help bandaid a poor charging system, but only a little. And there is no way a cap will make it worse. Some argue it doesn't help, but its not getting to make it worse.

Odds are I'll try my idea and see what happens. If its anything good, I'll be sure to post it.