I have a 03 and wanted to know if the stock alternator and battery setup had enough to handle a kenwood 300amp class D and 2 10" subs, or do i need a capacitor?

 

Upgrade your big three first, and then see if you need a cap.

But, to answer your question, you shouldn't need one.

 

What does upgrade my big three mean?

 

Main current cables in your car.

The BIG 3

1. The Altenator to the Battery
2. The Battery to the Chasis
3. The Engine ground to the Chasis

 

You replace the ones you have with a bigger gauge wire so that current can flow better.
This makes the car run better in general, especially when you have a big sound system.


edit: Ooops.. Sorry about the double post. I wanted to edit, but I guess I quoted myself

 

300 watts should be fine on that alt. im running 1200watts in mine

 

I'm running a 1000watts rms, but i also have a 10 farad cap...if you run the 300 on the stock, it will work, but most likely your lights will dim, and your amp will not be able to put out as much power as it should. if all you are going to put in is a 300, then i would get a small cap. (i.e. .5 farad or 1 farad)

 

Enough with the freakin' caps already....

A CAP WILL NOT DO ANYTHING!!!!!!!

The definition of a Farad is:

1 Farad = 100 joules or 100W/second

Even with the a 10 Farad cap like cochrand has, it's still not useful.

Reason?

Figure you're running a 1000W rms system Let's assume the best case scenario; that you're running a single Class D amp. these amps are about 75% efficient, which means that at full power, this amp will actually draw 1333.33 watts from the cars electrical system (1000 / 0.75).


So you pop in your Outkast CD an start playing "I like the way you move". The song is pretty bass intensive in the first 10 seconds. with bass tones lasting over 3 seconds each

Remember, 1 Farad = 100W/second, so 10 Farads = 1000 W/second. This means that within 3/4 of a second, your huge 10 Farad cap will be completely depleted. GONE. SPENT. EMPTY!!! And you still have 2.25 seconds of bass left in the note. Guess what's gonna happen to your headlights?

Ok, the bass hit is done! What happens now? The alternator has to recharge the cap while still playing music! So the cap is halfway charged, your alternator is strained because it hasn't stopped producing current and it's starting to heat up, and guess what? Here comes another 3 second bass hit!

Seriuosly, for best performance, Upgrade your wiring, get a better battery, and finally change your alternator if needed.

Main reasons to get a cap are:

1. Audio Jewelry- impress chicks with large cylindrical shiny thingy
2. Extra weight in winter time
3. A very POOR... BUT expensive distribution block
4. A projectile in the event of a crash
5. Rolling pin--for cooking purposes
6. A neat thing to tell your friend, "..Hey man, lick the top of this..

 

^^^^^^^^^
Ding, ding, ding!!

 

caps are useless...get a ho alternator and youll be good

 

ok...it seems that OmegaBlack has a little bit more knowledge than me, but with all that said, with my rediculas cap that i have in my car...my lights don't dim, and my volt meter never goes below 14.3 with the car running...

cap or no cap, if you are only going to put a 300 watt amp in your car you shouldn't need a cap, new alternator, or upgrading the ground wires. Your 300 watt amp is going to pull what, 40 amps? I'm not sure, and Kenwood doesn't say on there web site.

 

7. Some come with bad azz digital volt meters on the top. Roll your pillsbury doughboy **** with that!@

+10000000000 for upgrading wiring.

 

Thank you!! Someone who knows what they are talking about. I was going to reply without reading all the posts, but I'm glad I read them because that saved me some time.

The amount of people that "swear" by caps is truly astounding. Save your money for something else completely useless.

Or send me the money that you would spend on the cap and I will draw out a cap on a piece of paper and send it to you. You will get similar results either way.

 

This isn't entirely correct. First of all a watt=joule/sec and I'm not sure where you get a farad equaling any of that.

Energy stored in a capacitor = 1/2(Capacitance*Voltage^2) which a 1 farad cap @ 14v is about 100 Joules.

How fast a cap discharges depends on a few variables and is a bit off topic. It also recharges just as fast.

A 1000w rms amp doesn't push 1000w rms except with a clean sine wave at the frequency band it was rated at. Playing music will usually get you no where near 1000w.

Now I AGREE that a capacitor is just a band-aid to an insufficient electrical system and upgrading your battery/alternator is a better option, but they do work as advertised. I personally have never used a capacitor. I have only upgraded the battery to push 2 jl 500/1s, a 300/2, and a 300/4.

You will have a better benefit from making sure your wiring is large enough for your current draw, making sure your connections are good and tight, scraping your ground down to bare metal, and don't use a factory stud, drill your own and get nut and bolt and a couple of those star washers that dig into the metal. Upgrade the wire between your alternator and battery and your ground from your battery to the chassis. Actually you should run a ground wire that's the same size as your power back to your battery from your amps for max performance. The frame of your car really isn't that great of a conductor.

Now for your Kenwood 300w class D amp. No you should not need a capacitor of any sort. If you have light dimming issues with that amp your battery is not very healthy.

 

I will agree with both since the argument of capacitors goes on and on, but I have used a capacitor in every system I've built and theres virtually no headlight dimming. Really, what I see a capacitor for is that initial head pounding hit. I don't expect the capacitor to last the whole 10 seconds of the bass hit, just the initial kaboom to take the strain off of the battery. The capacitor provides enough power to initially get things moving. Like they say, it's harder to start moving something rather than keep it moving.