hi all, i have just put a jl 12w3 v2 in my car with a kenwood amp and am gwtting a lot of lights fading on low notes, will a power cap help? how do they wire in.
cheers

 

wouldn't bother with a power cap, I have 2 12's powered by a 1k jl amp and they are fine now I have a new battery

have a read of http://www.talkaudio.co.uk/ and see how power cap is a dirty word in the audio scene

 

Do The Big Three: battery neg to chassis, alternator pos to battery pos, engine ground to chassis.

Definitely worthwhile in the scoob, and solved my dimming problems.

Caps will not fix this. They can't possibly fix this.

 

where is the engine ground to chassis?

 

Sorry, why won´t a cap fix this? In my MY98 it was fixed after getting a cap in...and in my opinion it will never be bad to install a power cap (but never one of this hybrid ones!)

 

i agree that they wont solve problems of power supply, if you have problems with your lights dimming then you can still have the same problem after fitment of a power cap.
you willl probably find as already mentioned, you have an earthing issue which you will need to sort out first.
I personally think that a power cap is a good idea as it will supply some extra power when needed, you must have a good healthy electrical system though as you need to remember that it is another thing for the alternator to charge up as well, thus putting more load on your alternator, hopw this makes sense

 

OK, i suggested that there is a healthy power wiring at first. But also with this I had dimming problems, and the power cap fixed it.

 

well i guess if your alternator is in good order i.e good enough to keep a cap charged, then a cap could take some of the strain under extreme load such as heavy bass lines where an amp will want to draw lots more power, i still wouldn't say the cap fixed the problem but rather it masked (by assisting the alternator) it to a point where you couldn't see it anymore

 

Mhh, I personally think while taking out the pikes of the load its easier for the batterie to delivery energy and so it doesn´t take down the whole car system?!

 

If you saw a difference in lights dimming due to a power cap, it'll be because of something else you did. There's not enough energy in a capacitor to make a difference: the 70-odd joules of energy stored in a cap would drive your 500w amplifier for just over 1/10th of a second...

Why caps are a bad idea? They are bloody dangerous, can explode, can mean trouble if someone disconnects your battery then reconnects it without paying attention to a capacitor being in the car, cost a lot of money when a second battery would be a cheaper and better option...

Upgrade the big 3 (for engine earthing, just add more as the scoob is notoriously bad for this - look at the earthing kits that people charge a fortune for, which are ultimately bits of cable) and if you need to, get a new/better battery.

 

A second battery wouldn't charge and discharge quick enough to make a difference, a cap isn't for powering an amp its just a supplimentary device to add more energy when needed, i.e. when the alternator hasn't got enough juice to supply all that it is running.
The battery only starts the car, once the engine is running it plays no more part apart from being topped up with charge from the alternator.
If you really need more power for your Amp's (which in truth most prob do as i dont belive there is one amp out there that will give its quoted output on the input that it gets from a standard alternator. a 1000w rms amp with only 45-50amps input i dont think so!) then put in a bigger alternator so you have more like 90-100 amps spare to be used.
caps can be dangerous i agree, but its all down to the user at the end of the day, you get supplied with a resistor to discharge them its up to you to sort it if you dont trust the people who are working on your car to be able to do it.

 

thank for the input, think ill look at the big 3 and see where it goes from there. cheers all.

 

a good place to start mate, then like you say, see what happens and take it from there.
i have changed my main earth strap from the battery to a 4AWG Oxygen Free cable, 0 AWG main power cable and i have no problems running 2 largish Phoenix gold amps and some quality accompanying equipment.

 

@chiark: You might know that I´m a bit in that stuff (TA.co.uk...)
And, as said above, the power wiring and batt and so on was good, BUT when you see the lights dimming its only the peak loads the amplifier sucks. And that peak loads you stiff with a cap.
If they are to dangerous for you take a cap with electric securing, than anything you said won´t happen.
Even that ones without are not that dangerous as some people might think.
We tested it in our team. Have you ever seen an exploded cap? Its not the problem that it´s an explosion that hits your *** off. It´s just a bit dirty after that BEFORE it explodes you have to do more than just reconnect it or something. There will only be little lightening if you dis- and reconnect the batt without care.
The thing I want to say is that only a cap with a crap wiring won´t help anything, that I agree. But it won´t be bad if you use one ever!

 

Just to throw my 2p's worth in here - a car battery is capable of supplying 100's of amps; it's internal resistance is very low (that's the limiting factor, plus the resistance of the cables). An amp runs off the battery if it's sucking a lot of juice, although obviously the current from the alternator also helps (okay, it runs from both of them).

If you look at the power taken from an amplifier, unless you're running test tones (or maybe sound-off bass type tracks; same thing! )then a 1000W rms amp will very rarely be producing 1000W rms; most likely it will be producing 100W - 500W rms with most music.

I must say I don't have much experience with caps in cars; but I can see why Chiark provides some warnings. Amps themselves have healthy banks of caps, of course, but these are switched via the 'remote' line. I could imagine that with a large cap permanently in circuit there would be a healthy spark when connecting the battery, and this could cause an explosion (unlikely, but possible) of the battery charging gas.

Anyway, ramble over.

Discuss!

 

We'll have to agree to disagree then - if it worked for you, great . I just don't like 'em and think they're an expensive waste of money

 

So, I see it the other way round, but..no problem. EVERYBODY his opinion! So, lets have drink

 

Exactly: you've got experience on your side that shows it worked for you, I've got experience that showed it did nothing for me apart from make me feel slightly poorer.

Drink sounds good - send across a dunkel or possibly a weissbier, bitte

 

If you´re on that Edingburgh event in july I could bring you one PROST!