Capacitor question

 

Bronze Member
Username: Msully701

Stratford, Connecticut US

Post Number: 17
Registered: Apr-05
When you shut off your car does the capacitor shut off or does it keep pulling, or does it only pull when your amp needs it?
 

Silver Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 853
Registered: Sep-04
The only time current flows thru your cap is when the voltage at its terminals change. When you shut off your car the voltage drops from about 14 volts to 12 so for a small period of time the cap "discharges" its energy into your battery until the voltage at its terminals reaches 12 volts(or whatever your battery's voltage is). Pretty much the opposite thing occurs after you start your car except that your alternator provides energy to your cap instead of your battery pulling that duty.

Your cap helps your amp by supplying quick "bursts" of energy(current) when your alternator can't keep up and the supply voltage begins to drop. Once discharged to this point to be of further use the cap requires your alternator to raise the voltage again so it can recharge. If the alternator is constantly trying to keep up the cap isn't of much use which is why they don't help at all with extended bass sections, but do help a bit with quick transients like drum hits which have only momentarily steep power requirements.

lol, that make any sense?

-Fishy
 

Bronze Member
Username: Msully701

Stratford, Connecticut US

Post Number: 22
Registered: Apr-05
yes it does, thanks just dont wanna shut my car off 1 night and end up with a dead battery the next morning that would suck :p
 

Bronze Member
Username: Marines

Post Number: 29
Registered: Mar-05
i need 2 know what fared i need 4 my application i have 2 jl audio 10" subs the model is 10W1v2-8 and i have a total mobile audio amplifier 320 watts RMS Total Power and i have the stock alternator in my truck so i need 2 know what i need plzzz advise some 1 (issac) a.s.a.p. if u go to this website www.totalmobileaudio.com the 1st amp that u see when u click on amplifiers will be the amp that i have the T3202 read all the specs and let me know something thank you
 

Bronze Member
Username: Chinaman_87

Houston, Tx Usa

Post Number: 31
Registered: Feb-05
where did you get your setup from, houston?
 

Bronze Member
Username: Marines

Post Number: 30
Registered: Mar-05
larry who are u talking to if u r talking to me i got my set up from auto sound which is a car audio store i didnt let them do the installation because i know how 2 do it
 

TMAGUY
Unregistered guest
You have a total Mobile Audio Amp, new stuff, great bang for the buck, but its only 320 watts RMS. You dont need a cap. Capacitors are for people who want to spend alot of money on something that doesnt do jack sh#^t. Your money is better spent on Good 4 or 2guage power wire and a TRUE ground lug. Those who have actually tested in car with stock alternator see that the dip voltage(not average voltage as found with standard meter) Doesnt increase much at all with a cap. So again, take the money and spend it on wire, and some new JL Audio TR speakers to complement the bass
 

Gold Member
Username: Fishy

Tamarac Ft.Laud, FL USA

Post Number: 1012
Registered: Sep-04
Those who have actually tested in car with stock alternator see that the dip voltage(not average voltage as found with standard meter) Doesnt increase much at all with a cap.

Well duh(and I wouldn't want dip voltage to increase, rather decrease, but I get your meaning).

If your alternator can't keep up with your amps' current demands how the hell would it be able to keep a cap sufficiently charged to be of any benefit? The cap would be good for one lil burst and unless the alternator can provide higher voltage its done with its job. I agree having adequate wiring/ground is a lot more important than having a cap and there is some pretty useless, overpriced stuff out there(high ESR/ESL carbon hybrids, etc.), but I think saying that ALL caps don't do jack in ALL situations is a bit of a overstatement.

A low ESR cap placed close to an amp with adequate gauge wire will provide "extra" current when demands momentarily exceeed what the alternator can provide. Whether this difference is audible is still debatable, but I thought I noticed an added crispness to certain percussion sections after adding mine.

If you've got a couple hours to burn and are really interested check this thread(copy/paste to address line):

http://www.carsound.com/UBB/ultimatebb.php?ubb=get_topic;f=1;t=022965;p=1

It starts getting petty good about page 5.

In fact I'm not entirely sure that those supercaps don't actually help "smooth out" blinking headlights, etc. They just aren't able to provide what I believe to be sufficient current to help with the audible part of the equation.

RC's due back with an in-car test. We'll see what story that will tell.

-Fishy
 

Gold Member
Username: Glasswolf

NorthWest, Michigan USA

Post Number: 7666
Registered: Dec-03
actually, a capacitor's charge voltage directly follows circuit voltage, so if the alternator (power source) voltage drops, so does the capacitor voltage. the only thing a cap can do for you is perhaps increase ransient response time for peak power demands, and eliminate AC ripple from the alternator in the DC voltage rail.
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