Amplifier+Capacitor

John*K · 08-04-2003, 08:47 AM

I have read that a "rewound alternator or a second dry cell battery w/an isolater" or a capacitor may be needed when adding amplifiers to a car audio system in order to supply the amplifiers with sufficient power. How do you determine your power needs before the install? I am thinking of adding two amplifiers, one for the sub and one for the rest of the system. Probably a JL Audio amp, but I'm not sure. I want a high quality amplifier.

Diallo B · 08-04-2003, 10:53 AM

A good rule of thumb for adding capacitors is that any system that is pulling 500 watts or more would see a benefit by using a cap.

Part two to that is for every thousand watts you are running you should have a 1 farad cap. (give or take)

If you install a system that is causing your lights to dim when strong bass passages hit then you need a cap.

Keep in mind that I am talking total wattage not RMS.

Last, a cap will save your primary battery. It stores energy so that when those strong passages hit the draw comes from the cap instead of your battery. It also helps to make sure you have all the juice you need available to make your system sound as good as you have it tuned.

djb

John*K · 08-04-2003, 01:44 PM

Is the 2nd battery a better solution? Would a rewound alternator be suitable? I want to make sure that I am not going to kill my battery prematurely, or cause any electrical damage.

Jeff_Krueger · 08-04-2003, 03:25 PM

Keep in mind that a 2nd battery will be an extra load on the electrical system when the car is running. They are usefull however if you like to listen to the stereo a lot without the car running. When the car is running the alternator supplies the juice to the car's systems, engine, and stereo, the battery only comes into play when the car is being started or there is a large draw on the electrical systme which causes the voltage to drop to the level of the battery or below, at which point the battery will then supply current to fill the demand. Once this peak draw is over the alternator must still power everything else while recharging the battery.

A capcitor works must like a battery it stores a set amount a electical energy that can be discharged very fast. Which means that it also is an extra load on the electrical system. The idea in using them is that periods in which the stereo is drawing a lot of power is very brief and the Cap can supply the extra current during the demand, and in between the peaks when the system is not demanding a lot of current the cap will draw power from the alternator and recharge itself before the next peak. It will hopefully act like a buffer just smoothing out the bumps in the voltage between high demand and low demand.

That being said I would personaly choose a high output alternator since the cost would be not too much more than that of a Cap and will provide all the juice the system will need. This all of course depends on the size of the system and how big the stock alternator is. Some cars have beefier electrical systems to begin with. Remember Caps and batterys don't make power they only store it, it would be more logical to just upgrade the source of the power first.

BTW you will be happy with the JL amp, I'm running a 300/4 to power the front speakers (5.25XR comps and a set of 6W0 woofs) and love this thing. It looks good is built like a tank and has an awesome crossover.
Oh, did I mention it sounds awesome too?

Chris Tsutsui · 08-05-2003, 02:27 AM

If it's a single sub and a 4 speaker amp, I don't think you'll need a second battery or alternator change.

If your subwoofer amp puts out like 300w RMS or more, then it could probably benefit from a stiffening capacitor. You could always put the cap on the sub amp only.

Batteries weigh a lot, and then you have to think of where to put it, and then theres more wiring involved. I'd keep things simple since your install doesn't seem like it's going to be too power hungry.

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Leif Wall · 08-05-2003, 10:09 PM

A high output alt is the best upgrade you can possibly make. It was for me. I went from a stock 60amp alt when I had my old system in (around 800 - 1k watts) to a 190 amp alt (around 2k watts, going bigger soon).

Mine came from Dominick Iraggi, look him up on the www.termpro.com web board. Price paid was about $300 shipped. A lot cheaper then an Ohio Gen alt, that's for sure. A lot of places wanted more money for less power. I highly recommend him. Very very good output at idle also.

Also, upgrading your battery ground, alt to battery + terminal, and distribution block ground, to 4 gauge will be beneficial.

John*K · 08-07-2003, 08:57 AM

Quote:

upgrading your battery ground, alt to battery + terminal, and distribution block ground, to 4 gauge will be beneficial.

Hi Leif -

I didn't quite follow this. Is this a reference to changing wire scheme?

Leif Wall · 08-07-2003, 07:38 PM

Not changing the wiring scheme. Usually the stock wires of those 3 are very small. It's not wise to run 1k watts through an 8ga. or smaller wire.

John*K · 08-08-2003, 02:06 PM

Thanks, Leif. I have found out that my Alt. makes 120 amps, according to the manufacturer specifications. I am guessing that this will be sufficient for the sub and a modestly 6-channel amp.

Leif Wall · 08-09-2003, 04:36 AM

Yes, I think so. I got away with around 800 watts or so on a 60amp alt. That was just a Class D sub amp though. Give her a shot.