2001 Accent

we'll go from cheapest to most expensive:

1. capacitors. they'll help a little bit.

2. batteries. they'll help more.
(both of those are only bandaids and your alt will still run the risk of eventually dying)

3. getting your alt rewound (wouldn't recommend it)

4. getting your alt rebuilt (best cheap option)

5. high output alt (wooaahh expensive)

2001 Accent

When my car is running and I have the music turned up loud, my headlights dim with the music. Do I need a new battery or a new alternator? [CD, MO]
The headlights will dim because of a momentary drop in the voltage level that is available to power the vehicle's accessories, including the headlights, amplifiers, the engine, etc. This voltage drop can be caused by a very large current demand by an accessory, such as an amplifier trying to reproduce a loud bass note.

The first thing to do is to get your battery and alternator checked for proper functioning. A failing battery can place undesirable loads on the alternator, leaving less power for your system.

If the power system appears to be working correctly, an improved alternator may be required for the large current demands of the audio system. When upgrading an alternator, be careful in your purchase, for there are some potential problems. An alternator which advertises a certain output level may only achieve that output at very high engine RPM ranges, for instance. Also, the new alternator must be adjusted to provide an output voltage within a reasonable range in terms of the voltage regulator.

If you find your car will not start after playing the stereo for long periods of time with the engine off, and the present battery is in good working order, then another, paralleled battery could prevent this embarrassing problem.


What is a "stiffening capacitor", and how does it work? [JSC]
Stiffening Capacitor (note capitals) is a trademark of Autosound 2000. However, "stiffening capacitor" (note lowercase), as a generic term, refers to a large capacitor (several thousand microfarads or greater) placed in parallel with an amplifier. The purpose of doing so is to provide a sort of reserve power source from which the amplifier can rapidly draw power when it needs it (such as during a deep bass note). The electrical theory is that when the amplifier attempts to draw a large amount of current, not only will the battery be relatively slow to respond, but the voltage at the amplifier will be a little lower than the voltage at the battery itself (this is called line drop). A capacitor at the amplifier which is charged to the battery voltage will try to stabilize the voltage level at the amplifier, dumping current into the amplifier. Another way to think about it is that a capacitor in parallel with a load acts as a low pass filter See section 3.10 What is a crossover? Why would I need one? [JSC], and the voltage level dropping at the amplifier will appear as an AC waveform superimposed upon a DC "wave". The capacitor, then, will try to filter out this AC wave, leaving the pure DC which the amplifier requires.


Should I install one in my car? If so, how big should it be, and where do I get one? [JSC]
If you have a problem with dimming headlights when you have your music turned up and the bass starts to hit and the engine is running and you don't want to upgrade your alternator, or if the transient response of your amplifier is unacceptable to you, a stiffening capacitor could help you out. The commonly accepted "formula" for determining the proper size capacitor to use is 1F/kW (one farad per kilowatt). For example, a system running at 300W would need a 0.3F (or 300,000uF) capacitor.

To install the capacitor, you should not simply attach it to your power and ground wires near your amplifier, as it will draw very large amounts of current from your battery and could blow fuses (or over charge). Instead, you should insert a small-value power resistor (25 ohm, 1/2 watt) or a 12VDC test lamp in between the power lead and the capacitor, and then charge it. If you use a lamp in series with the cap, when the lamp goes out, the capacitor is done charging. When it is done charging, carefully remove the capacitor's leads from the charging circuit, being certain not to touch the two leads together. You may then permanently install the capacitor by wiring it in parallel with your amplifier (be careful not to short the leads!). Large caps are currently available from some audio dealers, such as Phoenix Gold. You could also try electronics shops or mail-order houses.


What about adding a new battery? Or upgrading the amplifier? [IDB]
Generally, adding a second battery is great if you want to listen to your stereo with the car turned off (and be able to start it again later!). As far as simply upgrading your current battery to a larger model, you may find that this will help solve the problem because batteries like the Optima 800 offer a larger number of cold cranking amps. However, the "response time" between when a battery kicks in a large amount of extra current and how long it takes a capacitor is vastly different.

Although a battery may be able to respond in tenths of a second, bass notes are often much shorter and need current immediately -- which capacitors can supply. The difference between the two is that while the capacitor can supply a large amount of current immediately, their voltage quickly drops making them ineffective -- but by this time, usually the bass note has passed, and the capacitor has done its job of "stiffening" the supply voltage.

Upgrading your alternator becomes a concern when you need a large amount of current from it frequently. If you are always listening to your stereo at a fairly high volume (assume your amp is drawing 20A), and then you use the A/C and a few other misc. accessories in your car, you can get to the point when the alternator can no longer provide enough current to effectively supply the car and charge the main battery. So, the main battery is always supplementing the alternator's current supply, and slowly (but surely) dies a relatively quick death.


taken from - http://www.mobileaudio.com/rac-faq/rac-faq_toc.html

99.9-Percent-Rice

Thanx man, I think I'll be buying a cap. I have considered it before just never really got around to it. I do get a bit of dimming when the bass hits in my car so hopefully a cap might help that out.

I looked into buying a battery once but after all was said and done, I think the cap (1 farad) was about 1/2 the price and much less of a pain in the ass to install.

Thanks again!

2001 Accent

well upgrading the wire from your atlernator to te battery and the battery to the chassis, would probably cure your dimming problem also, using 4 guage wires, factory is normally 8

[ January 05, 2002: Message edited by: 2001 Accent ]