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post #1 of 4 (permalink) Old 07-13-2002, 07:24 PM Thread Starter
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Dimming lights - Cap or Battery???

The question of what to do when the headlights are dimming has been asked a few times. It usually boils down to a debate on what is better to do to solve the problem. Do you add a capacitor, or battery? I came across an article and thought I would share a piece of that with you all. I found it very interesting. Enjoy.

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The first place to look to determine whether or not you car's charging system is cranking out enough power is the alternator. If you can see the alternator in your car -- not easy in some modern vehicles which are tightly packed under the hood -- the "hot" power rating may be listed somewhere on the unit. If you can't see it, go to an autoparts store or car dealership and ask them to look up the stock alternator on your vehicle. The hot power rating will tell you how many amperes it will produce when the motor has reached its operating temperature.

Once you know how many amperes the alternator produces, assume that the power is sufficient to power the vehicle's standard electrical devices with maybe ten amperes to spare. Now think about how much current draw your new system will add. If the number is greater than ten, then you should think about beefing up the charging system.

If you need only a small amount of additional current, the easiest way to enhance the charging system problem is to replace your existing battery with a larger one. This will allow the audio system to pull the power it needs on rare occasions when the alternator can't carry the entire load. But remember that this solution is only recommended if your charging system needs a slight boost, about 10 amperes. Pulling power from the battery too often will cause the battery to weaken more quickly than it should, and no one enjoys a dead battery.

Batteries are rated by the amount of cold-cranking amperes they produce. A small import car is likely to have a battery rated at 500 CCA. A large battery would have a CCA rating of 1,000. How big a battery should you install? Most experts say get one as the available space will allow. If your vehicle's charging system is significantly short on amperes, then adding a bigger battery will only create additional problems. Adding a second battery is an option, but is not recommended for a variety of reasons.

"I think multiple batteries are a bad idea for vehicles that are daily drivers," says Jeff Triplett, director of technical services for Memphis Car Audio. "A second battery has to be charged by the alternator just like the primary battery, so you're just creating more work for the alternator. If the motor is off and the system is running off battery power, the multiple batteries are OK. However, daily drivers simply have little to gain from multiple batteries."

Another strike against having multiple batteries is the safety issue. Batteries can be dangerous if improperly installed, so great care should be taken if you are thinking of putting in a battery in a non-stock location. Consult a qualified installer if you feel you must have a second or third extra battery.

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A capacitor is a good solution for the quick power response needed for bass-heavy sound systems. A capacitor, sometimes called a stiffening capacitor, is a device that stores electrical voltage and releases it as needed. This is extremely helpful when your electrical system is near its capacity and the music you are playing suddenly hits a thunderous, long bass note. A capacitor would release the needed power to meet the demand without stressing the system and then would recharge itself immediately, ready for the next big note. There also are batteries designed to function like capacitors. The Xstatic Battcap is an example. They contain a larger charge (measured in farads) than do most capacitors.

If your charging system is significantly short on current and you need more than a capacitor will easily handle, then the best option is to add a bigger alternator. Alternators are the fastest power source, meaning they can respond to power needs more quickly than the battery or even a capacitor. Of course, adding an alternator is usually a more expensive solution to your power needs; but it also may be the best solution. Again, though, if you decide to install a bigger alternator, then the question is, how big?

"Obviously, you have to have an alternator that physically fits the available space," explains Dennis Moore, who designs and builds ProPower Alternators for his company, The Mechanical Man in Southern California. "The next questions concerns how much of the alternator belt is in contact with the pulley. Small motors tend to have small pulleys. If there is not enough pulley in contact with the alternator belt, then the belt is likely to slip, squeak and burn up more quickly."

Moore noted that a good solution to the belt traction problem is to add a second pulley, called a "backside idler," to increase the amount of belt in contact with the main pulley. Of course, few people have the knowledge and skill required to add a second pulley to their alternator set up, so it's best to seek the advice of a professional installer when considering this option.

Think about your power requirements if you are considering a new alternator. If you are adding an entertainment system that will consistently create an additional 30 amperes or more of current draw, then you probably need an alternator that will provide at least that much additional power. Keep in mind that a big vehicle such as an SUV has a bigger stock alternator and can probably handle an additional 30 amperes of draw more easily than a Honda Civic. But as a general rule take a close look at your charging system if you add ten or more amperes of current draw.

For the full article, click here.
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post #2 of 4 (permalink) Old 07-13-2002, 07:43 PM
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Nice article. Isn't that from this month's CA&E magazine? I think that backs up the argument that several of us have been making about adding caps and batteries to the system...
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post #3 of 4 (permalink) Old 07-13-2002, 10:03 PM Thread Starter
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Originally posted by dbaudiopro
Nice article. Isn't that from this month's CA&E magazine?
Not sure. But I did get it off the CA&E website.


I think that backs up the argument that several of us have been making about adding caps and batteries to the system...
Yup. Another reason I thought I would share it with everyone.
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post #4 of 4 (permalink) Old 07-14-2002, 12:21 AM
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hmm, I wonder how things will be on the Neon, I just pulled the stereo out of the Intrepid today, and started installing it in the neon, IM about 70% done. I have to find a place to hook up the remote wire for the amp. and hook up the LOC. then Im all set. I wonder how much draw it will be on the neon, I think it hurt the trep a bit, I will check things out.
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