I always connect my amplifiers power cable directly to the battery. But there is an ongoing debate between a few people on another forum I belong to on where to connect an amps power cable. They are saying that is better and safer to connect it to the vehicle under hood fuse box. Specifically to the terminal that connects the narrow gauge cable coming from the battery. Below is a quote from one guy:
"The battery's main mission is to run the starter. It's secondary mission is to help the alternator run the car's electrical safety equipment. Installing an entertainment feed that is "upstream" of the circuitry needed for those missions jeapordizes those missions. This is why you should not only tap into the underhood junction box, but specifically put the entertainment feed ABOVE the feed from the battery to the UHJB."
Now so I can correctly explain way its better to connect to the battery, what is the technical reason why? The vehicle in question is a Saturn S-Series.
I understand his logic but it is faulty. Power does not flow like water; it is not "diverted" by a connection upstream of a demand. You are not robbing the vehicle's electrical system by somehow diverting power from the car, you are simply adding a parallel demand. Plus, you definitely do not want to place a high-current audio system in series with any portion of the vehicle's normal voltage control systems or you might burn them out. Have your friend review Kirchhoff's current law. The battery is used in car audio mainly because it is an easily accessible connection point with a direct connection to the alternator. If it was easily accessible, a connection directly to the alternator would be preferable.
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Support the12volt.comI agree with Dave completely. Tapping power from the junction box is still connected in parallel, and is now running through the small (maybe too small) factory wiring. Suppose you're running a system with 3000 watts rms power. The factory wiring is definitely not up to the task of supporting this extra load. Doing so can cause you to exceed the current rating of the wire, and melt the insulation away, potentially causing a fire.
That's why we stress the importance of upgrading the "big 3" as well as the alternator if needed before installing such a high powered system. As long as the charging system can deliver enough current, there should be no voltage drop issues. Now the battery (which can also be upgraded if desired) can correctly perform it's secondary job of filtering the ac ripple on the alternator's output, maintaining a steady voltage- no need for a capacitor.
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My ex once told me I have a perfect face for radio.