Car Audio Electrical Basics


Car Electrical System

A vehicle's electrical consists of many parts but the ones we're interested in are the battery, the alternator, and the power wiring. A vehicle electrical system is a 12 volt DC system. The primary source of power when the vehicle is NOT running is the battery. The primary source of power when the vehicle IS running is the alternator. This is a very important point to remember. The primary functions of the battery are to start the vehicle and provide power when the vehicle is not running. Because the battery's stored power is so great it is important to treat it with respect. It's the automotive equivalent of a loaded gun. It has the power to stop your heart and can burn your vehicle up if an unfused power wire is shorted to ground. Always remember to disconnect the negative battery cable before doing any work on a stereo system. NOTE: If your radio has a security feature that requires a secret code to be input after power has been disconnected make sure you know this code before you begin (ie Delco-Loc, Eclipse ESN).


Depending on your vehicle's factory electrical system, you may not have enough power to run your aftermarket stereo system. You probably do unless you have a multi-megawatt system or an extremely tiny alternator. If your battery goes dead often after the installation of your new stereo you may have an electrical system problem. Have your battery and electrical system tested by a qualified technician. If everything checks out then you probably are in need of an upgrade. Here are some of the common problems and their likely cures.


Adding a Second Battery

Many people are under the impression that adding a second battery will cure their electrical problems. If one battery is good then two must be better. Wrong. Remember that the function of a battery is to start the vehicle and to provide power when the vehicle is not running. The only thing a second battery will help you with is "parking lot" listening time. Basically it will provide you the additional capacity to run your stereo longer without starting the vehicle. After the vehicle is started the second battery becomes another load on an already overworked alternator. If you do replace your battery I would recommend getting one from Optima ("Red Top" or "Yellow Top").


Upgrading Your Alternator

Frequent dead batteries are a good indication that your electrical system isn't keeping up and you may need to upgrade your alternator. Doing so will give you more juice to run all of your electrical components, including your stereo system, without looking to the battery for help. The problem is your alternator is undersized for your new electrical requirements and has to look to the battery to provide the extra power, resulting in shortened battery life. Have a qualified technician verify this before investing in a larger alternator. Hopefully you can find a larger alternator from your vehicle's manufacturer that will interface with your existing system. Consult the manufacturer or the local dealer to find out about this. If not then you can look to the aftermarket manufacturers to see what is available. Check with Ohio Generator, Stinger or one of the many other manufacturers for high output models.


Factory Ground Straps and the "Big Three"

One of the most overlooked components of the vehicle's electrical system is the factory ground strap. This is the wire that connects the negative terminal of the battery to the chassis of the vehicle. All of the power in the vehicle will flow through this wire so it is a very important connection. Check the connection for corrosion and breakage near the factory ground bolt. You should even consider replacing this wire with an aftermarket wire (at least 4 gauge). Ask your installer or mechanic about making this change. You should also consider replacing/upgrading your engine ground strap and the power wire that runs from your alternator to your battery. The combination of these upgrades is often called the "Big Three".


Power Capacitors

Another solution is to add a power or Stiffening™ capacitor. This device acts as an electrical storage "buffer". It stores power until needed for high electrical demands such as heavy bass notes. If your headlights dim when you have you stereo cranked then you MAY benefit from one of these. This is most noticeable when music with a heavy beat is played. Your headlights will dim to the beat. This is being caused by a voltage drop created by the large power demands of your amplifier(s). A power capacitor will help fill in the gaps in the energy required by your amplifiers. Because of their low internal resistance they can deliver a lot of power much more quickly than a battery can and can often prevent this voltage drop.


Car Audio Capacitor Installation

car audio installation training

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