Myth of the Magic Car Audio Power Capacitor

Car Audio Power Capacitors A car audio power capacitor is a secondary, passive (non-powered) storage device for electrical power. Sometimes simply called a power cap, cap or Stiffening Cap™. They typically come in cylindrical shapes that are three inches in diameter and about a foot long though rectangular shapes are also available for different technologies. There will be a positive and negative terminal and possibly a third remote turn on terminal that turns an LCD display on or off. Regardless of the shape or extras they come with they are designed for one thing, to store electrical power. Why Does a Car Audio Power Capacitor Work? A car audio power cap works by storing large amounts of electrical power which it can then deliver to power hungry components when called upon to do so. They have an advantage over typical lead acid storage batteries because they have very low internal resistance. This allows them to deliver large amounts of power (current) very quickly. Much faster than a car's charging system can deliver that same amount of current. Car audio power amplifiers have can have very large current demands. This is dependent on the music being played through the amplifier. Typically these currents are only needed in short bursts during transient peaks (cannon shot, bass drum strike, etc.). If the amplifier tries to pull this current from the electrical system directly it may cause a drop in voltage called a sag. This sag is equivalent to a voltage drop in the system and the size of the drop depends on the resistance of the wire from the source (battery) to the amplifier. As an example, let's say you have twenty feet of 8 gauge wire and your amplifier suddenly needs 100 amps for a bass hit. Using Ohm's Law where voltage, or in this case voltage drop, is equal to the current (100 amps) times the resistance. Using a power wire resistance table we can see that 8 gauge wire has a resistance of 0.000739 ohms per foot. Multiple that by the twenty foot length of wire we have to get a total resistance of .01478 ohms. That doesn't seem like much but relative to the voltage of a vehicle's electrical system it is. Here's the math: E = I x R or voltage = current multiplied by resistance E = 100 amps x .01478 ohms E = 1.478 volts So 100 amps running through a twenty foot long run of 8 gauge wire causes the voltage at the amplifier to drop about 1.5 volts. And if your vehicle's system is charging at 14 volts (13.5-14.5 is the "good" range) the voltage at your amplifier will be 12.5 volts. This also shows why you need to know the current draw and wire length in your system. If your amplifier(s) are capable of large current draws on a continuous basis you need to have large power wire to keep this voltage drop minimized. So what does that have to do with a car audio power capacitor? Two things. First, a power capacitor is placed much closer to the amplifiers than the battery is so that voltage drop is going to be much less all other things being equal. But second, your charging system probably isn't designed to provide current draws that large at any time. So your amplifiers are going to have to get the power from the vehicle's battery as well as the alternator. And the battery has its own internal resistance which, as stated before, is much higher than that of a car audio power capacitor. Because of this extra internal resistance it is not an effective means of delivering large amounts of instantaneous current. The capacitor acts like a small tank with a large hose while a battery acts like a large tank with a small hose. So with a capacitor installed you can deliver a large current burst during a music transient and then the capacitor can recharge during the non-peak portions of the music. See the diagram below which illustrates the capacitor as a water tank. The water represents the electrical energy that a capacitor stores. The tank has a slow moving input line which comes from the battery. The tank also has a large output line which goes to the amplifiers. This large output line let's the tank drain quickly. But if the amplifiers try to pull too much out the tank will empty and you will have to wait until the slow input line from the battery refills it. To avoid this you need to make sure your tank is big enough for your amplifiers. This capacity or "tank size" is measured in Farads. Will a Power Capacitor Help You? I don't know, it depends. How's that for an answer? The degree of help a power capacitor will give you depends on your specific vehicle, car audio amplifier(s) current draw, music type and listening habits. 1. If the electrical system has a lot of additional reserve capacity (large alternator and battery) then you will benefit less then one that has a marginally acceptable charging system. 2. If you have large amplifiers with large current draw capability then you are more likely to need a car audio power capacitor. Smaller systems may not benefit at all or at least not enough to justify the cost. 3. If you listen to AM talk radio then you probably aren't going to have large transient peaks in your program material. But if you listen to bass heavy music then you are more likely to benefit from a power cap. This is especially true of classical music which has very large peaks and dynamic range. 4. You can have the biggest amps in the world but if you don't crank it up then you're not going to ever reach the large current draws those amps can require. Of course I don't really know anyone who buys big amps to let them idle. So if your system is being asked to reach loud volume levels a power capacitor can be a good supplement. How Do You Know if You Need a Power Capacitor? The first way most people know if their system is in trouble is headlights dimming. To most car audio enthusiasts with a passing knowledge of electrical systems this means a capacitor is needed. Headlights dimming? Get a cap. And that's a pretty good guess but not always true and certainly not a guaranteed cure. A power capacitor can only do so much. If your electrical system only has a scrape it's a good band-aid but if it's really bleeding you need stitches. And stitches come in the form of an upgraded alternator and battery. If the headlight dimming only occurs at idle then it probably isn't much to worry about and a power capacitor may help. An idling vehicle puts out much less current from the alternator while the current draw from the audio system remains the same. What Size Car Audio Power Capacitor Do You Need? Since the beginning of car audio power capacitor time (late 1980's) the accepted rule has been one Farad of capacitance per 1,000 watts of power with a minimum of one Farad (that last part is often forgotten). I've never seen any details on how they came up with that so I don't know what it's based on. But no one seems to have offered a better guideline so that's what we still use today. More isn't necessarily better but it doesn't hurt either. So Do You Need One or Not? If your system doesn't exhibit any problems such as dimming headlights then it probably isn't worth the added expense. I've done vehicles that benefited tremendously from caps and others that appeared to have not benefit at all. As always the only way to find out is to try it. Though every car audio shop is different it's unlikely that they will let you test drive a power capacitor. An easier way may be to borrow one from a friend that may already have one installed. Just remember to observe the same safety rules for uninstalling and installing a capacitor as you would for a battery (disconnect the negative terminal of the battery, remove the main power wire fuse, etc.). If installing the power capacitor doesn't help with dimming headlights then you either have a faulty charging system or an inadequate charging system. A qualified mechanic can tell you if the electrical system is not charging correctly. Be sure they check the grounds for the battery too. In some cases you can determine for yourself if the factory charging system is adequate even under ideal conditions. Find the output rating (amps) of your alternator and figure about 30% of that may be available for your audio system. Remember that an alternator's output is not constant and the rated output will not be available when idling. The faster the alternator spins the more current it puts out. If you use an underdrive pulley on your engine then the alternator will put out less than its rated current. Now determine the current draw of your audio system under the conditions you will use it. The amplifier(s) manufacturer should provide this in the owner's manual or by request through telephone or email. If you crank it to the max then use the maximum current draw. Otherwise you'll probably want to use the "typical" or "with music" rating. If your alternator is rated at 80 amps then you probably have 24 amps available under ideal conditions. More when current drawing devices like lights and fans are off. This means your typical current draw needs to be less than 24 amps. Anything more than that are you'll be pulling the additional current from a storage device (battery and/or capacitor). Depending on the degree of additional current you need this can cause the dimming headlights syndrome. Small overages can often be helped with a capacitor while large overages need the upgraded alternator and battery.

How to Find Out What Equipment Fits Your Vehicle

A recurring problem many people seem to have is not knowing what car stereo equipment will fit in their vehicle. It's often hard to determine what size speakers you have when the cones are behind factory grills. Even the radio may not be a standard size.Here's how to find out what you've got to work with in your vehicle. HEAD UNIT The vehicle's radio is out in the open and a few simple measurements will tell you if it's a standard size. The most common size is called DIN (German abbreviation for Deutsche Industrie Norm which translates to German Industry Standard). This head unit has visible dimensions of 2 1/8" (50mm) tall and 7 1/8" (180mm) wide. There is no standard for the depth of the unit. Most aftermarket head units are a direct fit for this size and an adapter kit will not be required. A double DIN head unit will often be found in Japanese vehicles (Toyota, Honda, Nissan, etc.) and is the same width but twice as tall as a standard DIN receiver. There are at least two options available for these openings. The first is to use a standard DIN radio in a DIN to double DIN adapter kit. This will allow the head unit to sit in the top half of the kit while the bottom half may have a pocket, an opening for an equalizer or an opening for a second DIN component. The other option is to use an aftermarket double DIN radio as a direct fit. Several manufacturers make this size in at least one model. After that we have to deal with the non-standard sizes used by some American manufacturers such as GM (Chevy, GMC, Cadillac, etc.) and Chrysler (Dodge, Plymouth, etc.). These are commonly referred to as 1.5 DIN or "DIN and a half". Some refer to this size as "GM/Chrysler". These manufacturers also tend to have shallow dash cavities that make fitting a common depth radio (around 7") difficult. Usually the solution is to get an adapter kit for your DIN radio with a protruding front piece. This will allow you to fit the deeper head unit but the front of the unit will stick out and not sit flush with the dash. A good installer can get around this but it can be costly (re-forming/re-routing air vents, etc.). Another solution is to get an aftermarket radio that is built to the same size specifications as the original GM/Chrysler unit. Pioneer makes at least one model that will fit without an adapter kit. Then there are an assortment of very odd sized radios. Older GM pickups have a split unit with the control section near the instrument cluster and the tape/CD section in the middle of the dash. Older Ford Taurus models used an oval radio with the AC/heat built into the same panel. Both of these were overcome with the proper kits. Now more and more new cars are coming out with non-standard sizes and radios integrated with other vehicle electronics. This makes it more difficult to replace a factory stereo with an aftermarket one. This battle between the aftermarket and the OEM has raged for decades but the aftermarket has always found a way to adapt their equipment to whatever the OEM throws at them. It can take some time to design and bring to market these complex adapters but eventually there will be a packaged solution. The good news for consumers is that the quality of factory electronics keeps getting better and many consumers won't need to replace their factory head unit (at least for sound quality reasons). Instead they can spend the bulk of their upgrade money on the speaker system which is where the greatest benefit will be found. SPEAKERS Speakers are a whole different ballgame. There are many different speaker sizes and it's tough to generalize which manufacturers use which size. The most common OEM sizes are 3.5",4", 5 1/4", 6 1/2", 4x6", 4x10", 5x7", 6x8" and 6x9". There are also two ways to mount speakers, top and bottom mount. Most speakers are top mount but some rear deck speakers will mount from the bottom of the panel (trunk side). For those with odd sized holes or holes bigger than the size you want to install you can buy, make or have made an adapter plate. The pre-manufactured models are usually made from plastic. The custom models can be made of several materials but I find the easiest to work with are Masonite (also called hardboard) in 1/8" and 1/4" sizes and the thinner varieties of MDF (1/4"). Anything is possible if you just have the money to do it of course. So that brings us to the real issue. How do you find out what fits your vehicle? The source most people (and many shops believe it or not) use is Crutchfield. For years their catalog was THE reference guide to have on what fits where. And it was free which also made it a very popular choice. Now the print catalog doesn't have the same amount of information but their website does. Using their "What Fits My Car" feature you can choose your vehicle from the drop down menu and it will give you a list of what products will fit your car. For example, using a 1995 Honda Civic Coupe it tells us that the rear deck speakers are 5 1/4" and the front door speakers are 6 1/2" models. We then have to look at the models of head unit to see that we have a DIN size radio (we know because the DIN sized radios show an EZ fit). Here's the link for the Crutchfield "What Fits" page. But now we have an even better tool at our disposal. A couple of the major manufacturers have partnered with MobileToys, a major provider of vehicle information for the aftermarket industry (especially car audio retail shops). Their database lists almost every vehicle made and what fits where. Thanks to the new partnership the consumer can now use this technology. Now these are designed to help you find the partner's products that will fit your vehicle and it does that very well. However it also shows you the size and depth of openings available in your vehicle. Very powerful. The one I like the best is right at MobileToys website. Using our same Honda car we find the same information for speaker size but we can also click on the "Vehicle Details" link and see a popup that shows photos of the vehicle's dash and speaker areas with size AND depth figures. These depth figures are something that we really need to pay attention to. Buy a head unit or speakers that are too deep and you're going to have problems. Armed with this new information you can now find out what components will fit your vehicle without relying on a salesperson for advice. Knowledge is power.

Headrest Monitor Installation

There are a multitude of options for video monitors used in rear seat entertainment. However, LCD monitors installed in the vehicle’s headrests are most common. There are many choices for replacement headrests with pre-installed monitors and factory-matched fabrics. Additionally, there are plenty of opportunities for an installation technician to install a universal headrest screen in the customer’s OEM headrest and still get excellent finished quality results in just a few hours. Now, rear seat entertainment can be installed today without having to worry about special ordering products. With headrest screens that have installation trim kits, installation is easier than ever and only requires a few basic tools. The real importance is to plan the mounting and wiring before you get started so that the installation time is spent efficiently. Getting Started : Step 1: Checking your headrest Before you get started, check to make sure there is enough room inside the headrest as far as depth and overall surface area for the footprint of the monitor and any mounting trim. Then, look at the angle of the head rest posts and make sure that the monitor will mount properly without flaws. Some materials can be harder to work with than others. For example, cloth will not stretch as much as vinyl and can possibly unravel. Vinyl or leather will tear much easier than cloth when under stress. Being careful when preparing and executing your cuts is perhaps the most important part of the installation process. It is very easy to slip when rushing your cuts and there is no correcting the mistake other than making an unwanted visit to your local upholstery shop. This is why it is so important to plan out and clearly mark all of your cuts and the places where wiring will run. After you do a few of these installations, it does get easier. Don't forget to treat each car with the planning that it deserves to ensure a great finished result!