Let’s run through a hypothetical to explain this principle. John has a 1,000-watt custom car audio system and he wants to know if the electrical system in his car can fully power it. At maximum output this system will produce 1,000 watts of power to his speakers at about a 62% efficiency rate. So, to determine the amount of input power we need we will have to divide 1,000 by 0.62, or 1,000/0.62. This yields an input power of 1,612 watts.
The Standard Equation For Power Is:
• P= Input power in watts
• V= Input voltage
• I= Input current in amps
Assuming the battery’s voltage is a typical 13 VDC then the input current, or alternator power, needed by John’s system can be determined from the equation to the left.
If we rearrange the equation we get:
And if we plug in the numbers above to that equation we get:
• I= 1612/13
• I= 124 amps
The average output for stock alternators tends to fall in the 60amp range. From this 60amps about 30 will be used to power the car, leaving approximately 30 amps leftover to power your custom car audio system this leaves us with a deficit of 94 amps. Because your vehicle lacks the necessary amperage to power your system you will find yourself being continually disappointed with the lack of performance from what would otherwise be an amazing system.
There are a lot of ways that you can remedy this situation. The first, and most important, modification you should make is to replace your stock alternator with an aftermarket high output alternator. Here at Custom Concepts we carry alternators ranging from 105 to 190 amps at full load. When you begin comparing aftermarket alternators there are several questions you’re going to need to ask yourself:
Will it fit?
Some high-output car audio alternators will replace your original stock alternator bolt for bolt. If the alternator you selected doesn’t do this then you’re going to need to construct custom brackets, a time-consuming and expensive task.
What is the current rating?
This is the most important specification you’re going to want to look at. This is because the ratings for a “hot” alternator match the needs of your system. Typically alternators lose power as they heat up.
Does it have internal or external regulation?
We recommend using external regulation because it’s easier to make adjustments to the electrical system voltage.
Another solution to your problem is to run multiple batteries. These extra power sources will supply the additional energy needed to power your system to full strength when the current requirements of the amplifiers exceed the peak output capacity of the alternator. Having multiple batteries will also allow you to play your custom car audio system for longer when your car is parked and turned off.
The Ideal Situation:
The best situation is to combine both a high-output alternator with multiple additional batteries. We recommend using the largest alternator you can fit on the engine and an additional battery for every 500 watts of power amplification needed.
Types of Batteries:
Now, there are many types of batteries available to you and determining the right one is a very important decision. For custom car audio systems, we prefer using deep-cycle marine batteries. Easily obtainable from almost any dealer and costing around $60, these lead-acid batteries are preferred over calcium based, or maintenance free, batteries because they possess superior internal characteristics.
Calcium based batteries tend to produce large amounts of power for limited periods of time which is a great feature for starting your car but not when you’re looking at long-term use of a high powered car audio system. Compare this to deep-cycle marine batteries and you’ll find that the lead-acid batteries are built to provide moderate to large amounts of energy over long periods of time. The internal plates in each cell are thicker and are built for deep, cyclic use. This becomes important because this design allows you to severely deplete this battery without damaging it, an ideal situation for custom car audio situations.
When selecting a battery there are three ratings you need to look for:
CCA: CCA, or Cold Cranking Amps, tells you the battery’s capability of providing large amounts of current in short bursts at low temperatures. These are best for batteries that you need to start your car
AH: AH, or Amp/Hr, tells you how much current that battery can delivery over a given period of time. When building a high-powered car audio system you’ll want to find a battery that has the largest rating you can find. Typically, deep-cycled marine batteries have ratings between 85 and 105.
Reserve Time: This rating tells you about the battery’s ability to recover and produce electrical current, or energy, after a discharge cycle without re-charging. The longer the better.
The professionals at Custom Concepts recommend installing batteries in parallel. This will result in the most efficient use of their power. When installing batteries in parallel your total AH rating becomes the sum of the AH ratings of all the installed batteries. If you install batteries in this manner they MUST be identical, otherwise you run the risk of one battery discharging the other.
When it comes time to wire the system together… don’t skimp. You’ve just dropped a ton of money into high performance car audio components and assembling them with cheap wire will defeat the purpose of building the system. We recommend large-gauge wire, and at a minimum nothing less than No. 4 wire. Also remember to have 150amp circuit breakers installed at each end of the power cable running from the front to the end of the car. These will protect your vehicle in the unlikely event of a short.
Be sure to take time and plan out the system you want to build… they aren’t cheap. If you want suggestions or help assembling your dream system then come speak with the professionals here at Custom Concepts. We have decades of experience dealing with high-end custom car audio installations and are happy to help. Remember, here at Custom Concepts, we do it right the first time!