Optimizing Your System – Do You Have Enough Power?

Maybe you already have a high powered sound system or maybe you’re considering adding one.  You want to get the most out of your amplifiers, right?  You want your sound system to be totally optimized and sound the best it can, right?  Wouldn’t you like to be able to get every Watt, every bit of clean, undistorted power that your amplifier was capable of producing?  Optimizing the way your audio system sounds starts with making sure each piece of equipment is getting what it needs.

We need to talk about your vehicles electrical system for a minute.  It seems that most people don’t seem to understand it at all.  People seem to think that their vehicle can magically produce any amount of power needed to power whatever aftermarket electronics they care to add.  The electrical capabilities of a vehicle are seldom ever thought about when purchasing new car audio gear, if they are thought of at all.  So we are going to shed some light on this subject and focus on the effects of a high powered sound system on your vehicle’s electrical system.

Let me give a quick breakdown of how a vehicles electrical system works as there seems to be a lot of misinformed people out there.  You turn the key and the Battery supplies power to the Starter.  The Starter then turns the motor and starts the vehicle.  Once the vehicle is running the Alternator supplies ALL POWER to the electronics within the vehicle (yes, the lights on the outside of the vehicle too) and charges the battery.  The only time that the Battery supplies any power to your amplifiers (or anything else) is, are you ready for this?  Drum roll please…., when the engine if OFF!  That’s right; the alternator is the heart of your electrical system, not your battery.

Slightly expanding on what we just said…  If you put a DMM or Digital Multi Meter on the battery (+) and (-) terminals, with the engine off, you should read approx. 12.6 volts.  Once you start the vehicle and let it idle, you will now see around 14.4 volts displayed on your meter.  So what happened?  The battery did not take a quick shot of Spinach and is not big and beefy all the sudden.  You are now reading what the alternator is putting out.  You see… batteries do not and never will, make or produce any power.  A battery is only a STORAGE device.  Once you start your engine and the entire time you are driving, ALL power comes from your Alternator.

We don’t want to get too technical here and totally lose you.  We do have to explain a couple technical terms so you will understand the next part.  So, basic electronics 101… the best thing about electronics is that it’s all math and numbers.  This is so cool because numbers don’t lie.  You can use a calculator and there is no magic to math!  2 + 2 will always equal 4.  You cannot take 2 dollars; add 2 dollars and it somehow magically make 15 dollars.  We all wish it worked that way though.  But this is common sense and you know all this, right?  Similarly, it needs to be mentioned that it takes power, to make power.  This may seem funny and a “duh” moment, but many people don’t seem to comprehend this.  Follow along here and it will all make sense in a minute.  Below are a few electrical letters / terms we will be using.

P represents Power and is measured in Watts

E represents Voltage and is measured in Volts

I represents Current and is measured in Amps

We need to take a moment to discuss amplifier power.  Again, simple math here…  We go out and purchase a 4000 watt subwoofer amplifier (one of those more inexpensive brands…).  Now, if we look at the fuses on the side of the amp, these are there to protect the amp from too much Current, and we can see this particular amp has 2 – 35Amp blade fuses.  Add these together and we get 70Amps.  So, there seems to be 70 Amps of Current protection.  As a rule of thumb, we can figure that this amp will pull 70 Amps of Current and use a 70A fuse under the hood.

Using simple math and Ohm’s Law we can determine how much power our amplifier is actually capable of producing.

P = E * I

P = 14.4 Volts (vehicle running) * 70Amps (what our amplifier is going to draw)

P = 1008 Watts

So, our 4000 Watt amp is realistically only going to do 1008 Watts.  Now, this is assuming it’s getting the full 70Amps of Current and that it is 100% efficient.  By the way, NOTHING is 100% efficient!  No magic here, just simple math, right?  For our 4000 Watt amp to do what it claims it can – it would need 277.78A of current, at 14.4 volts to produce 4000 Watts.

Back to our vehicles electrical system, our stock alternator is rated at say 90 Amps.  Let’s say it is 85% efficient and that we regularly get 76.5A out of it.  Let us figure that 50A of current is what we normally use just for all the basic vehicle electronics (locks, windows, heater, a/c, radio, instrument panel, wipers, etc.).  This leaves 26.5A for our amplifier that wants 70A!  Now we are just talking about our sub amp here, not including the highs amp or anything else.

So what happens when a bass note hits?  The amp has its largest Current draw.  The draw is too big for the alternator to handle.  Your battery tries to help supply the missing power but it can only do so for a short period of time, then the remaining power needed gets pulled away from our vehicles 50A that was being used for factory equipment.  We end up with an underpowered systems and a bunch of issues.  Are you starting to see the bigger picture here?

Having an underpowered system can cause so many issues.  Some of the signs of such a system may include the dimming of headlights, unexplained amplifier shutdowns, or frequent dead batteries because your electrical system can’t keep up.  Some systems can pull so much power that it makes it so the vehicle can barely stay running while the system is playing.

Not correcting the problem can also cause a bunch of issues like damage to amplifiers, blown speakers, distortion and/or shortened battery life.  An underpowered amplifier will begin to clip and cause damage to speakers.  If it is a Class D type amplifier, the voltage drops can seriously damage the amp.

Keep in mind the above numbers are just hypothetical used to show you the math.  Car manufacturers use alternators that are just big enough to operate the vehicle, not to power a bunch of accessories you might add.  They are not going to give you an alternator with 30% extra room for upgrading your sound system.  Ever look at purchasing a new truck from the dealership?  One of the upgrades offered is the “Tow Package”.  This usually comes with a higher output alternator.  This is because it is assumed that you are going to need more power for trailer lights and trailer brakes if you are towing something.  Don’t you think if there was extra room on the factory alternator, they wouldn’t need to upgrade you to a higher output one just to wire up a trailer plug so you could tow a trailer?

So, we can see the effects of what a high powered sound system can do.  So what can we do to fix it?  A lot of this will depend on your particular system and how you use it.

When it comes to powering a high powered audio system, what power addition or upgrade choices do you have?  You can upgrade your factory Battery to one made for high end audio systems.  You could upgrade your Alternator to a higher output model.  You could add a Stiffening Capacitor or “Cap” to help with those deep bass notes.  These are your main options.  There are a few others and there is of course the ability to add a combination or multiples of these.

Batteries - Contrary to popular belief adding a 2^nd Battery is not going to produce any more power.  Remember, they only STORE power.  Each battery in the system that the alternator has to charge will put an additional 15A load on an already overworked alternator.  To correctly add a 2^nd battery you also need to add a Dual Battery Isolator like the PAC-200.  Also, different types (or colors) of batteries have difference purposes; find out which will work best for your vehicle and how it’s going to be used.

This solution is best done if you (a) have extra cargo space for a 2^nd battery or bank of multiple batteries.  (b) listen to your system with the engine off on a regular basis.  (c) listen to a lot of music with small bass passages between the larger, deep bass notes and regularly listen at higher volume levels.  This sucks power from the battery and then gives it a few seconds to begin recharging before the next bass note.  (d) are a Sound Off / dbDrag competitor and will be using a charger on your batteries between competition rounds.

Stiffening Caps – Don’t want to forget the adding of a Cap solution.  We have used and installed Caps over the years and have not found them to be quite as effective as all the advertising would imply.  The sole purpose of a Cap is to rapidly deliver power and then rapidly recharge it.  The key to a Cap being effective is for it to attach right to the amplifiers power rails.  The longer the wires are between the Cap and the amp, the less effective the cap will be due to the added resistance.  The rule of thumb in finding the right size Cap is 1 Farad per 1000 Watts of power.

This solution is best if you (a) don’t have room for a second battery.  (b) listen to your music at a more moderate volume.  (c) have a Class D amplifier and want to help stabilize the voltage to it.  (d) listen to a lot of music with small bass passages between the larger, deep bass notes.  This will give the Cap time to rapidly recharge before the next bass note.

Alternators – High Output Alternators have been around for quite some time.  There used to be companies that would re-wind your stock alternator to give more output.  We do not recommend this as Heat is the enemy of an Alternator and re-winding it will make it run much hotter.  Specialty High Output Alternators are designed to give you the extra output power you need.  They come in a variety of sizes and will usually bolt right into the same holes as your stock one.  Making the upgrade to a high output model easier then adding a 2^nd battery.  Simply remove your stock alternator and bolt up the new high output one.  How do you know when you need to upgrade your alternator?  The general rule of thumb is that your Current demand exceeds 120% of your alternators output, you need to upgrade to a higher output model.

This solution is best if you (a) have a high powered sound system that causes any of the above mentioned electrical signs / issues. (b) are a serious Sound Off / dbDrag Competitor and your Competition Class permits adding one. (c) listen to your music at high volumes with lots of bass.  (d) you tow a trailer AND have a high powered sound system.  (e) have a lot of aftermarket equipment.  (f) don’t have room in your cargo area to add a 2^nd battery. (g) have exceeded 120% of your stock alternators output capabilities.  (h) have measured the voltage, while the vehicle’s running, at your battery and noticed a voltage drop of -1.5 to – 2 volts or more while your sound system is playing at your normal listening volume.

The solutions above are not an either / or type of scenario.  Maybe based on your system and how you use it the best solution might be to add a high output alternator AND a 2^nd battery.  There are also some hybrid Battery/Capacitor designs that might work for you.  With high output alternators, batteries and stiffening caps, each has its place or fits in a certain application.  But more often than not, the real solution is to upgrade to a high output alternator and they don’t cost that much more then adding a high quality secondary battery setup.

In planning for a high powered system, the installer should take the time to look at what the electrical limitations of the vehicle are, and what kind of additional demand will the system put on it and the charging system once your audio system is added.  Contact the specialists at Majestic Music and they will gladly take the time to go over your vehicle and system with you to help optimize your electrical system.

We hope that you have found this information helpful and possibly learned something new.  Please feel free to leave any comments or ask any questions you may have.

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