Adding high powered amplifiers to your vehicle’s audio system can do amazing things for sound quality, dynamic range, bass response, and your overall music experience.  But they can also be very taxing on the vehicle’s electrical system. You might notice your headlights dimming with the beat of your music or sluggish window motors. But before you start adding additional batteries, capacitors, and high output alternators, you should consider installing the Big 3 Upgrade.

The Big 3 Upgrade is a relatively inexpensive and simple upgrade that increases the current carrying capability in three key locations in your electrical system (hence, the Big 3) by installing larger gauge wire in addition to the factory wire or replacing the factory wire all together.

This post will outline everything you need to know on what the Big 3 Upgrade is, what the benefits are, and how to install it.


What is the Big 3 Upgrade?

The Big 3 Upgrade is an upgrade to your vehicle’s factory wiring in three key locations to allow current to flow more freely and allow you to utilize the full capability of your factory alternator.  Now, you may be wondering..”Why do we care about the alternator so much if the battery is what supplies power to all the electronics?”

Well, that’s only half correct.  The battery is the primary source of power for starting the engine and running the electronics when the engine is off.  But when the engine is running, the alternator is generating a higher voltage than the battery is at. This allows it to charge the battery and makes it the primary source of power for all the electronics in the vehicle when the engine is running.  And this leads us into the first of the Big 3 Upgrades.


Alternator to Battery Positive Connection


If the alternator is the primary source of power when the engine is running, then it makes sense that the wire connecting it to the rest of the electrical system is large enough to handle the current drawn by all of the electronics.  And it is, in fact, large enough to carry the current of all of the factory electronics.

But what happens when we add that large power amplifier?

Now we’ve added a substantial demand on the vehicle’s electrical system connected to the battery, but we’ve done nothing to increase the current handling capability of the wire connecting it to it’s true source of power when the engine is running.  And that is why the wire connecting the alternator charging post to the battery positive terminal is one of the key locations in the Big 3 Upgrade.


Battery Negative to Chassis Connection


In order for any DC circuit to be complete, there must be a return path to ground at the source.  When you ground an amplifier, you connect a large gauge wire from the negative terminal of the amp to the chassis of the vehicle.

But the chassis isn’t the actual ground of the electrical system, it’s just a means of carrying the current to the ground of the electrical system.  Current is pumped into the vehicle chassis by all the ground connections and it is carried to the battery negative terminal by a factory wire that connects the battery negative terminal to the vehicle’s chassis.

This wire is typically quite small, usually around 8 AWG to 6 AWG.  In fact in most cases, it will be smaller than the wire you’ve added to carry the current that your amplifier will draw, making it a key location for the Big 3 Upgrade.


Engine Ground to Chassis Connection


This third key location for the Big 3 Upgrade is not as obvious as the other two but it is no less important.  As I mentioned earlier, the primary source of power for your vehicle’s electrical system when the engine is running is the alternator, and no DC circuit is complete without a return path to ground at the source.

We’ve already taken care of the return path to ground at the battery with the previous upgrade, but where is the return path to ground for the alternator?

The ground “terminal” for the alternator is the alternator case itself and what connects this to the rest of the vehicle’s ground system is a factory wire that connects the engine to the chassis.  


When Should you Consider doing the Big 3 Upgrade?

Your vehicle’s electrical system is designed to support the accessories that come from the factory and not much more.  So to quickly answer this question, your vehicle could benefit from the Big 3 Upgrade any time you add a substantial demand on the electrical system.

I like to use 500 Watts of RMS power as a general rule of thumb for considering the Big 3 Upgrade.  But the nice thing about this upgrade is that it never hurts to increase wire sizes, so if you only have a 250 Watt RMS amplifier but you feel like you might benefit from installing the Big 3, you won’t harm anything my doing so.


Parts you will Need

The kits that you can buy for installing the Big 3 Upgrade are pretty universal as far as being able to use them on different vehicles.  You’ll need to decide on the size of wire you want to use (I like to use the same size wire that I use to power the amplifiers), and whether or not you need to change your battery terminals to accommodate the additional wires.  Below is the list of parts I used to perform the upgrade on my car.


Tools and Supplies you will Need

  • Wire cutters sufficiently sized to cut large gauge wire.  The ones I linked to work best for large gauge wire.
  • Method for crimping ring terminals onto the wire.  I used this hydraulic crimping tool but you can also use a vice or solder.
  • Utility knife
  • Basic ratchets, wrenches, and screwdrivers.
  • Zip ties
  • Split loom


Big 3 Upgrade Kit and Tools Unboxing

In the video below, I open up all the parts I ordered for this installation to see what all comes in the packaging.  We also take a look at a couple of the more specialized tools that will help you get the install done easier.


How to Install the Big 3 Upgrade Kit

The first thing you want to do before you start work on your vehicle’s electrical system is disconnect the battery.  Start by removing the negative terminal, then the positive terminal. At this time, you’ll also need to discharge any capacitors and disconnect any additional batteries you have in the vehicle.

If you need help with how to properly discharge a capacitor, check out this article from Sonic Electronix: How to Discharge a Capacitor.

Now that you have a safe working environment, it’s time to start the upgrade.  You can perform the upgrades in any order you choose.  If you’d like to see how the install is done, check out the video at the end of this post to watch me do the Big 3 Upgrade on my car!


Alternator to Battery Positive Connection

Start by planning the route for the new wire.  You can route it along with the existing wire or you can choose a new path, this is completely up to you and what works best for your vehicle.

A few things you’ll want to keep in mind when choosing the route for the wire is to stay away from any moving parts like belts and fans, and any parts that get hot like the exhaust manifold or engine block.

You should also plan to have an inline fuse holder no more than six inches away from the alternator connection.  This will protect the wire from catching on fire if it ever shorts to ground. Use a fuse that is sized for no more than the ampacity of the wire you are installing, but it realistically doesn’t need to be any larger than the rated output current of your alternator.

Once you’ve chosen the route for the wire, measure out how much wire you will need and attach a ring terminal to the end that will connect to the alternator.

When you connect the new wire to the alternator charging post, you can choose to use both the new wire and the existing factory wire, or just the new wire.  Make sure that no part of the ring terminal is able to touch the alternator case or any other ground location as this will cause a short circuit.

If you will be using a ring terminal on the battery end of the wire, go ahead and attach it to the wire but hold off on connecting it to the battery at this point.


Battery Negative to Chassis Connection

For this wire, you will need to start by choosing the location on the chassis that you want to attach the wire.  You can use the same bolt that the factory connection uses or drill a new hole or use a different bolt location.

In either case, start by cleaning the area with degreaser and scrape the paint away so you have clean, bare metal to connect your ground wire to.  To remove the paint you can use sandpaper or a wire brush drill attachment.

Measure out the length of wire you will need and attach a ring terminal on the end that will connect to the chassis.  After you connect the wire to the ground location on the chassis, it’s important to apply some dielectric grease to the bare metal around the ring terminal and on the terminal itself.  This will prevent rust from forming on the unprotected metal.


Engine Ground to Chassis Connection

Similar to the last wire, the chassis connection for the wire can be made at the factory location or another location of your choosing.  Prepare the chassis connection location in the same way described above. The other end of the wire will connect to the factory engine ground location.

Once you’ve determined where to make the connections, measure the length of wire you will need and attach a ring terminal to both ends.

Use cleaner and a wire brush to clean the engine ground location and ensure you have a solid connection to bare metal.

Once all this is done, you can go ahead and connect both ends of this wire.


Finishing Touches

Now that all the wires are in place, you can connect everything up to the battery.  Start with the positive battery terminal connections and then the negative.

Give your install a final inspection to make sure that all your wires are clear of any moving parts and hot surfaces.  Support long wire runs with zip ties about every six inches.

As an added test to make sure all your connections are good, you can use a digital multimeter to measure the resistance.  First measure the resistance between the negative battery terminal and the engine ground location. Then measure the resistance between the positive battery terminal and the alternator charging post.  Both of these measurements should be less than one ohm.

If you’re not sure how to use a digital multimeter to take these measurements, check out my post on Multimeter Uses and Functions – How to Use a Digital Multimeter.

Check out the video below to see me do the Big 3 Upgrade on my car.



Now all that’s left to do is enjoy your new electrical upgrade.  Hopefully you’ll notice a more stable electrical system with no more dimming headlights and a better performing audio system.  Let me know how your Big 3 Upgrade goes or if you have any questions in the comments below.

For some additional ideas on how you can upgrade your vehicle’s electrical system, check out this blog post from Crutchfield.