Why should I do the "Big 3" and what exactly does it do I know alot of us members have quite a few electrical components running off factory wiring and our factory alternator. Hid's, Amps, Winches, Aftermarket HU's, Off Road Lights, Power inverters, CB's, etc. Hence, I thought it could be very useful to find a place to show members the proper way to upgrade "The Big 3" to help out with the electrical load; I've been trying to find some info on the amps of our factory alt. but have yet to find a reliable source, so I would assume its in the range of 100-130 amps. With that in mind, a 100 amp alternators can only send as much current as the wiring allows. This means our factory wiring is relying on ~6 ga wiring to transfer current to everything in the truck. Mathematically, this would mean; (this is running at full capacity) note: anything over, and your alt. will be unable to run your components and effective charge your batteries. The alt. needs to be somewhat > than the power you are pulling. Alts. are rated mainly at max ouput and not at idle. So consider this when doing your install and choosing an alt. Here are the specs I calculated; Amps = Watts / Volts For a 100 amp Alt, you could get approx. 1440.000000 watts For a 130 amp Alt, you could get approx. 1872.000000 And a 180 aftermarket alt. 2592.000000 Also note; no conductor is 100% efficient, but larger AWG wire helps to overcome resistance and transfer greater amounts of amperes throughout the system with smaller losses in energy. This is why people generally do the "big 3". One more thing; I know this is a readily talked about topic, but your alternators primary purpose is not to charge your battery. It is made specifically to run all your electrical components such that your battery doesn't need to. Sure, your altenator charges the battery when current is available, but that is not its primary purpose. This is why when your alt. dies, your battery can only run the entire system for a very short time (its not a deep cell). The batteries main purpose is to help regulate spikes in voltage coming from the alt, and to crank the truck. And only when your alt. cant supply the system does your battery get used. The information and description below was provided by mblouir from the how to section for the 04-08 model's. The process is the same for our model's so I used his overview. How to Upgrade the Big 3 Note: This information is all over the web. If you’ve done research on it then you will recall most of the things I mention here. This isn’t something that I invented--it’s what I’ve learned by researching. What exactly is the “Big 3”? When someone refers to the Big 3 they are referring to upgrading the three main electrical wires in the vehicle’s system: 1. Battery (+) to alternator power wire 2. Battery (-) to ground 3. Engine block to ground Why should I do this upgrade? Our vehicle’s stock electrical systems were designed for such---stock electrical. When you start adding things like audio equipment (amplifiers), aftermarket lights, etc, you are increasing the demand put on your electrical system. Upgrading the Big 3 decreases the resistance in the electrical system. Less resistance means better flowing current which means lower or even non-existent voltage drops. Most of the time stock wiring is right around 8 awg (give or take). It’s simply not designed for the extra current draw required by aftermarket items. Let’s use a garden hose as an analogy to electrical wiring. If you have a long, thin garden hose, the flow of water through it will be much less than a short, thick hose. Compare a 100-ft, 5/8” diameter garden hose to a 1-ft long, 6” diameter section of water supply PVC pipe. The flow will be much greater through the shorter, thicker section (less pressure). The same goes for electrical systems. The larger and shorter your wiring, the less resistance to the flow of current. Even if you do not have any issues with voltage drops, dimming headlights, or anything like that, the Big 3 is still highly recommended. Stock electrical systems can benefit from the Big 3. It’s probably the cheapest upgrade one can do for their electrical system. While it’s generally recommended to use 4 awg or larger wiring for upgrading the Big 3, I highly recommend using 1/0 from the start. It’s the best option and only costs slightly more. Better to do it right the first time. How to upgrade the Big 3 Note: The following is the method I used and the materials I used. If you have a different tool or method feel free to use it---as long as it gets the job done safely. What you need I highly recommend welding cable for this "how to"! It is super flexible and you do not need any plastic covers. It is highly durable and over 99% copper. Please be aware any wire containing ALUMINUM is not a good choice. Although the aluminum clad wire is cheaper, it does not conduct nearly as good as copper. So choose your materials appropriately. • Approximately 10 feet of flexible 1/0 high-strand wire (measure your vehicle’s existing wiring with a string to be sure, and overestimate) • Six (6) 1/0 ring terminals • In-line ANL fuse holder • ANL fuse rated between 200 and 300 amps (I used 250A) • Wire brush to clean contact points • Extended battery posts for ring terminals • Wire cutters large enough for 1/0 • Knife or wire strippers large enough for 1/0 • Crimpers large enough for 1/0 • Solder • Propane torch or soldering gun • Socket set for bolted connections • Allen wrench set for connecting fuse • Zip-ties I wont go over how to attach ring terminals or install fuses, but this will give you an overview of how and where to attach the necessary wires.