How To: The BIG Three, The Big 3 Wiring Upgrade

I know some of us have done the Big 3 electrical wiring upgrade or plan to do it sometime in the future.

For those of you who haven't done this yet, but would like some info on why or how to do this, here's the thread to gain some useful info.

Basically what this involves is increasing the size of the wire used to allow the electrical current to have an easier path & more copper wire for that current to flow through.
Imagine trying to water your lawn with a straw... the water would certainly come out the straw, but not very much would come out. Now imagine watering your lawn with a fire hose... lots of water with more force would come out & you'd have your lawn watered in very little time.

You will be changing:
1. the Power wire from the Alternator to the Battery
2. the Ground wire from the battery to the chassis/frame
3. the Power wire from the battery to the main fuse/relay box.

Most stock Rangers will have a Fusible link between the alternator and battery. This is to protect the battery in case the alternator outputs way more power than it should. It acts like a fuse. When doing the Big 3, you'll want to install a new heavy duty fuse holder that will accept the wire size you are using for the upgrade and use a fuse that is slightly larger than the total output amps of your alternator. For instance if you have a 200a alternator, a 225a or 250a fuse should work. The slight overage on the fuse size will help avoid any prematurely blown fuses due to normal spikes. You can also use the same size fuse as your alternator's output.

If you have stereo amplifiers, etc that will require high current, you'll want to upgrade those wires as well.

I'll use my truck as an example, since I remember most of the steps I used

First I bought my 200 amp alternator.

Next I drew the layout I wanted & calculated the number of crimp terminals I'd need. I then went out to the truck with some string to measure for all the wire I would need. I don't remember how much wire I used, but I bought about 25% more than I knew I'd need just in case something went wrong or if I changed the routing of the wires.
I opted to use 1/0ga wire for my Big 3. I could have probably used 4ga, but at the time 1/0ga wasn't that much more & I didn't want to have to do this over again so I went BIG.

Once I had the alternator, all the connectors & wire, I started running the wires to their locations & cutting them to length.

After all the wires were cut to length, I slid the heat shrink tubing over the ends of the wire & I started attaching the crimp terminals. I used 1/0ga wire (that's actually a little larger than 1/0ga) so I had a fun time getting each & every terminal over the wire. I crimped each terminal using the largest crimping tool I had, as well as any other method I could think of to securely attach each terminal. You could also solder the terminals on after they have been crimped for an even more secure connection, although no ordinary solder iron or solder gun will be able to heat the large diameter wire properly, so a torch of some sort will be in order.

After each terminal was connected, I slid the heat shrink over the connection & heated it up to make a nice looking connection.

I started at the alternator's Power output with a terminal that had a 1/4" inside diameter hole to fit the bolt on the alternator, then carefully routed the wire in & around following the OEM wire's path. I connected the other end to one side of my heavy duty wafer fuse holder & attached the fuse holder to the inner fender.
I then attached a connector to the other side of the fuse holder & routed it up to the Positive battery terminal.
Next I ran a wire from my Positive battery terminal back to my main fuse/relay panel under the hood, I believe this also used a 1/4" inside diameter terminal. I left the fuse out until everything was connected for safety.

I went a bit beyond the basic Big 3 and also upgraded the wire from my battery to the starter with 4ga wire. While this isn't always necessary, my stock starter wire was only about 6ga & since I had the extra 4ga wire, I upgraded that as well.

Next I attached a ground wire to the Negative battery terminal and connected it to the header panel in front of the battery where the OEM ground connection was. I then attached a 2nd ground wire to the Negative battery terminal and connected it to the frame of the vehicle. I then connected the body & frame grounds with another piece of 1/0ga wire.
Most times you should be able to use a single wire from the battery to frame & frame to chassis, but I had the wire & went a little overboard.
The main thing to remember is that your grounds are just as important as the power wires.

It isn't necessary to run a ground wire to the alternator itself as the alternator will physically ground to the motor and the motor should be grounded to the chassis & the chassis grounded to the body. Some people have used a ground wire directly to the alternator & there shouldn't be any disadvantage to doing this aside from requiring a bit more wire.

I had also provisioned for a 1/0ga wire to run inside the truck for my amps & any other accessory I might want to connect. I had to drill a large hole in the firewall for a special waterproof grommet made for the 1/0ga wire. I ran a beat of 100% silicone caulk around both sides of the hole before installing the grommet to ensure no leaks.

After all the wires were connected & wrapped in wire loom to protect them, I installed the fuse between the alternator & battery.

To make sure everything was working properly, I started the truck & checked the voltage at the alternator, battery & at the cigarette lighter in the truck. All read 14v or more when the truck was running which is just what we want.

Big 3 completed.

My Big 3 upgrade went a bit beyond the normal Big 3... guess I could call mine the HUGE 3 upgrade.