Battery Wiring on Two Guys Garage Factory Five '33

We have had a lot of people ask about how we routed power from the battery on the Factory Five '33 that we wired on Two Guys Garage. That part wasn't clear on the show. Here’s how we wired everything from the battery, including the disconnect.

First, we set aside the 4-AWG gauge wire that came with the Factory Five kit. Most people don’t realize that for the first few milliseconds after you start to crank the motor, the starter can be drawing up to 1,500 amps. That much current flowing through long, undersized cable from the battery can drop a lot of voltage. Sometimes this can be 6 to 7 volts right when the ECU needs it the most. Here’s where we tell guys not to skimp on cost & weight.

We got a good length of 00 gauge cable and ran it from the battery to a primary 500-amp fuse. This length of wire is pretty short. The goal is always to minimize the length of unprotected wire. From there we went to a good high-current disconnect switch. Here’s another place where getting cheap can hurt guys. First, you need to make sure that the disconnect can handle the steady-state current draw of the battery. Look for disconnects that have a continuous-duty rating of 150 to 200-amps at 12-volts.

Second, run the starter current through the disconnect switch with caution. Starter solenoids only draw current when they are energized so you don't have to include them in the disconnected part of the power feed. The way we wired the '33 doesn't run the starter current through the disconnect but the car is still completely disconnected when you open the switch.

If you are going to include the starter cable on the disconnect, make sure that the switch that you choose has an intermittent rating of 1,500 to 2,000 amps.

We connected the rest of the 00 gauge length and ran it to the starter in the front of the car. We also connected the included length of 4 AWG cable to the switch and ran that the common buss bar on the Mega holder block that include in the ISIS 3-Cell Kit. We connected the 2 pairs of 8-AWG wires to the fuse holders and ran one set to each POWERCELL. You can get this schematic off of the ISIS Intelligent Multiplex System website.