DIY Relay Box Wiring

Was hoping some electrical pros could help out here and double check my work in terms of safety!

I'm currently wiring up a 6 gang relay box so that I can have better/safer distribution of power to light bars and such on my truck, but I'm not 100% certain that this is the proper way to go about. In short, I have a 12 gauge wire I plan to run from the battery into the relay box. From there, I split the power by tying in 14awg wire into the 12 awg, with each segment of 14awg going into one part of the relay as the power source. From there, the relay will then have another 14awg wire that goes out to a fuse, which then will also use 14awg to power whatever device I choose. My main concern is whether or not splitting off power from 1 12awg wire is the way to go, or should I have 6 separate power wires going in from the battery to the relays?

Thanks in advance!

 

No reason you can’t use a single wire to power the entire relay bank. Several aftermarket relay banks do this but it sounds like you want to build your own.

The 6 loads and their power consumption is what’s important here. That dictates wire size, relay size, fuse size.

I would recommend one big fuse between the battery and relay box as added protection. The way your diagram is setup each load has a protection device between it and the relay box, but if somthing every goes south in the relay box you have no protection back to the battery. It would be an added safety measure.

Fuse size would need to be big enough it wouldn’t blow when all 6 loads are running at the same time.

Running an individual power wire from the battery for each relay would be wasteful. As long as you size the single wire right and have proper protection from shorts ect you should be good to go.

 

Always have a fuse closest to the battery as possible.
If you’re just doing lights and other low powered devices then that one 12awg wire is enough. The amount of power consumption and distance from power source dictates wire gauge. But in my experience 12awg has been plenty, even for wiring things near the rear of the truck.

Edit: reason for fusing nearest to power source is if you get in a car accident and the wire gets shorted before the nearest upstream fuse and causes a fire.

 

Yes think of the wire as an extension of the battery post. The closer the fuse is to the battery the more of the circuit you protect.

I would also recommend mounting the relay bank in the engine bay in the general area of the battery. In general the shorter your high load power wires the better.