Voltage doesn't matter for wire size, amps do. 14 gauge will do 15 amps, 12 gauge is for 20 amps, and 10 gauge is for 30 amps. After that I have to look it up but I think 8ga = 40A. Keep in mind you shouldn't plan to sustain >80% load, so to run a continuous 30A load you need an 8ga wire, but a short peak is fine on a 10ga wire so long as the continuous load is <=24A.This is kind of a hypothetical but I’m working on a project where the answer will help me a bit. So I would appreciate any input to help me learn.
If a run two wires back from my battery to my cargo area (one for positive and one for negative) and connect these to a DC-DC converter to increase the voltage to 24V.
30 amps will be going into the converter and 15 will be going out as the voltage is doubled.
When I’m considering the gauge of the wire from and to the battery, I know the blue sea systems wire chart is meant to consider the full length of the circuit (out and back), but could I make the negative wire going back to the battery smaller gauge since in will be only half of the amperage at that point?
And yes, I fear this question highlights a complete misunderstanding of the way electricity works….
Now if you're DC-DC converting to 24V, then your 24V loop (+ from the converter to the device(s), - going back to the converter) could be 14ga, but the 12V run to and from the converter should be 10ga minimum (and probably 8ga if you're going to sustain 30A).
BTW on the 12V side if your DC-DC converter is in the trunk you can ground to the body (i.e. a 3rd row seat bolt) and that effectively increases your return wire gauge since that ground is going to be way thicker than any wire you run.