Voltage drop 12AWG into 10AWG?

[Tomthumb62]

I have two portable panels with 25 feet of 12AWG copper clad aluminum wire. I want to replace the CCA with pure copper.

The panel mc4 leads (5 feet) are 12AWG. If I then splice those into 35 feet of 10AWG will I still have much voltage drop? Or is it worth it to try to rewire the panels from the junction box to replace the 5’ of 12AWG with 10AWG as well?

I’m trying to learn if it makes a difference which end of the run of wire the smaller gauge wire is?

 

[sunshine_eggo]

That's fine. Doesn't make any difference which end. You get a voltage drop for the 5' section and a voltage drop for the 35' section.

Provided the 12awg is adequate for the panels, I wouldn't consider rewiring.

"Estimated Resistance" tab on:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Just run the two scenarios separately and add the voltage drop. That calculator only considers one way direction, i.e., if your panels are 40' away from the controller, you'll need 80' of wire, but you only enter 40' in the calculator.

 

[Tomthumb62]

That's fine. Doesn't make any difference which end. You get a voltage drop for the 5' section and a voltage drop for the 35' section.

Provided the 12awg is adequate for the panels, I wouldn't consider rewiring.

"Estimated Resistance" tab on:

Voltage Drop Calculator

This free voltage drop calculator estimates the voltage drop of an electrical circuit based on the wire size, distance, and anticipated load current.

www.calculator.net

Just run the two scenarios separately and add the voltage drop. That calculator only considers one way direction, i.e., if your panels are 40' away from the controller, you'll need 80' of wire, but you only enter 40' in the calculator.

Thanks for that calculator, it’s much better than the one I was using (which only allowed the choice of 12, 24 or 48v).

I did the math and I come up with 6.4% voltage drop over 5’ of 12awg and 40’ 10awg at 18v and 10A. That’s acceptable to me. And yes I doubled the lengths to 10’ and 80’ for the calculator.

Much appreciated @sunshine_eggo !