What gauge wire?

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Will your controller support a second panel?

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Assuming you're connecting the panels in parallel, the distance is 35' one way and PWM controller then 10ga would give you a 1.5V drop plus the additional drop to the battery.

You might want to consider a combiner box and then 8 ga to the controller. You should get more information if you post all of the details like controller type, all existing wiring lengths and gauge and panel specs.

Assuming you're connecting the panels in parallel, the distance is 35' one way and PWM controller then 10ga would give you a 1.5V drop plus the additional drop to the battery.

You might want to consider a combiner box and then 8 ga to the controller. You should get more information if you post all of the details - controller type, panel specs and all involved wiring lengths and existing wire size.

The "run" is the one-way distance? Panels in series 9a, 44V; in parallel 18a, 22v

This calculator uses the one-way distance so it is easy to use

http://www.calculator.net/voltage-drop-calculator.html?material=copper&wiresize=2.061&voltage=12&phase=dc&noofconductor=1&distance=35&distanceunit=feet&amperes=18&x=49&y=10