Solar Panel to Charge Controller Cable Size

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Link to the voltage drop calculator: https://www.calculator.net/voltage-drop-calculator.html

In this video I correct a mistake I made in a previous solar wiring video and in my book. I walk you through the proper way to size the PV cable between your solar panels and the MPPT charge controller, focusing on the difference between using Isc × 1.56 and Isc × 1.25. You’ll see how this impacts the voltage drop calculation, the final PV wire size, and how much you actually spend on copper in your off grid solar system.

I use a real example with two 200W solar panels in series to show you step by step how to work out the string voltage, the cable ampacity and the acceptable voltage drop. We compare the old method, where I used Isc × 1.56 for everything, with the corrected method, where we still use Isc × 1.56 for ampacity but only Isc × 1.25 for the solar voltage drop calculation. This simple change can let you go from 8 AWG to 10 AWG on the PV run, while staying completely safe and within the current ratings of the cable.

I’ll also talk about why the PV-to-MPPT cable is usually the longest and most critical run in an off grid solar setup, why high DC voltage can be dangerous if you wire panels in series, and a simple safety sequence to follow when connecting your solar panels, PV disconnect and battery. If you’re interested in topics like PV cable sizing, solar wire size, MPPT charge controller wiring, off grid solar design and voltage drop calculation, this video will help you clean up your method and save some money on your next installation.