How is DC cable sizing and voltage drop calculated? (WIP)

Easy PV returns the smallest cable cross-sectional area that achieves a voltage drop less than 1% of the voltage across the cable (or the largest cable if none do).

The voltage drop along a cable is the product of the current running through it and its resistance. We calculate cable resistances using the stranding class 1 and 2 values from the IEC 60228/BS 6360 stranding chart. 

Example calculation

Adapt example from cable calcs here: https://docs.google.com/spreadsheets/d/1me9UIuyPfioQQbOrTBsFxSda4AY5mMhxSHBCOlgdLqw/edit?gid=0#gid=0