cable sizing

I dunno......Depends on the type of cable!!

resistance of your length of cable will be:

r=ρl/a

where ρ is the resistivity of the medium (probably copper, in which case 1.75E-08)

l is the length in metres

a is the cross sectional area of your cable (in square metres).

The voltage drop will be v=ir, where i is your load amps.

You can see that for a long cable, its thickness is the key to a low voltage drop at high amps - tradeoff is that copper is not cheap...