DC voltages at long distance from battery
Any real conductor has an effective resistance per unit length. The voltage drop over that length of conductor, and the power dissipated in that conductor, is dependent on the amount of current you draw through that conductor. For a current draw of I, and a Resistance per Meter R you will experience:

(I^2 * R) watts per meter of power lost as heat in the conductor 

and 

(I * R) voltage drop per meter of conductor

If your endpoints cannot tolerate the worst case voltage drop, or if your power budget does not account for the losses in the cable, you can expect them not to function as intended.

This PDF is a reference I have used for stranded wire.