For 3% Voltage Drop, at 12VDC nominal:
A 4/0 Cu cable is suitable for about 690 Amps at 10 feet total cable length (Positive + Negative).
At 15 feet total length, it's suitable for about 460 Amps.
At 15 foot distance, hence 30 feet total cable length (15' Pos + 15' Neg), it's good for about 230 Amps.
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"