Battery Relocation

When doing a battery relocation from the front to the rear I have been told that the diameter has to increase . Is there a way to calculate how thicker I have to go ? Also does this apply when relocating from the front placement (example near firewall) and move it in front/lower where the bumper is (on ff drag cars) ?

G'day James.

You usually go to a larger main power cable due to the increased length, as the battery is now much further from the starter motor. For the FF drag application the battery wont usually be a huge amount further away from the original position, so stepping up a cable size might not be required.

What is the application? For a high compression engine that is going to take a bit of cranking I'll usually step to 50mm^2 cable if the battery cable has to run the length of the vehicle.