What size wire from back of alt to battery in trunk?

[406Monte]

Thanks guys, I have the relay at the pump already from the initial install a while back. I just want to get the ground wire and alr wire diameter right...I am tired of fluctuating volt gauge.

Can I get the welder ground wire from a Home Depot or Lowes? I have no ACE Hardware around here to get it, or welding supply shops.

 

[Robert1320]

I have seen the 2ga with the red cover at Lowes before.
If you can't find cable 2ga black is only about $2 a foot.