Quote Originally Posted by firebird77clone View Post
Check your local metal scrap yard. They'll sell you wire priced by the pound and you'll save big bucks over new. No guarantee they'll have exactly what you need, but it might be worth a look.
There are places where saving a few bucks by using salvage is OK, but insulated cable for battery connections is not one I'd feel comfortable with. Like Matthyj says, welding cable has lots of little strands of copper and is very flexible, making it much, much easier to work with. It also has insulation that's generally rated for 600 volts, and is thermoset as opposed to thermoplastic, more resistant to abrasion. I'd recommend that you do it with new, top quality cable and know that it's right.