welding wire is much better in my mind for battery relocation than what comes with the kits, the individual wires are much smaller making a super flexible cable, the insuation is silicone not plastic to it can take alot of heat, if you solder the ends on you will need alot of solder to penetrate the wire, i recomend measureing and having the ends crimped on, crimping is better than soldering for high vibration areas like an engine, it doesn't concentrate the stress at the end of the connection or make the wire inflexible like solder does when it permiates up the wire, in case you wanted to know
grant